Book Review: Vicki Hird, Rebugging the Planet

Vicki Hird, Rebugging the Planet:

The Remarkable Things that Insects (and Other Invertebrates) Do – And Why We Need to Love Them More

Chelsea Green Publishing, September 2021, 224 pages, $17.95

Vicki Hird has a passion for insects, and this book brings home to us how much depends on the well-being of invertebrates in the world. Insects are a cornerstone in our ecosystem, and we must reverse the current dangerous decline in bug populations (40% of insect species are at risk of extinction and 33% more are endangered). We are heading towards “Insectageddon.” After reading this book, I found myself being much more careful about gathering up insects inside the house and taking them outside, where I imagine they will thrive better. Did you know that spiders rest calmly in your gently closed hand? They do not wriggle and tickle!

We need to overcome any aversion or indifference to creepy-crawlies, and change our attitudes to respect, appreciation, and some humility if possible. Insects pollinate plants, recycle waste into nutrients, control pest species, add air channels in the soil, and ultimately return themselves to the soil food web.

Fall spiderweb photo from Ezra Freeman

Vicki explains how to rebug our city green spaces, grow gardens without pesticides and weedkiller, teach children to appreciate small creatures, make choices that support insect-friendly (planet-friendly) production of food and fiber, and make wider choices that affirm human dignity and equal rights.

This book has charming insect drawings, and delightful anecdotes: “I was never going to get the pony I wanted, so I settled for an ant farm at an early age.” Studying biology at school led Vicki to a summer job observing bees at a research station. A later job investigating cockroaches led her to respect them and realize that it is humans that need better control, more than roaches do.

Vicki has been an environmental campaigner, lobbyist and researcher for about 30 years, and is the mother of two children. Vicki is also head of the Sustainable Farming Campaign for Sustain: The Alliance for Better Food and Farming, a UK alliance of organizations and communities advocating for healthy food, people and environment, and equity in society. She has a website for Rebugging.

Those over 50 (and maybe 40) will have noticed that long car drives no longer lead to cars covered in smashed bugs. There are fewer butterflies. More than twice as many insect species as vertebrate species are at risk of extinction. I noticed on a trip to England after an absence of a couple of years, that the number of sparrows has plummeted. We are more likely to get distressed about the charismatic mega-fauna, but less so about formerly ubiquitous sparrows, and even less about insects. There may be 4 million unidentified species of insects (as well as the million we know). In the UK 23 bee and wasp species have become extinct since 1850.

So, what is ‘rebugging’? It is a form of rewilding (the introduction of similar-to-natural ecosystems and missing species into an area and then waiting to see if the species can settle in). It is somewhat controversial, and alone is insufficient to cause all the changes we seek. We also need changes in policy, lifestyle, and civic involvement. This book provides information, encouragement and tools to act.

Sunflower bee and bug.
Photo by Bridget Aleshire

What would the world be like without bugs? “A great image that has been doing the rounds is a picture of a bee saying, “If we die, we’re taking you with us.” It’s not an empty threat, but a fact – we would not last long without insects. Our flowering plants would die off; all the species that dine on insects would be lost, followed by the next ones up the chain; dead animals would pile up undigested; trees would cease growing in the compacted airless soil.

But this is not our inevitable future. We can step back, as we have done when the dangers of DDT, CFCs, and nuclear weapons became blindingly clear. We can work to restore habitat, reduce damage and make political and economic structural changes at all levels in society. We can start by “rebugging our attitudes.”

How can we protect and nurture invertebrates? We can help research what’s out there. We can encourage others to be concerned and take action to protect invertebrates. We can teach others about the value of insects for human well-being. We can make havens for wildlife, convert every city street into a biocorridor, share designs for pollinator-friendly gardens, encourage conservation of water and other natural resources, make urban farms and community gardens.

The book is studded with sidebars on aspects of the value of insects, such as “How much is a bee worth?” (The answer is over $3,000 per hectare in pollination services, for wild bees) That’s more than 651 million GBP to the British economy.

Insects are food for many animals such as poultry, fish and pigs. And some insects could be food for humans. I ate a 17-year cicada last time they were in our area (2013). I was partly inspired by Jackson Landers’ book Eating Aliens. And really, if you can eat shrimp, you can eat meaty insects. But Rebugging isn’t mostly about eating insects, but rather preserving their lives, and benefiting from their contributions.

If you are still unsure what bugs do for us, the second chapter spells it out. We would be knee-deep in manure, leaf litter and dead animals within weeks, if there were no bugs eating it all, and enriching the soil. Tardigrades (water bears or moss piglets) are the most resilient animals known, able to survive extreme temperatures, pressures, dehydration, oxygen deprivation, starvation and radiation. They can remain in suspended animation for years until conditions improve. They have already survived all five mass extinction events, and some have been revived from a hundred-year-old sample of moss in a museum. Respect, please!

A ladybug on the leaf stem of a sunflower planted to attract beneficials.
Photo Pam Dawling

Avoid spraying wasps with pesticides-in-a-spray-can. They are as useful as bees and ladybugs, and are the best pest control we have for hauling away cabbage caterpillars. If you are more motivated to provide accommodation for ladybugs than wasps, keep moist dark places like old hollow stems, bark pieces and logs where the adults can overwinter. I could really use some early-spring-wakening ladybugs in our hoophouse to tackle the aphids!

Carefully introduced biological bug control can reduce the amount of pesticides used. A scientific risk assessment is an important first step, though. The 1930’s introduction of cane toads in Australia for pest control was a terrible mistake. The toad was a worse pest than the bugs had been. There are many more success stories than disasters!

Vicki Hird, Author of Rebugging the Planet

Rewilding can be complicated – looking at a huge overgrowth of creeping thistle is alarming. Happily, the biggest migration of painted lady butterflies came over and laid eggs on the thistles. The resulting spiny black caterpillars ate the thistles down to the ground. UK organizations have been creating maps of “insect superhighways” they are calling B-Lines, that will be filled with wildflowers so that insects and other wildlife have continuous corridors to travel from one area to another. There’s a two-page spread of possible actions to help the rebugging process, starting with publicity and education, and moving onto helping build bug-friendly habitat in public places and workplaces and private gardens.

Green public spaces can include a wide variety of invertebrate species. Look on derelict land, in cemeteries, along grass verges, and even on golf courses. Many companies and local authorities are now wanting to manage their land in ways that support more wildlife, and with encouragement might move another step in that direction. Tiny public orchards and forests are being planted in some places. There is a sidebar of actions to reduce deliberate, accidental, and thoughtless damage to insects.

After starting small and local, you might be ready to expand your ambitions and commitment. The overall total mass of insects is estimated to be falling by 2.5% every year. One big factor pushing species towards disaster is climate change. This is a big one to tackle, and yet we must. Overwintering numbers of monarch butterflies (the celebrities of the insect world) have dropped to less than 1% of their 1980’s population. Yes, compared with 40 years ago, the population is now just 1/100 of what it was. When food species arrive, peak, or leave earlier in the year due to changed temperatures, the predator species goes undernourished. Pesticide contamination gets a lot of blame too.

A bee pollinating squash. Photo Pam Dawling

Water pollution also harms diversity. Leached fertilizers in estuaries have created ocean dead zones. Combating climate change might not be what you expected to read about when picking up a book on rebugging the planet, but it is vitally connected. We can learn from bugs about climate management. Honeybees have learned how to mob an invading Asian giant hornet and cook it to death. In Brazil, scientists discovered an area of 200 million termite mounds each spaced 60 feet from its neighbors. This is all one colony, connected underground. Some of the mounds are over 4,000 years old. They have created a stable environment for millennia. The methods of ventilation and gas exchange could be copied for human habitation.

Are 5G phones heating insects 370% above normal levels and cooking them in the electromagnetic fields they generate? It could be true, based on research on models. The action list at the end of this chapter urges us to avoid 5G phones if we can, and not to use them outdoors if we must have one.

The chapter on why our farming, food and shopping all need bugs opens with a discussion on almond milk. The “dark reality” is that huge almond plantations need millions of bees brought in every year for pollination. Thousands of colonies are moved in to California’s Central Valley, for example. 30% of these bees die, because the environment is hostile, devoid of crops other than almond trees. Local wildlife cannot survive either.

It is a mistake to think that all vegan milk-substitutes are environmentally better than all dairy milk. It takes roughly 4 gallons of water for every gallon of milk a cow produces. Almond milk is much more intensive on water use: it can take up to 101 gallons of water to grow 1 cup of almonds, plus another 3 or 4 cups of water to manufacture almond milk. In fact, many commercial almond milks only have about 2% of almonds in them – the rest is water!

Bugs and other small animals can thrive in pastures if the livestock management is done well. The stock numbers and types are important.

Did you know that more than 70% of the world’s fish stocks are over-fished, depleted or collapsed?

We could also consider the impact of our decisions about textiles, timber and metals, on wildlife and ecology. The average person in the UK now buys over four clothing items a month! Less than 1% of clothing textiles is recycled. The waste mounts up. Forests are destroyed to make way for cotton plantations. Even if organically grown, cotton monocultures destroy habitat of thousands of species of butterflies, moths, termites, wasps, bees, and other bugs. Ironically, the cotton crop is then a sitting target for the bollworm moth. Genetically modified cotton was developed to overcome bollworm problems. A few countries resisted the siren call of GM cotton, and use integrated pest management (IPM) instead. They have lowered costs and increased yields.

While worrying about cotton, let us not forget synthetics and the huge problem of microplastics. In 2016, for example, 65 million tons of plastic textile fibers were produced. They do not decay. They are found everywhere on the planet, from the Arctic to the ocean depths. Ingestion of microplastics causes problems for marine life. The dyes cause disease, and can kill corals.

The action list for this chapter focuses on reducing waste. Think before you buy, think before you throw away. If you can, switch to consumption of locally sustainably produced goods.

Front and back covers of Rebugging the Planet

The action lists that close each chapter get longer, the connections get wider. Politics and the economy might not be the direction you expected from this book, but these topics are all part of the connected system, and all need consideration and action. Termites and corals co-operate within their colonies to create and maintain large healthy populations: we can do it too. (Corals are symbiotic associations of bugs (coral polyps, which form the exoskeleton) with several thousand species of animals and plants living within. Algae provide oxygen and carbohydrates.)

Big investors own shares in seed companies, just to make money. They have no interest or incentive to protect bugs or any aspect of the ecology. “It’s as if some beetles decided to take all the ants’ food supplies even though they cannot eat or use them. Money accumulation is hard to eat.”

Frustratingly, vested interests have too much power in decisions that affect large groups of people. We tend to avoid tackling entrenched societal problems. Vicki suggests three big areas to understand and deal with: poor governance and politics; inequality and poverty; runaway consumerism and waste. If you only wanted to read about saving beetles, you might be tempted to put the book down at this point. However, in order to save beetles, we need to look at the underlying causes of beetle die-offs.

Decisions on land use are often made by corporations and investors less focused on protecting biodiversity, and more on profits. We need to show them that enlightened self-interest can protect their financial success for the long haul. Some corporations are seeing this now that climate chaos is biting hard. Pushing humans to get three-quarters of their calories from just four crops (soy, wheat, rice and maize) may bring in fast bucks, but gives little resilience against climate change and extreme weather conditions, and is bad news for biodiversity.

Research has shown that as social inequality grows, so does harm to biodiversity, which leads to more inequality. Financial pressure from profit-seekers drives down wages, leading to a demand for ever cheaper food, spiraling to lower costs of production. They wring out higher short-term yields. Sustainability of food production goes to the wall. Desperate people take desperate measures to cover their basic survival needs. In 2020, the UN announced: “to bend the curve of biodiversity loss, we need to bend the curve of inequality.”

The action list for this chapter is over 5 pages, demonstrating the broadening of the goals. Campaigning, lobbying and voting; pushing governments and economists to balance social and environmental concerns and work for sustainable outcomes; requiring corporations to show much stronger accountability for all the results of their activity; supporting companies that are taking steps to lower their environmental damage and increase co-operation with others, strengthen international treaties and hold nations to their commitments on biodiversity and limiting climate change.

This probably sounds overwhelming, but “You don’t have to rebug alone”! You can join (or start) local organizations working on an issue you feel strongly about. The book contains a directory of some organizations (mostly in the UK). There is some help on starting lobbying, which most of us have not done before. The resources include guides on campaigning and influencing people. You can reduce your own carbon footprint and encourage others to do so. Big change is needed, but some days it’s restorative to “clean our own house” rather than go out lobbying.

 

Book Review: Sally Morgan, The Healthy Vegetable Garden

The Healthy Vegetable Garden
Photo Chelsea Green

Book Review: Sally Morgan, The Healthy Vegetable Garden: A natural, chemical-free approach to soil, biodiversity and managing pests and diseases.

Chelsea Green Publishing, September 2021

Sally Morgan is an expert organic gardener in the UK. She is the editor of Organic Farming Magazine for the Soil Association, the nation’s foremost non-profit organic gardening and farming membership organization. Her book The Healthy Vegetable Garden is clearly and concisely written. Sally promotes building healthy soil, boosting biodiversity, creating habitats to attract pollinators and predators, making good use of water, promoting the stability and resilience of natural ecosystems, and integrating the landscape with people.

A healthy garden maintains a balance where pest organisms are at a non-damaging level, (rather than eliminated entirely). Here you will find lots of solid information to identify pests and diseases and deal with them using regenerative principles, and when necessary, making traps and lures.

The book has some info particularly for US gardeners – you’ll be able to read about Mexican bean beetle and Colorado potato beetle! You might be mystified by some of the European details we don’t have to deal with, such as raspberry beetle or flatworms. As long as you have some prior gardening experience where you live now, you can only benefit from the information offered here. Brand new US gardeners might get confused.

The Healthy Vegetable Garden has good descriptions of soil and its components, structure, assessment, and testing. It is important to nurture healthy soils producing healthy plants, with the essential minerals and vitamins we need for health. Nutrient density has declined seriously over the last 70 years, particularly levels of calcium, iron and vitamins B and C. In 2014, the UN warned that we had only 60 years of harvests left, if we continued degrading our soils. In 2020 a new study estimated that 90% of soils had only 100 years of harvests left. Soils managed with conservation techniques have much longer projected lifespans.

The second chapter is about ways to regenerate soils, by minimizing tilling or digging, adding compost, mulches and cover crops. The living mulch section is where I am hesitant. My experience and that of Jesse Frost whose Living Soil Handbook I reviewed recently, is that living mulches can out-compete the crop if we are not skilled and careful. The author does point out the need to cut back the mulch to prevent this problem. Growers in the south might find planting zucchini (courgettes) into white clover impractical as zucchini is a fast-turnaround crop for us, whereas clover is a slow-growing cover crop. The author leaves the clover growing through the following winter, to make the combo work. In the chillier parts of the UK, only one crop of zucchini can be grown in a summer, so the system makes sense. In Virginia, we plant zucchini and summer squash 5 times outdoors. Likewise, the speed with which chickweed flowers and sets seed in Virginia would make it unwise to regard it as a cover crop! I did like the idea of undersowing tomatoes with coriander, if I wanted large volumes of coriander (cilantro).

Chickweed flowers.
http://ipm.ucanr.edu/PMG/S/W-CP-SMED-FL.006.html
Photo by Jack Kelly Clark.

The chapter on understanding pests and diseases is well-written, although we in the US have so many more than in the UK! Plant pests are listed in categories by their method of causing harm, rather than by individual names, which helps understanding. Plant pathogens likewise are described by type, as bacteria, viruses, fungi, water-molds. Fungal pathogens include biotrophs (parasitic pathogens such as downy mildews, rusts and smuts), semi-biotrophs that spend part of their lifecycle on the host, then part feeding saprophytically on the host’s dead remains (such as apple scab, Phytophthora blights, Botrytis-type molds and powdery mildews) and necrotrophs that kill their host and then feed as saprophytes. I appreciated the bigger understanding this classification of pathogenic fungi gave me.

Heed the warning that climate change is bringing new pests and diseases, and the chilling news that for every 1 Celsius degree rise in average temperature (about 2 F degrees), aphids become active two weeks earlier. Some warm climate diseases will move further towards the poles. The author recommends paying attention, encouraging good airflow around plants, sanitizing pruning tools, and planting rows of tall plants to break up the progress of air-borne fungal spores.  Growing potatoes downwind of a row of Jerusalem artichokes is a good example.

Sally is very practical on the subject of sterilizing pots and flats – your tools, boots, gloves and hands are as likely to spread spores, don’t worry about sterilizing pots! Some of the disinfectants suggested in other books can do more damage! Likewise, most spores don’t survive long on the ground, removed from their host plants, and so such diseased crops can be safely composted in a hot compost process. Practice crop rotation to deplete those that do survive in the soil, such as carrot rust flies.

Under normal conditions, predators can prevent pest outbreaks, but problems arise when conditions change quickly and disrupt the balance of prey and predator. If you see lots of pests, find a way to deal with them that won’t also kill their predators and parasites. Beware broad spectrum pesticides and fungicides, even if Organic. Encourage ladybugs and beetles by creating “ladybug hotels” and “beetle banks”. (There are some photos to inspire you.)

Plant for a continuous supply of insect-attracting blooms. Yarrow, ajuga, alyssum, dill, and fennel flower early in the year and attract predators like hoverflies, ladybugs, lacewings, tachinid flies, and parasitic wasps. Also grow early blooming flowers with pollen and nectar predators can use as alternative foods – borage is fast at producing nectar, as are dandelions. Phacelia is a very attractive to predators, especially aphid predators like hoverflies and parasitic wasps. Sow in the fall for early spring blooms. Angelica is a biennial that can flower in the spring of its second year. If you decide to trust to weeds to feed your beneficial insects, take care about how much seed they sow! This is a risk I do not recommend taking, especially in warm climates with rapid rates of growth.

Borage in an insectary circle.
Photo by Bridget Aleshire.

In the section on crop rotations, polyculture and continuous cropping, Sally reports that she has moved away from a rigid crop rotation for many crops, following Elaine Ingham’s observation that nature does not rotate. This may be a place where home gardeners and production gardeners diverge. Mixed beds with several crops work well for manual work, but less so for those with rototillers, or even those hoping to make fast progress with a scuffle hoe. Mixed plantings are attractive and fun for the solo gardener, but having others pull up your delightful medley suggests it doesn’t work so well for bigger operations.

This book is not dogmatic. Rotations help disrupt pest and disease cycles, and here you can read brief descriptions of three-crop, four-crop and eight-crop rotations. You can also devise ad-hoc rotations and grow beds of different crops next to each other, in order to benefit from diversity without slowing down your hoeing or putting a bed out of commission while you wait for the last item in that bed to finish its lifecycle.

Shumei Natural Agriculture Farm, Yatesbury, Calne, in SW England has been increasing yields year by year, with no rotation, no pesticides, and no fertilizers other than material from immediately around the beds that is incorporated into the soil. You can’t successfully switch instantly to this method of growing, because it takes time and lots of the right microbes for the soil to adapt. Charles Dowding is experimenting with this at Homeacres, his garden in Somerset. Continuous cropping is a challenging idea to those of us who came up when organics was the opposite of industrial monocropping. We championed rotations.

The author provides a list of perennial vegetables she is growing: Chinese artichokes, Jerusalem artichokes, globe artichokes, Good king henry, lovage, perennial kales, scorzonera, sea beet, sea kale, skirret, Babington leeks, potato onions, walking onions, and Welsh onions. No rotation is used for these no-dig crops, which grow with a layer of leaf litter on the soil.

Sally Morgan

Agroforestry is the practice of growing vegetables in wide alleys between trees. Sally has tried this by planting a row of cordon apples (trees trained to a single stem) along the edge of a vegetable bed. US readers should not follow her exact hedge design plan, as autumn olive, blackthorn and dog rose, for example, are invasive here.

Part 4 of the book is on boosting defenses, and how biocontrol works. This is the use of one organism to control a pest or disease. It is important to learn about the pests you have and their particular biocontrols. It’s not a case of opening the bag and throwing the stuff on!  Biocontrols have specific requirements, such as temperature or moisture. Timing is important.

Parasitic wasps, minute pirate bugs and predatory mites like Phystoseilus persimilis (which eats spider mites) can be introduced for their appropriate prey. Try to save biocontrols for when you really have a problem, and make sure you correctly identify the pest you want to control.

Predatory nematodes each have their own mutualistic bacteria living in their gut. When the predatory nematode works its way into its prey, it releases its bacteria, which kill and digest the prey. Reminds me of the Trojan Horse! The process happens below ground – nothing to see here! I found this fascinating! Nematodes need a film of water to live and move in, and temperatures above 41˚F (5˚C). Buy the right nematodes (and bacteria) for each job. This book has a two-page spread on which parasitic nematode to use for which pest. I have not seen this quality of information in any other book! Nematodes can be used to manage slugs, weevils, carrot rust fly, cutworms, onion fly, gooseberry sawfly, thrips, codling moth and more.

Plants have their own protective species. The introduction to the rhizosphere (microbiome around the roots) includes fascinating details on a type of morel mushroom that farms bacteria! Soil fungi are important for most crops, except brassicas and chenopods (beets, spinach and chard). We hear about the rhizosphere, but not the phyllosphere, the equivalent collection of micro-organisms on the leaves. This is mainly, but not only, composed of bacteria. About 10 billion on one leaf, and all different from the bacteria in the soil, and varying from one crop to another! Young leaves have mostly bacteria, mature leaves have more yeasts and senescent leaves mostly filamentous fungi. These microbes protect the plant’s health, supply biofertilizers, biostimulants and biopesticides. Some leaf bacteria suppress growth in caterpillars feeding on the leaf. Understanding this helps us appreciate the reasons for not spraying plants haphazardly with things that “might help”.

Plants have an arsenal of defenses. Thorns and hairs are just the most obvious. Some plants stockpile toxins to provide fast response to insect attack, others manufacture them as needed. When attacked, many plants respond by toughening up their cell walls in the area being attacked. Plants release various volatile compounds communicating with other plants and with insects (both the pests and predators of those pests). The example given is that when corn roots are attacked by a certain larva, the roots release a compound that attracts a nematode that is a predator of that larva. Sometimes, though, the attacker wins, as when certain beetles release their own volatile compounds in response to a plant’s compounds, signaling to other beetles to join the attack. Colorado potato beetles do this. This complexity calls our interventions into question: is it helpful to handpick the pests? Not if the pests call on comrades to join the fight.

Young sweet corn plants in July. When corn roots are attacked by a certain larva, the roots release a compound that attracts a nematode that is a predator of that larva. Photo Bridget Aleshire

If your soil is already healthy and rich in microbes, Sally thinks additions are not needed, including biostimulants, compost teas and foliar sprays to boost the numbers of beneficial bacteria and fungi. Biofungicides can prevent particular soil-borne diseases, but can’t cure them after the fact. Biofumigation is the process of growing a particular cover crop, chopping it finely and incorporating it into the oil, taking advantage of the allelopathic compounds released, to kill pests, diseases or weed seeds. Mustards, radishes and forage sorghum all have bio-fumigant properties.

The chapter on barriers, lures, traps and sprays includes recipes, and the caution that many homemade sprays kill beneficials as well as pests, as do some of the Organic commercial sprays like neem, Spinosad, quassia. Use these only as a last resort, and pay attention to dilution rates, time of day to spray and frequency of use.

Here you can find instructions for carefully treating seeds with a disease-fighting hot water treatment before planting. You can also find cautions, such as not heat-treating peas, beans, corn, cucumbers, lettuce or beets. Or old seed, as the germination rate might deteriorate too far.

Part 5 of the book is an A-Z of Pests and Disease. First are aphids – there are so many kinds of aphids! The lifecycle of aphids starts in spring with eggs hatching into wingless females that give birth via parthenogenesis to more females. Within a week, one female can produce 100 clones, which can repeat the process at the age of one week.  This continues until adverse weather or predators trigger production of a generation of winged female aphids that moves to new plants. Later in summer male aphids are born and females lay fertilized eggs that overwinter on host plants, to hatch the following spring.

Pepper plant with aphids. Photo Pam Dawling

Handpicking aphids is likely impossible, so start by blasting them off the plants with a water jet from a hose. This may decrease the population enough for natural predators to begin control. Failing this, a soap spray can be effective, although aphid predators will also be harmed. If you plant before any aphids arrive, you can use a fine mesh netting to keep them off, but monitor to make sure no aphids have got inside the net. You could try trap crops of nasturtiums to draw aphids away from your crop, but how much of your space do you want to devote to nasturtiums, and how do you deal with aphids then? The same choices of water and soap.

The list of pests continues through the alphabet. For some, nasturtiums can act as a repellent rather than a trap crop. Cucumber beetles are a good example. Nasturtiums are a brassica, and will attract cabbage caterpillars if there are no other brassicas around. There are two pages on making the garden inhospitable to slugs and snails and three pages of control options including beneficial nematodes, ducks, coffee grounds (acidic and non-specific) and iron phosphate pellets.  Finally, there are whitefly and wireworms.

The disease chapter starts with various blights, including two pages on potato blight (both types). Cankers, club root, damping off fungi, mildews, molds, rots, rusts, spots, scabs, viruses, and on with the sad list to end with wilts. It makes sense in an organizational way to end with the problems, but it makes for a sorry place to leave off.

This book is good on detailed info on soil micro-organisms and the general theme works globally. I recommend checking against local Extension Service or eOrganic before following any of the specific techniques, to ensure it’s likely to succeed where you live.

Growing Great Sweet Corn

Silver Queen sweet corn almost ready to harvest.
Photo Kathryn Simmons

I wrote about success with planting sweet corn in May. here are tips for continuing success as your corn grows!

Caring for the Sweet Corn Crop

Generally, corn needs cultivating (hoeing and weeding) at least twice, once two weeks after sowing, and once at four weeks. Even better are four cultivations: one at 7 days, a second at 14, a third around 21 days (when the plants are 6-12” (15-30cm) tall) and finally one around 35 days when they are 18-20” (45-50cm) high. We use a walk-behind tiller, and follow up with hoeing and thinning. A wheel hoe can be a useful tool. After about 30 days, corn plants get too big to get machinery between the rows.

Another good resource is ATTRA Sweet Corn: Organic Production.

At tight spacing, adequate irrigation becomes more important. Never allow soil in corn plantings to dry out. More than 1” (2.5cm) per week may be needed for maximum productivity, although corn is more drought tolerant than some crops. The most important times for watering are silking (when the silks first become visible outside the husks) and ear-filling.

There used to be a belief that it helped production to remove the suckers that came from the base of the plant. This idea has been tested, and that practice has been found to damage plants and possibly even reduce yields. (Reports from Clemson in 2002 and Colorado State in 2004).

Flame-weeding can be used after planting, pre-emergence, or, with care, after the crop is 2” (5cm) tall, using a directed flame. Consult ATTRA Flame Weeding for Vegetable Crops

Sweet corn undersown with soybeans as a cover crop. We often use soybeans as a traffic-tolerant, nitrogen-producing cover crop that also deters weeds.
Photo Kathryn Simmons

Undersowing Sweet Corn

No-till planting into strips tilled in a white clover living mulch sounds good but has been found tricky, especially during the grower’s learning curve. Jeanine Davis addresses this in NCSU’s Organic Sweet Corn Production. The clover may out-compete the corn, becoming invasive and hard to get rid of. Soil temperatures will be lower (a disadvantage in spring) and slugs and rodents may abound.

More successful is sowing a cover crop into the corn at the last cultivation, 28-35 days after emergence. We undersow with soybeans (oats and soybeans for our last planting). Although they don’t supply the highest amount of nitrogen, compared to other legumes, they are cheap, quick, somewhat shade tolerant and can withstand the foot traffic during harvesting. Other growers sow forage brassicas. Research has shown that this does not depress corn yields. The brassicas can be harvested for forage after the sweet corn harvest is finished. Undersowing with white clover is also possible.

Succession Planting of Sweet Corn

In order to have a continuous supply of sweet corn all summer, a bit of planning and record-keeping is called for so that each year’s plan can be fine-tuned. The easy and approximate method of getting a good supply is to sow more corn when the previous sowing has 3-4 leaves, or is 1-2” (2.5-5cm) tall. That will be about every two weeks. For a more even supply, sow several different varieties, with differing days to maturity, on the same date. We sow Bodacious (77 days), Kandy Korn (89 days) and Silver Queen (96 days) on the same day, and get over two weeks of harvests.

For fine-tuning for the most even supply, nothing beats real information about what happened, written at the time it happened. We have a Planting Schedule on a clipboard in the shed, and we write down actual sowing dates (next to the planned sowing date), and harvest start and finish dates. Having graphs of sowing and harvest dates for each crop has been very useful for planning effective planting dates. Use the Succession Planting method to calculate best planting dates and intervals for a continuous supply. We make six plantings: 4/26, 5/19, 6/6, 6/24, 7/7 and 7/16, to provide fresh eating every two weeks. The planting intervals are 23, 18, 18, 13, and 9 days. Because we plant three varieties, new corn comes in three times during each two weeks.

To calculate the last worthwhile sowing date, add the number of days to maturity and the length of the harvest window (7-14 days), and subtract this number from your average first frost date. For our 10/14 frost date, using an 80 day corn as an example, 80+7=87 days, brings us back to July 19 for our final sowing date. In practice, because corn matures faster in summer than in spring, this calculation gives you a little wiggle room in case the first frost is earlier than average. You could add a little more wiggle-room to be more sure. We make our last sowing on July 16.

Our sixth (and last) sweet corn planting showing our three-variety sequence. From the right: Bodacious, Kandy Korn and Silver Queen.
Photo Kathryn Simmons

Fast-Maturing Sweet Corn Varieties

Early Maturing Sh2 Varieties: The Supersweet corn varieties are where most of the attention goes these days, and bicolor is preferred. In order of maturity (speediness in ripening): Catalyst XR (bicolor, 66days); Sweetness synergistic (bicolor, 68d); Kickoff XR (bicolor, 69d); Temptress synergistic (bicolor, 70d); Xtra-Tender 2171 (bicolor, 71 d); Nicole (white, 72d); Xtra-tender 20173 (bicolor, 73d); Signature XR (bicolor, 73d); Anthem XR (bicolor, 74d); Natural Sweet Organic (bicolor, 74d); Xtra-tender  3473 (white, 75d); SS2742 (Bicolor, 75d)

Early Maturing SU Varieties: Among yellow SU cultivars, Earlivee is the earliest to mature, at 58 days, and Seneca Horizon matures in 65 days. Sugar Pearl at 73d  is the earliest white cultivar to mature. Quickie, at 64 days, Double Standard (OP, 73d) and Butter and Sugar at 73 d, are the earliest bicolor cultivars to mature.

Early Maturing SE Varieties: Among yellow SE varieties, Precocious and Spring Treat mature earliest, at 66 and 67 days, respectively. Bodacious (yellow, 75d) is well worth the wait! Of white varieties, Spring Snow, at 65 days, is the earliest to mature. There are no bicolor SE varieties.

Early maturing SE+ varieties: Sugar Buns (yellow, 70 days); Trinity (bicolor, 68d)

Remember, if you decide to grow several kinds, not to mix sh2 kinds with anything else, or everything will taste starchy.

Sweet Corn Season Extension

Transplanting can provide an earlier harvest, as already mentioned. Clear plastic mulch is sometimes used to increase soil temperature and germination rate, and to conserve moisture, producing earlier maturing corn. The plastic is spread over the seeded beds and slit when the seedlings emerge. It can be cut and removed 30 days after emergence. Weed-free seed beds are needed for this method to work organically, and plastics disposal is an issue. Rowcover is another way to warm soils (and keep birds off).

Our second sweet corn planting on July 8, a few weeks away from harvest.
Photo Pam Dawling

Pests and Diseases of Sweet Corn

Crows and other birds can be troublesome, removing the seed before it even grows. We leave the row-marking ropes in place (when hand sowing), or put some sticks and string in after machine sowing. Bird-scaring flash-tape may be even more effective. Rowcover would also work.

Some say interplanting corn with big vining squashes deters raccoons and other critters, but I think it deters crew too!

There are several caterpillar pests. An integrated organic approach to keeping pest numbers below economically damaging levels includes crop rotations, tillage, choosing resistant or tolerant varieties, encouraging beneficial insects, and ensuring adequate fertility and water. The next step is to scout for pests regularly, and take action as required.

Corn Ear Worm (CEW) is the most common pest. There may be six generations a year in the South. These caterpillars can bite – it’s just a nip, but can be a shock! A first line of defense is to choose varieties with tighter husks, which are harder for the worms to get into (Bodacious, Tuxedo, Silver Queen). Natural predators can be encouraged by planting alyssum or other small, open-flowered plants. You could buy Trichogramma wasps. The Zea-later was a tool developed for applying vegetable oil in the tip of each ear, mixed with Bt, 2-3 days past the full-brush stage of silking. Unfortunately  the treatment caused pollination problems and so it has fallen out of use. If pest numbers are not too high, you can simply cut or snap the ends off the ears.

Corn Earworm larvae come in many different colors. And they can bite!
(Photo: J. Obermeyer Purdue Extension)

European Corn Borer (ECB) drills through the whorl of leaves of the young plants, leaving a pattern of large holes as the plant develops. Bt and Spinosad will kill these, as will Trichogramma wasps. To reduce damage in future years, be sure to mow and disk old corn stalks into the soil at the first opportunity. Organically farmed soils have less of a problem with ECB.

Fall Army Worms (FAW) are also killed by Bt and Spinosad. These three pests (CEW, ECB, FAW) can be monitored in a single program, starting when the corn plants are at the whorl stage. At that point, scout for FAW, and treat if more than 15% of your plants are infested. At the pre-tassel and tassel stage scout for ECB and FAW. If infestation exceeds 15%, make a foliar spray with Bt or Spinosad. Check again in a week and repeat if needed. Then at the early silk stage, look for CEW and if needed, inject oil in the tips. If you also see ECB moths, apply Bt or Spinosad.

Cutworm can be a problem following sod, or if there are adjacent grassy areas. Bait them with bran, cornmeal or hardwood sawdust mixed with molasses and water – these baits swell inside the pests and kill them.

Corn Rootworms are best controlled by rigorous rotations.

For a more complete description of corn insect pests, see the 2004 Organic Insect Management in Sweet Corn by Ruth Hazzard & Pam Westgate. It includes good photos of the beasties. Cornell has a good Resource Guide for Organic Pest and Disease Management. Search under Crop Management Practices for Sweet Corn.  Be aware of the updated info on the pollination issues with applying oil in the ear tips, since these publications came out.

Corn Smut fungus (Ustilago maydis), known in Mexico as Huitlacoche, is edible at the stage when the galls are firm and tender. The flavor is sweetish. Silver Queen is the variety “best” at producing this fungus, should you wish to grow it. We carefully harvest the infected ears (or pieces of stem) into a special Smut Bucket, trying not to scatter the spores. Because none of us like this delicacy, we take it to the compost pile.

Young sweet corn plants in July (our fourth planting). And solar panels.
Photo Bridget Aleshire

Sweet Corn Harvest

Harvest corn before daybreak for best flavor, because the sugars manufactured in the plant the day before become concentrated during the night. We’re not that dedicated. We harvest ours in the morning, and hurry it to the walk-in cooler.

Harvest may start 18-24 days after half the ear silks show, if the weather has been reasonably warm. Judging corn’s ripeness is a skill, based on information from many of the senses. The first sign we look for is brown dead silks. If the ear has passed that test, we investigate further. All ears should look and feel plump and rounded to the tip. Each variety is a little different, so close attention is needed. Some varieties exhibit “flagging” of the ear, meaning it leans away from the stalk as it matures and gets heavier. New crew can test for ripeness by opening the side of the husk with thumb nails, and puncturing a kernel: the kernels should look filled-out and squarish, not round and pearly; the juice should be milky, not watery or doughy. The advantage of opening the side of the husks is that it is possible to close the gap if the ear is not ripe, without risk of collecting dew or rainfall. If the ear is ripe, we bend it downwards, give it a quarter-turn twist, and then pull up away from the plant.

We harvest every other day, which balances getting the amount we need with not spending more time than needed picking. Such a schedule can work well for CSA farms. Other growers could well need to harvest every day, if daily fresh corn is what your market needs. Leaving a three-day gap risks poor quality starchy ears and a lower total yield.

Take steps to keep the crop cool while harvesting. Never leave buckets of corn out in the sun. Even at room temperature, harvested OP ears lose half their sweetness in 24 hours.

After harvest, cool the corn quickly. Hydrocool if you have a large operation: drench or immerse the crop in near-freezing water. Otherwise, simply refrigerate and keep the corn cool until it reaches the consumer.

Some of this information comes from my book, Sustainable Market Farming.

Plentiful harvest of sweet corn and tomatoes.
Photo Twin Oaks Community

Dealing with weeds

 

Galinsoga- a fast-growing, fast-seeding weed of cultivated soil. Photo Wren Vile

Dealing with weeds

Why take action against weeds?

Weeds compete with crops for sunlight, water and nutrients, and can encourage fungal diseases by reducing airflow. Too-frequent cultivation to remove weeds can leave the soil more prone to erosion. Each tilling or deep hoeing stirs air into the soil and speeds combustion of organic matter. Most weeds respond well to nutrients, especially nitrogen. If you give corn too much nitrogen, even as compost, its productivity will max out and the weeds will use the remaining nutrients.

Remove weeds at their most vulnerable stage, or at the last minute before the seedpods explode —ignore weeds doing little damage.

Types of Weeds

  •   Annuals and perennials;
  • Stationary perennials (docks) and invasive perennials (Bermuda grass);
  • Cool-weather and warm-weather types;
  •  Quick-maturing and slow-maturing types;
  •   “Big Bang” types (pigweed) versus “Dribblers” (galinsoga).
Burdock is a large perennial weed with a huge root. Photo Bridget Aleshire

Sustainable Weed Management

1.      Prevent weeds from germinating

  •  Grow vigorous crops adapted to the locality,
  •  Switch between spring and summer crops in rotation,
  •  Mulch or tarp to bury short-lived weed seeds
  • Plant promptly after cultivation, so weeds don’t get the head start,
  • Transplant rather than direct sowing, giving your crop a head start on the weeds,
  • Use close spacings, leaving less space for weeds,
  • Use drip irrigation rather than sprinklers, discouraging weed germination between the rows,
  •  Plant cover crops, including no-till systems,
  • Reduce tillage whenever you can, for example, by relay planting, where the new crop is planted while the previous crop is still in place, and prevent new weed seeds coming up to the surface.
Remove weeds before they set seed. Thistle seeds blow a long way on the wind.
Photo Wren Vile

2.      Reduce weed seeding

  • Practice timely cultivation, mowing, flaming, grazing by cattle, chickens, ducks, geese. As Margaret Roach says: “No matter what weed you are facing, if it’s flowering or setting seed now, be sure to behead it: mow it down, harvest the blooms for bouquets, or otherwise prevent a successful sexual reproduction cycle.”
  • Reduce weed seed banks to 5% of original levels by preventing weeds from seeding for 5 consecutive years.
  •  Use post-emergence organic weed killers: corn gluten, vinegar, flaming
Dandelions are another perennial weed with seeds that blow and spread easily. Photo Wren Vile

3.      Reduce weed seed viability

  •  Reckon that most weed emergence happens within two years of the seeds being shed.
  •  Encourage seed-eating birds, insects, worms, mice
  •  Small, short-lived seeds of weeds with no dormancy period, such as galinsoga, will almost all die within a year or two if they are buried a few inches. Till and mulch to bury short-lived weed seeds.
  •  Longer-lived seeds (pigweed, lambsquarters, velvetleaf) if buried, may remain viable and dormant for years – Leave such weed seeds on the soil surface, rather than tilling them in! Delaying tillage if weeds have already seeded generally reduces the number of seeds added to the long-term seed bank. Seeds lying on or near the soil surface are more likely to deteriorate or become food for seed predators than buried seeds,
  •  If they do not get eaten, dry out or rot, seeds on top of the soil are more likely to germinate than buried seeds, and you can take prompt action.
  • Use stale seed-beds – prepare bed a couple of weeks before planting, water as if you had planted. The day before planting your crop, hoe the surface shallowly to kill new weeds,
  •  Solarize weedy soil in hot weather to kill weed seeds – mow the weeds, cover the soil tightly with clear plastic, weighted down or dug in round the edges. Bryan O’Hara in No-Till Intensive Vegetable Culture has popularized this technique, which makes a great use for used hoophouse plastic film. Solarizing can produce temperatures of 125˚F (50˚C) whereas temperatures under tarps (see section on perennial weeds) will be more like 110˚F (43˚C). You may need only 1-3 sunny days to kill crop residues with solarization. Cover crops and weeds may take longer to die. The heat will not go deep into the soil in that short time, and so more of the soil life will survive than with tarping.
Solarizing with clear plastic. Photo Pam Dawling

4.      Reduce the strength of perennial weed roots and rhizomes

  • Understand apical dominance: when a rhizome grows a green shoot, chemicals from that shoot prevent other nearby nodes on the same rhizome from sending up shoots.
  •  Act in a timely way – On long rhizomes, after a certain length, the dominance effect is too weak and another node can grow a shoot.
  •  Reduce the strength of perennial weed roots and rhizomes by frequent tilling or digging out.
  • Beware tilling invasive “traveling” perennial weeds once and thinking you’re done – When rhizomes are cut into pieces during tillage, the apical dominance is lost and each piece can grow a shoot of its own.
  •  Consider tarping: after tarping the plot for two summer weeks, 3-4 weeks in spring and fall, and two months or more in winter, dig out or pull up all the weed roots still alive.
  •  Next comes a counter-intuitive move (from Jesse Frost ): sow or transplant an intensive valuable crop in the areas with the worst perennial weed pressure. Of course this will motivate you to deal effectively with the weeds!
  • Pull out the pieces to dry on the surface – the depleted pieces of root or rhizome may die
  •  Or cultivate again when the new shoots have reduced the plant’s reserves (in the roots), but before they have grown enough to send energy back to the roots – it’s more effective than going almost daily after every sprig. Removing the shoots whenever the weeds reach the three- to four-leaf stage can be most effective.
  •  Late summer and fall turn out to be the best time for getting the upper hand over a wide range of common weeds, including Japanese knotweed, ragweed, Ailanthus, bindweed, curly dock and more. See Some weeds are best tackled late summer and fall Margaret Roach in A Way to Garden

Biointensive Integrated Pest Management

The weed strategies above follow the four steps of IPM: prevention, avoidance, monitoring and suppression.

1.      Prevention: Focus on restoring and enhancing natural balance and resilience to create healthy plants and soil, better able to withstand attacks. Maintain soil fertility, good drainage and soil structure; plant resistant, pest-tolerant, regionally adapted varieties; grow strong plants; practice good sanitation,

Hoe the small weeds in this bed of young lettuce soon, and the closing canopy of the lettuce will shade out most weeds after that. Photo Bridget Aleshire

2.      Avoidance: The next stage includes actions to reduce the chances of a weeds taking over. These actions are also known as physical controls. Physically remove weeds. Use good crop rotations, remove weed habitat, deter weeds. Provide habitat for weed seed predators.

3.      Monitoring:  regularly inspect your crops, find out when conditions are right for an outbreak of particular weeds. Be prepared. Identify your weeds and choose good strategies for each type. Decide when it is time to act. How to identify your weeds – online guides

4.      Suppression: When the prevention and avoidance strategies have been exhausted, control measures can be used to reduce damage of crops, while minimizing environmental risks. There are four types of sustainable bio-intensive control measures to choose from, starting with the least damaging to the wider environment:

  • a)      Biological control involves working to boost populations of existing resident weed seed predators. (For a few serious weed pests, like prickly pear, host-specific insect enemies are introduced)
  • b)      Microbial controls (bioherbicides) are plant-pathogenic fungi, bacteria, and viruses to kill weeds. Not common.
  • c)      Botanical control uses plant-based products for pest control. Examples include orange, clove and peppermint oils, and phytotoxic plant residues, such as root exudates from winter rye cover crops, and hay from sorghum, which inhibit germination of small seeds.
  • d)      Biorational controls (aka inorganic, mineral, controls) make use of manufactured products such as herbicidal soaps or strong vinegar.
Hoe weeds while they are small and you can be rid of those with short-lived seeds in a few years. Galinsoga and Outredgeous lettuce. Photo Pam Dawling

Critical weed-free period

One important factor is to observe the critical period of weed control for each crop. This is the period when crops are most affected by competition, whether from weeds, sister seedlings or those of an intercrop. Seedlings suffer more than transplants from being out-shaded. Transplants are soon past their critical weed-free period, perhaps half of it before you even set them out. As well as the critical period, take note of the severity of drop in yield for the particular crop. A lot of the information below comes from The Living Soil Handbook by Jesse Frost, which I had the pleasure of reviewing recently.

  • Small salad crops like arugula, spinach and baby lettuce mix, really need to be weed-free throughout their growth. Apart from the risk of being smothered and producing poorly, there is the risk of including bits of recognizable weeds in your salads.
  • Bulb onions also benefit from being weed-free throughout growth. Like other narrow-leaved plants, they are poor competitors. Carrots also are very poor competitors – for most of us, the over-abundance of carrot seedlings in the row are as much of a threat as the weeds. Parsnips are similar, with the added challenge that they are slow to emerge.
  • Peas do best with no competition, although, because they grow vertically, they can do OK with a companion crop such as spinach (or weeds!) a short distance away.
    Hilling potatoes before the weeds get too big will deal with the weeds as well as giving the potatoes more growing space. Photo Wren Vile

    Potatoes, weeds and standing water. Until the soil drains, the potatoes cannot be hilled, and the weeds here are already large. The yield will be reduced by weeds competing with the potatoes.  Photo Bridget Aleshire
  • Potatoes need 1-8 weeks after emergence free from weeds, although small weeds are not a problem and the process of hilling potatoes (needed to provide growing space) effectively deals with weeds.
  • Beets need 2-3 weeks after emergence weed-free from direct-sowing. My experience is that beets are their own worst enemy, and the clusters of seedlings that emerge from each seed-ball should be singled as soon as possible. Yields can easily drop 1-5% with small-average weeds. Turnips also need to be competition-free for the first few weeks after emergence.
  • Broccoli, cabbage, cauliflower, collards, kale and most Asian greens need 2-3 weeks after transplanting free of weeds.
  • Sweet potatoes need 2-6 weeks free of competition after planting. Because it gets hard to wade in and pull weeds later, we try to keep them weed-free.
Garlic beds under a stormy sky. Keep alliums free of weeds.
Photo Wren Vile
  • Garlic needs 3-7 weeks from emergence free of weeds. If you plant in the fall, start counting in early spring when weeds start to grow again. Like most alliums, the narrow vertical leaves make it a weak competitor.
  • Basil, cucumbers, squash, zucchini, lettuce and many other crops need four weeks from transplanting free of weeds. Be careful not to damage squash roots when removing weeds.
  •  Tomatoes need 5-6 weeks after transplanting free from competition, although they are fairly strong competitors later, and we routinely transplant our hoophouse tomatoes down the center of a bed of salad greens, progressively harvesting the greens over the next month. We have noticed problems only if we leave other crops too close for too long. Always prioritize the well-being of the new crop!
  • Peppers need 5-10 weeks after transplanting free from competition, although the drop in yield is small (5%)
  •  Fava beans need four weeks from emergence free of weeds
  •  Direct sown kale needs 6 weeks from emergence weed-free.
  • Okra requires 6-8 weeks after sowing weed-free. If you transplant okra as we do, half that period will be over by transplanting date.
  • Beans are a crop that can generally out-compete weeds (losing only 3% yield from competition), but keeping the rows clean until the beans flower (about 6 weeks from sowing) will maximize yields.
  • Corn needs about 7 weeks from seeding free of weeds (until there are 6 leaves).
  • Eggplant calls for 8 weeks from transplanting free of competition.
  •  Leeks, another weakly competitive allium, need 12 weeks post emergence weed-free. If, like us, you transplant leeks at about 10 weeks after sowing, this translates to hoeing the beds of transplanted leeks a couple of weeks of transplanting.

Flameweeding

I won’t say more about this here. Click the link to read previous posts.

Mulches

Mulches are a big asset in weed control. Organic mulches also add biomass to the soil. Remember not to use organic mulches around warm weather crops for their first month, as they need warm soil to grow well, and insulating mulches keep the soil cold.

See our experience with Biodegradable plastic mulch

Read Organic Farming Has A Plastic Problem. One Solution Is Controversial about the controversy surrounding biodegradable plastic in Organic Farming

Cover crops

Summer cover crops smother emerging weeds, prevent weed seed germination, between a spring food crop and a summer or fall one. Winter cover crops smother emerging winter annual weeds. Good cover crops for this purpose: sorghum-sudangrass, pearl millet, winter rye, wheat, barley, oats, buckwheat, brassicas (beware – rotation, bugs), lupins, red clover, subterranean clover, berseem clover, soybeans, cowpeas.

Ida Gold mustard (Sinapis alba) contains a gluscosinolate, ‘sinalbin’, a non-volatile compound that has shown the ability to inhibit weed seed germination. Tillage radish has a similar effect. The cover crop needs to be mowed and tilled in. Solarization after incorporating mustard is known as biofumigation.

Cover crops also improve the soil for crop production.

Iron and Clay southern peas as cover crop in the hoophouse, smothering weeds.
Photo Pam Dawling

Vegetable Garden Tips

 

Young Yukina Savoy plants.
Photo Ethan Hirsh

My virtual workshop on Asian Greens 

is available from Mother Earth News Fairs Online here.

The Food Independence Course Part Two  consists of eight video presentations, most of which come with pdf handouts. My contribution is Growing Asian Greens, and pairs nicely with the Guide to Asian Vegetables by Wendy Kiang-Spray, author of The Chinese Kitchen Garden: Growing Techniques and Family Recipes from a Classic Cuisine. Other topics include Dandelion Wine, Homemade Teas, Food Conversations, Passive Solar Greenhouse Design, Productive Growing from Home, and Growing Your Own Spices.

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Decoy Cabbage White Butterflies.
Photo Good Seed Co

Easy DIY Cabbage Butterfly Decoy!

The Good Seed Co blog posted this lovely idea for protecting brassicas from those white butterflies Pieris rapae. It’s based on the discovery that the butterfly is territorial. If it sees a slightly bigger competitor it flies away. I have not tested this system, but it sounds like an interesting and fun project that costs next to nothing.

http://goodseedco.net/blog/posts/cabbage-butterfly-decoy Posted 25th Jun, 2015 in On Our Mind by Robin Kelson

PageOfCabbageMoths_efile

Cut out paper decoy representations of the butterfly. Here’s a single page template you can download

We don’t have many cabbage butterflies  because we have both a predator – the paper wasp, and a parasite –  Cotesia glomerata, a parasitic wasp that lays its eggs in small (first instar) larvae of the Cabbage White Butterfly, or Imported Cabbage Worm (as we call it in the US). Cotesia larvae emerge from the caterpillars after 15-20 days and spin yellow or white cocoons on or near the host which dies when the wasps emerge. We often find clusters of these cocoons (about the size of cooked rice grains) on the underside of brassica leaves.

I learned from Bryan O’Hara in  No-Till Intensive Vegetable Culture that our friends, the Cotesia glomerata wasps that parasitize brassica caterpillars, and overwinter as pupal cocoons on the undersides of brassica leaves, will hatch out in spring on the very day the overwintered brassicas start to flower. The 20-50 day lifecycle needs brassica flowers, so don’t be in a hurry to cut down all your bolting greens! The flowers provide nectar for the adult wasps. The leaves, as we know, provide food for the caterpillars, which provide the host for the wasps to lay eggs in. The wasp larvae feed on the caterpillar until it dies, then pupate.

There’s an incredible National Geographic video of this cycle, showing parasitic wasp larvae swimming around inside a caterpillar, bursting out through its skin. The weirdest bit is that it is the dying caterpillar that spins the protective cocoons around the pupating larvae. And us who plant the brassicas that feed the caterpillars! Who is the farmer and who is farmed?

This video shows a paper wasp tackling a caterpillar.

This one shows Cotesia glomerata emerging

This one shows more about the parasitic Cotesia glomerata 


Savoy cabbage with frost. Savoys can take much colder temperatures than this!
Photo Lori Katz

Average First and Last Frost Dates

Harvest to Table has this helpful article:

Average First and Last Frost Dates for Cities, States, and Countries

Average frost dates – the last one in spring and the first one in the fall – are useful to know when planning your crops. Once you’ve calculated your planting out date for various crops, you can work back to set sowing dates for the crops you’ll transplant, and bed prep dates for every crop. You can also make a co-ordinated plan that paces the work and doesn’t have too much in any one week, or any while you plan to be on vacation. You can calculate your first sensible planting date for each crop, your last one and perhaps some in-between ones to keep up supplies throughout the season.

You can use your average first fall frost date to make sure you don’t plant frost-tender crops too late in the season when you have no hope of them maturing in time for a harvest. You can extrapolate beyond the frost date to figure out when to harvest the more hardy crops. See my Winter-Kill Temperatures chart for useful tips.

By looking at the number of frost-free days in your area you can see whether to grow long-season tender crops like watermelons, or whether it’s only worthwhile if you choose fast-maturing varieties.

The Harvest to Table website is a trove of clearly explained information.

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Soil thermometer with easy-to-spot backing in a bed of beets.
Photo Bridget Aleshire

Soil Temperatures

Average frosts are only averages. Actual frosts can sometimes happen two weeks either side of those dates. Frosts are only one particular temperature, and may not matter to the crop you’re planning for. Soil temperatures for germination and for planting are another important part of planning.

K-State Extension has a brief article on the importance of measuring your soil temperature.

The Empress of Dirt has a helpful list of Best Soil Temperatures for Sowing Vegetable Seeds, in alphabetical order by crop.

Harvest to Table also has a list, ranked by temperature, so you can see what you can plant this week.

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Scottish Climate Friendly Farming Video

Farmer Patrick Barbour, from Highland Perthshire, has won the search for Scotland’s climate friendly farming champion. Patrick’s innovative three-minute video entry, filmed at Mains of Fincastle, near Pitlochry stunningly illustrates the benefits of tree planting, species rich grassland, rotational grazing for cattle and sheep and stitching nitrogen fixing crops into pastures.  It is available to watch at: Next Generation Climate Change Competition

Patrick, Robert and Catherine Barbour of Mains of Fincastle, near Pitlochry
Photo The Scottish Farmer

Flame Weeding

Commiseration and sympathy to ice-blasted farmers and gardeners

Visits to my website shot up over the weekend. People are checking out my Winter-Kill Temperatures of Cold-Hardy Vegetables as they are dealing with temperatures considerably colder than they ever expected for their region.  I hope you can find some helpful information there while you triage your crops into “OK with these temperatures, can be left alone”/”might die, need help”/”will definitely die, no point in trying to save them”.

Q and A

Next a couple of questions that people left on the contact form, that I thought others might be interested in.

Q1. Is there an easy way to figure out what vegetables I can plant to maximize my space and yield. I am not sure if its my soil or sunlight availability in my backyard garden.

A. Most vegetables do need at least 6 hours a day of sunlight, so as we get closer to spring, assess various spots in your backyard. Maximizing use of the space includes careful choice of plant spacing, but also following one crop with another, or squeezing crops in between others. There’s no quick answer. Search my site for Succession Planting, Crop Spacing, Choosing Crops.

Q2. I am currently looking for Onion seeds or seedlings to purchase for approximately 1hector to plant. We based in the Free State Area.

A. South Africa? Sorry, I have no idea what is available where you are. 1 hectare is a huge area for onions, especially if you have never grown them before. Use transplants, not direct-seeded onions. Choose varieties adapted to your latitude, or else they may never grow big, or may not dry down and store well.

Flaming can be used for weed control, pest control, or crop termination.

Flame weeding can be used for carrots and beets before emergence.
Photo Brittany Lewis

Our introduction to flame-weeding was via the first article I ever read in Growing for Market magazine. It was about flaming for pre-emergence weed control in carrots. It sounded like such an effective method that we bought a Red Dragon flamer and never looked back! I remember saying and writing that it worked so well it felt like cheating!

Our flamer

We use a handheld flamer attached to a propane cylinder that is in a wheelbarrow pushed by a second person behind the first. This person also acts as a “fire warden.” Some growers mount the propane on a backpack frame. Walking along the aisle between beds and wafting the wand diagonally back and forth across the bed takes about ten minutes for a 100′ (30 m) bed. Flame-weeding alone can reduce hand-weeding to one hour/100′ (30 m). Hand-weeding can be reduced to 6 minutes/100′ (30 m) by flame-weeding after using stale beds which have been hoed three or four times.

Stale seedbed flaming for weed control

In the stale seedbed technique, the bed is prepared and watered ahead of planting time and one or more flushes of weeds are germinated and flamed or hoed off. Flaming avoids bringing any new weed seeds to the surface. To sow large crop seeds into a seedbed that has already had the weeds removed (by flaming or other stale seedbed technique), you can use a stick seeder or easy-plant jab planter. Making furrows for small seeds will inevitably activate a few weed seeds along the rows.

Flame weeding, pre-emergence

Flame weeding a carrot bed.
Photo Kati Falger

Carrots, beets and parsnips are ideal crops for pre-emergence flame-weeding. They do very poorly with competition, and grow more slowly than weeds, consuming lots of time hoeing, cultivating and hand weeding to get good yields. Flame weeding can change all that, with pre-emergence either as part of a stale seedbed technique, or post-sowing.

The latter method is to prepare the bed, sow the seeds, water, and then monitor carefully. The day before you expect the carrots to emerge, flame across the whole surface of the bed. Use a soil thermometer and the table here to figure out which day to flame.

Table of vegetable seed germination as a function of soil temperature

 

Days to Germinate 50F (10C) 59F (15C) 68F (20C) 77F (25C) 86F (30C) 95F (35C)
Carrots 17.3 10.1 6.9 6.2 6.0 8.6
Beets 16.7 9.7 6.2 5.0 4.5 4.6
We sow “indicator beets” with our carrots so that we know when to flame-weed them
Photo Kathryn Simmons

People who use pre-emergence flame-weeding for carrots can use a few “indicator beet” seeds sown at one end of the bed to show when to flame. As soon as you see the red loops of the beet seedlings breaking the surface, flame the carrots. (But look for carrots too, just in case!) Beets are always a bit quicker than carrots in germinating. Note that beets are about half a day ahead of carrots at 50°F–68°F (10°C–20°C), but more than a day at 77°F–95°F (25°C–35°C). The challenge with carrots is to keep the soil surface damp until they come through. As an indicator for beet seeds, you can use a few radish seeds.

Another way to get an alarm call is to put a piece of glass over part of a row. The theory is that the soil under the glass will be warmer and the crop there will come up sooner than the rest. I tried this once, but the soil under the glass dried out, and those carrots came up later than the rest! Nowadays we have a “no glass in the garden” rule, for safety, so I use beets, the thermometer and the chart.

See the useful resource Flame Weeding for Vegetable Crops  from ATTRA

Flame-weeding growing crops

Potatoes can get impossible to hill when you’d like to if you have wet weather, and this is where flaming can save the day. Potatoes may be flamed at 6″–12″ (15–30 cm) tall, to kill weeds without damaging the potato plants. After that, flaming is not recommended.

Sweet corn can be flame-weeded after planting, either pre-emergence or, with care, after the crop is two inches (5 cm) tall, using a directed flame.

Onion and garlic crops can be flame-weeded when relatively mature. Flame-weeding can achieve as good results as hand-weeding using one-third of the labor. Flame-weeding can damage young plants (four or fewer leaves), so bide your time. Direct the flame at the base of the plants, in the morning, when the plants are turgid. This technique is for unmulched crops. Naturally, if you have used straw or hay mulch, flame-weeding is not such a smart idea!

Peanut seedlings can be slow to emerge, so pre-emergence flame-weeding may be helpful. The seedlings look somewhat like peas or clover. Because they grow slowly for the first 40 days, they will not thrive if you lose them in weeds (guess how I know?!).

Flaming for ending potato growth

Potato plants come to a natural end when the leaves die, after which no further growth can be induced in them. Once the tops die, the potato skins start to toughen up. If you are growing storage potatoes and are impatient for the end to come, you can mow off the tops or flame them, to start the skin-thickening process, which takes around two weeks. The potatoes are ready when you can rub two together without any obvious damage to the skins.

Flaming for pest control

Pest habitat includes all those half-wild edges and odd corners. You can reduce the pest count in these havens by mowing, hand weeding, or flaming. Be sure not to remove all the habitat for beneficial insects while you do this.

Colorado Potato beetle late stage larva
Photo Pam Dawling

Colorado potato beetles can be tackled by flaming while the potatoes are less than eight inches (20 cm) tall, as an effective pest control measure. It won’t kill the potato plants. Choose a warm sunny day when the pests are at the top of the plants. Flaming can kill 90 percent of the adults and 30 percent of the egg masses, according to ATTRA.

Harvesting from bean plants with bad bean beetle damage.
Photo Wren Vile

Mexican bean beetles can be killed by flaming after harvest for that planting is finished. Flaming will kill the plants too. We used to plant six or seven successions of beans, every two weeks, then flame the old plants when the pest count got too high, and move on to a newer planting. Nowadays we buy the Pediobius parasitic wasp to deal with the MBB, and we can sow beans less often and harvest them for longer.

Flaming trap crops

Young turnips (with flea beetles!) in need of thinning for cooking greens.
Photo Pam Dawling

Flea beetles can be lured by a row of mustard greens. They like the pungent compounds in brassicas. Once you have lured the flea beetles you need to deal with them before you create a flea beetle breeding ground. Flaming the mustard plants is one possibility.

Striped cucumber beetle in squash flower. Photo Pam Dawling

Cucumber beetles  have a preference for some particular squash varieties, which may be grown as a trap crop: Cocozelle summer squash, Seneca and Dark Green zucchini are all “cucumber beetle preferred”! When beetles accumulate in the trap crop, flame it or till it in.

Stink bugs: Russ Mizell has published a paper on trap cropping for native stink bugs in the South. He recommends buckwheat, triticale, sunflower, millet, field pea and sorghum. A succession of trap crops including these and others such as pumpkins, cowpeas and other small grains (which are most attractive in the milk or soft dough stage) could help. Flame the trap crops when the stink bug numbers in the trap crop build up.

Excerpted and adapted from Sustainable Market Farming

Repurposed stroller makes a fine flame weeder.
Photo Sustainable Harvest Farm Kentucky

Root Crops in October

Radish Quick Pickles
Photo by Bridget Aleshire

Root Crops to Plant in Central Virginia in October

We have now passed our last chances to sow root crops outdoors. But the exciting season in the hoophouse has just begun. In early October, we sow radishes in our hoophouse. See Root Crops in September for more about our succession of hoophouse radish sowing dates. We like Easter Egg (a multi-colored mix of red, plum, pink, purple and white varieties, that matures over several weeks), Cherry Belle, the fast, uniform red globes, and White Icicle, like baby daikon about 3” (7 cm) long. These three varieties all stay crunchy and tender. We have a dread of fibrous radishes! Most years we make a sowing at the beginning of October and another at the end, and these will feed us from early November until early February. The late October sowing lasts for 8 weeks, so it’s good to make sure we plant enough. Radishes do a lot to brighten up meals in December and January!

White Egg Turnips.
Photo Southern Exposure Seed Exchange

In mid-October (10/10-10/25), we sow our first of three plantings of hoophouse turnips. We like the very fast-growing and tender Hakurei hybrid. It has short hairless tops which also make good eating. We sow this variety on the south side of the bed, leaving the other 3 rows for the taller varieties. We also like Early White Egg and Oasis, which are not quite as uniform as Hakurei, but are OPs and the seed is much cheaper. They produce more greens, which we value too. In the north row we often grow Red Round, a beautiful red-skinned turnip with tall attractive leaves. We also like Scarlet Ohno Revival, which has the advantage of hairless leaves. This is an Open Source Seed Initiative variety. The OSSI pledge: “You have the freedom to use these OSSI-Pledged seeds in any way you choose. In return, you pledge not to restrict others’ use of these seeds or their derivatives by patents or other means, and to include this pledge with any transfer of these seeds or their derivatives.”.

We thin the turnips as needed. If we sowed thickly, the first thinnings become baby greens for salad. Once the turnips are the size of marbles, we like to thin the plants to 3” (7 cm) apart and cook them whole, roots and greens together. The next thinning is to 6” (15 cm) and from that point on, we harvest the greens and roots separately. We get a ratio of one bucket of roots to two buckets of greens, which fits our needs perfectly. We like to mix the roots, as the one quarter of red roots adds a pop to the appearance.

Root Crops to Harvest in Central Virginia in October

Misato Rose Winter Radish.
Photo Southern Exposure Seed Exchange

We can continue harvesting beets (and beet greens), carrots, horseradish, kohlrabi, radishes, turnips (and turnip greens), and winter radishes outdoors. Once we have had a decisive frost we can harvest parsnips – the frost really improves the flavor. Our 9/6 sowing of hoophouse radishes will start to mature.

See Washing, sorting and storing root crops in Root Crops in September

We tackle our process of clearing root crops and storing them, starting with celeriac (if we grew it this year). We start with the least cold tolerant roots and work our way to the most cold tolerant. This list is root crops only. See my list of Winter-Kill Temperatures of Cold-Hardy Winter Vegetables 2020 for a more complete picture of “Harvesting in Time”

Clear and store (in this order):

  • Sweet potatoes 50°F (10°C)
  • “White” Peruvian potatoes 32°F (0°C) approximately
  • Celeriac 20°F (°C)
  • Turnips 20°F (°C)
  • Winter radish 20°F (°C)
  • Beets 15-20°F (°C)
  • Kohlrabi, 15°F (°C)
  • Carrots 12° F (°C)
  • Parsnips 0°F (°C)
Bucket lid with holes for sorting root vegetables for storage.
Photo Wren Vile
  • Wash, and store roots in perforated plastic bags in refrigerator or root cellar. We use a special measuring bucket lid to help new workers determine if roots are big enough to store.
  • Harvest sweet potatoes before soil temperatures go much below 55°F (13°C), or night air goes below 50°F (10°C). See the Special Topic below.
  • Harvest white potatoes when the skins have thickened. (When the skin is undamaged after rubbing two together. About 2 weeks after the  tops die). See Harvesting Potatoes and Root Crops in June. Two or three days before harvesting, we spend the day removing the hay mulch from our 1600 row feet (488 m) potato patch to the compost area. Our potato digging machine can’t deal with mulch or heavy weeds. To fit with using machinery, we clear complete rows. We have a Perfect Potato Harvest Checklist. For fall harvesting we do the tractor work in the morning and pick up the potatoes in the afternoon, avoiding leaving any out overnight if it will be frosty. (When harvesting the March-planted potatoes in July, we do the tractor work early in the morning and start picking up the potatoes as soon as possible. We aim not to be outdoors after lunch when it’s hot, but if we need to, we will, as we don’t want ready-baked potatoes sitting on the soil!) Tractor time is 4 hrs x 2 people. Picking time is 30 people-hours.
  • For beets, we allow 6 people-hours per bed (360 row feet (110 m), and expect 2-3 50-pound (23 k) bags per bed. Cut the stems about ¼” (6 mm) above the root, to reduce “bleeding” when you cook the beets. I was reminded recently that not everyone knows that the easiest way to cook beets is to scrub them, boil them in the skins, drain and immerse in cold water, then simply slide the skins off. Hardly any wasted food and no wasted time.
  • Bucket of freshly harvested Detroit Dark Red beets for storage.
    Photo Pam Dawling
  • For carrots, we allow 4.5-6.5 people-hours per (large) garden cart for washing, trimming and sorting. Plan to keep the last 15 minutes for clean-up. Divide the rest of the time available by 3. Use 1/3 of the time for digging, 2/3 of the time for washing and sorting. Add time to take to storage. Record yields. We take the carrot tops back and spread them across the beds. (fall harvest only ). In the spring and summer we take carrot tops to the compost pile, as the smell can attract carrot rust root flies. In late fall it is too late to sow cover crops to protect the soil, and the flies have gone to overwinter wherever they do that, so we spread the tops over the beds to provide some protection for the soil.)
Carrot rust fly damage (or possibly carrot weevil) Photo Jessie Doyle
Carrot pest larvae: carrot rust fly I think. Maybe carrot weevil.
Photo Jessie Doyle

Special Root Crop Topic for October in Central Virginia:

Harvest sweet potatoes

Here’s our method:

First roll up the drip tape. Harvest on 3 mild days – generally in the week that your first frost usually occurs (10/7-14). We expect our whole harvest of 800 row feet (244 m) to take 80 people hours. Allow 1/3 of the time for snipping, 1/3 for digging, 1/3 for crating and schlepping. Digging takes a bit less time than either of the other jobs. Even a few hours exposed to temperatures below 50°F (10°C) will cause chilling injury. (Frost on the leaves does not of itself damage the roots). Don’t leave clipped plants uncovered overnight. Don’t leave sweet potatoes outdoors. Clip the vines, dig carefully, set the tubers in plant-clusters to dry on the soil. Select seed tubers (healthy med-size tubers from high-yielding plants, no rat-tails).  We save a generous 100 Georgia Jet, 100 Beauregard, 20 each of Bill Shane’s White and Jubilee. (These last two are unofficial names for varieties we were given and are maintaining for genetic diversity.)

Sweet potato harvest.
Photo Nina Gentle

Other Root Crop Tasks in Central Virginia in October:

Curing sweet potatoes and white potatoes

Cure sweet potatoes in collapsible, stackable holey crates (or in wooden flats with spacers for ventilation) and cover with newspaper on top, in a basement with the heater on, for 10-14 days (85-90°F, 27-32°C, 80-90% humidity) or longer if it’s cooler and drier.  Use fans. Splash water on floor. Curing is complete when the skin is undamaged after rubbing two together. Restack the boxes (in a rodent-proof storage cage, if you are using an outbuilding).

Cure freshly harvested white potatoes in a root cellar at 60-75°F (15.5-24°C) for 2 weeks, with good ventilation, then cool cellar to lower temperature. See Special Topic for July. For weeks 2-4, the temperature goal is 50°F (10°C), and fresh air is needed about once a week. Our method of providing an air change in our cellar or adjusting the temperature is to leave the door open when the temperature will be closer to our goal than the current reality. It works well enough.

Growing High-Yielding Sweet Potatoes

Healthy sweet potato plants. A few insect bites won’t hurt!
Photo Kathryn Simmons

Growing High-Yielding Sweet Potatoes

In May I gave information on planting sweet potatoes. Hopefully that went well for you, and by now you have a large patch of healthy green vines. Let’s keep it that way! Here I will tell you about what the growing plants need, and the pests, disease and afflictions to avoid.

Read more

I have a Sweet Potato slideshow. I have lot of other posts on sweet potatoes (mostly about propagating our own slips, or about harvesting). Click to see the links in last month’s post

The ATTRA publication Sweetpotato: Organic Production is a good introduction.

Oklahoma State University Extension Sweet Potato Production is a clear concise publication (although it’s not organic).

Sweet potato development

This paragraph was included in Planting Sweet Potatoes, and I’m repeating it here, as a good reality check on what you can expect.

Regardless of how early in the season you plant them out, they will not make flowers earlier, or start making tubers sooner. Both flower and tuber initiation are triggered by day length. Each variety has its own internal clock. Most varieties take 90–110 days from planting out to reach a good size, if the weather is warm enough.

The first month or so after transplanting is the root development stage. Roots can go 8’ (2.4 m) deep in 40 days. Don’t be alarmed at the lack of above-ground action. The second month or so is the vine growth stage. The roots begin to store starch and sugar close to the stem base. During the last month of growth for that variety (3rd or 4th month), the potatoes develop. Make sure you dig them up before the soil temperature gets down to 55˚F (13˚C) – the week of the average first fall frost is about right.

Growing sweet potatoes – Three Ws: water, warmth, weed-free
  1. Water
  • The critical time to maintain sufficient moisture is after transplanting for at least the first 20-40 days while roots are developing. By now, most growers will be beyond this most-important watering period. But if it’s less than 40 days since you planted them out, keep the soil moist. Use your fingers to test the soil for dampness.
  • Once they are established, sweet potato plants are fairly drought-tolerant. But if you want high yields, they’ll need water once a week, either from the sky, or provided by you. Note that if you are using plastic mulch, rain won’t go through it, so I hope you installed drip irrigation below the plastic. If not, lay it on top, right beside the plants. Aim to provide an inch (2.5 cm) of water per week.
  1. Warmth
  • Sweet potatoes need warmth! Heat determines success; the number of days from planting does not.
  • Provided the weather is warm enough, most varieties take 90–110 days from planting out to reach a good size.
  • You can gain warmth in a cold climate, by planting inside a hoophouse or low tunnel covered in clear plastic. Ventilate in hot weather.
  • Growing Degree Days (heat units) are a tool for measuring accumulated heat, but you don’t need to calculate GDDs to get a good crop!
  • Early varieties take 1200 GDDs to grow a good crop.
  • To calculate GDDs, take the day’s high temperature (max) and the day’s low temperature (min) and add them together. Divide by 2 and subtract the base temperature of 55F. (Apologies to the rest of the world – I only know this method using Fahrenheit, but I’m sure you can find out how to do the calculations in Celsius). There are phone apps that will do the calculation for you.
  • Example: For a daytime max of 90F, and a night-time min of 70F, you get 25 GDDs – just about perfect for sweet potatoes. 90+70=160. 160/2=80. 80-55=25. At 25 GDDs a day, you theoretically only need about 48 days to get a crop. There are some other limits to daily plant growth – the likely minimum for a decent crop is about 76 days.
  • In a plastic tunnel, you can get 20 GDDs a day or more, rather than the 5 you might get outdoors.

    Water, warmth and no weeds – all that growing sweet potatoes need.
    Photo Nina Gentle
  1. Weed-free
  • Cultivate to remove weeds until the vines cover the ground, after which very little weeding will be needed.
  • If you have plastic mulch, walk through pulling weeds, and drop them on the plastic to cook. If you are growing on bare soil, hoe while the weeds are small, and pull if the weeds and the vines get ahead of you.
  • Weeding is generally not onerous because the sweet potato vines cover the ground within 6 weeks of planting and smother any newly emerging weeds.
Our motion sensor sprinkler and the outer layer of our fence around the sweet potato patch at the end of May.
Photo Pam Dawling
Solar electric fence controller for our sweet potato patch.
Photo Wren Vile
Pest mammals
  • Deer eat sweet potato plants at all stages, including digging out the roots in the fall. Dogs, fences and guns are the three most effective methods of deer control. The plants can be covered with row cover or plastic net for the growing season. Motion-sensor sprayers work well if maintained.
  • Rabbits eat the foliage. Plant the slips on black plastic to hold back weeds, then put wire hoops over the rows and cover with row cover for 3–4 weeks while the plants are young. Even after the plants are large rabbits can cause substantial losses.
  • Groundhogs dig and eat the roots. They can be trapped with baits of fruit. What’s for dinner?
  • Pocket Gophers search out sweet potatoes to eat. Their mounds may be hidden under the foliage and the plants may survive as they only eat the larger roots, leaving no crop.
  • Voles move in from grassy areas to live under the mulch and feed as fast as the roots form. They eat the roots from the top down leaving the outer shell in the soil where they have feasted. Cats are the best control.
  • Rats love the roots. Cats or dogs are the best methods of control.
  • Field Mice build nests under black plastic and eat the roots emerging from the ground.
Why not eat some sweet potato leaves as summer greens?
Photo Nina Gentle
Human “pests” of sweet potatoes

 You can eat sweet potato leaves yourself and it takes several meals to reduce yields of the tubers. Some researchers working in Vietnam, discovered that harvesting 25%, 50%, 75% or 100% of the vines every 15, 20, or 30 days (ignoring the information about the season of the year and the varieties) gave the sort of results you might expect. Harvesting tops every 20 days gave highest yields of greens. Harvesting 50% of the greens each time gave highest total yields of greens. Harvesting not more than 25% or 50% of the greens each time gave the highest eventual tuber yields, after 120 days. Researchers in Tanzania came up with the clear information that harvesting three times at one month intervals gave the highest greens production, but the tuber yield was affected tremendously. Harvesting tops twice in a growing period proved the best in leaf production as well as root yields. So, clip 25-50% of the tops of each plant up to twice in one summer, and you’ll still get a good yield of roots.

Also see the University of Arkansas Extension Nutritional and Medicinal Qualities of Sweetpotato Tops and Leaves. This publication explains how to plant slips 2” (5 cm) apart, specifically for greens (vine tips) and harvest 6 times between the end of April and the end of October.

 Insect pests of sweet potatoes

See North Carolina State University, Pests of Sweetpotato  for photos, drawings and details.

Although there are many insect pests that feed on sweet potato vines and leaves, most do very little damage, and hunting them down is not justified.

Healthy sweet potato patch, with some deer nibbling and weeds..
Photo Wren Vile
Pests that feed on foliage
  • Sweet potato flea beetles – Tiny black/bronze oval beetles (1.6 mm long), with reddish-yellow legs, and ridged wing covers; make small shot-holes in leaves or grooves in the upper surface of the leaves. Damaged areas turn brown and die. See below about larvae.
  • Sweet potato weevil adults and larvae do feed on the foliage, but mostly go for the roots (see below).
  • Caterpillars of three kinds:
    • Southern armyworms – Gray-black larvae up to 36 mm long with green or pink tints; pale longitudinal stripes and pairs of triangular spots along the back; pale yellow heads with bright red-brown marks. They feed on leaves and tips of vines, and congregate around the bases of plants during the middle of the day.
    • Sweet potato hornworms – First instar: white with a black horn; later instars (up to 90 mm long): green or brown with black diagonal lines down each side and a black horn, with a green or brown head with black stripes. They defoliate plants and often hide under leaves near the bases of plants.
    • Yellow-striped armyworms – Pale gray-black caterpillars up to 45 mm long, with orange-yellow stripes along the sides and pairs of triangular spots on the back of most segments; brown heads with black markings and a white inverted V. They feed similarly to southern armyworms.
  • Potato leafhoppers – Wedge-shaped insects up to 3 mm long; green bodies with yellow to dark green spots. They usually jump rather than fly. They suck sap from the underside of leaves causing yellowing of leaf tips and margins.
  • Fruit or vinegar flies – Small yellowish red-eyed flies about 3 mm long. They hover around overripe or decaying produce. They may be found with their small creamy maggots in cracks in sweet potatoes.
  • Tortoise beetle adults and larvae – Long-oval shaped gold beetles, up to 8 mm long, with various black or red markings on their flattened, shell-like bodies. The larvae have dull yellow, brown, or green bodies up to 12 mm long and black heads, legs, spots, and spines. Long spines on the abdomen hold excrement. Adults and larvae chew the leaves riddling them with holes.
  • Spider mites – Tiny reddish or pale spider-like arthropods that feed on the underside of leaves. Heavily infested plants develop a yellowish, bronzed or burned appearance.
Pests that feed underground on tubers and side roots
  • Sweet potato flea beetle larvae – Thin white, cylindrical larvae, up to 5 mm long, with 3 pairs of legs near their heads. They make shallow, winding tunnels on the surface of sweet potato roots and sweet potatoes. The tunnels darken, split, and leave scars.
  • Sweet potato weevil adults and larvae –Snouted beetles 6 mm long with dark-blue wing cases, orange-red legs and thorax, and fat, legless, 9 mm grubby white larvae with pale brown heads. The beetles make small holes over the surface of sweet potatoes mostly at the stem end. The larvae tunnel inside the tubers, leaving frass, which causes the sweet potatoes to taste bitter.
  • White grubs (spring rose beetles) – Dirty white grubs up to 25 mm long with brown heads and 3 pairs of legs near their heads. They leave large, shallow feeding scars on the sweet potatoes.
  • Wireworms – Thin, tough, wire-like larvae with 3 pairs of short legs near their heads and prolegs at the end of the body. They initially create large shallow cavities in sweet potatoes which they later excavate into deep ragged holes. Three species, with colors from yellowish-brown to cream or yellow-grey. Heads are darker, brownish.
  • White-fringed beetle larvae – Yellow-white legless, 12-segmented grubs, up to 13 mm in length, with small, pale heads. They chew into the roots.
Sweet potato souring.
Photo North Carolina Sweet Potato Commission
Afflictions of sweet potatoes (these are not caused by disease organisms) 
  • Round chunky roots, low yield, purple color: Planted too early, too cold.
  • Low yield: Flooded or crusted soil 6-7 weeks after planting? Planted too early?
  • Rough irregular shaped roots: Heavy clay soils or organic matter above 2%.
  • Rattails – thin, tough, tubers: Hot dry weather, insufficient water.
  • Long, slender malformed roots, reduced yield: Potassium deficiency.
  • Souring – Tissue breakdown caused by poor soil aeration, such as flooding.
  • Water blisters – Small whitish bumps around the lenticels (breathing holes): wet soil.
  • Blister – Small raised bumps appearing several months into storage: boron deficiency.
  • Fine hairline cracks: Another sign of boron deficiency.
  • Cracking: Uneven water supply or too much late-season water.
Sweet potato Ring Rot.
Photo North Carolina Sweet Potato Commission
Sweet potato feathery mottle virus.
Photo North Carolina Sweet Potato Commission
Diseases of sweet potatoes (mostly fungal)

 More info and photos: North Carolina State University Diseases of Sweetpotatoes. 

  • Brownish skin patches, worse in wet years: Scurf fungus, Monilochaetes infuscans. More likely if too much compost was used. Stored roots shrivel.
  • Metallic black surface lesions, maybe covering most of the root: black rot fungus, Certocystis fimbriata. Internal decay is not deep, but the fungus may impart a bitter flavor.
  • Sunken brown lesions that may completely encircle the root: ring rot, Pythium
  • Sunken lesions that dry and may fall out: Circular Spot, Sclerotium rolfsii. May taste bitter.
  • Hard, dry, black, sunken spots developing in harvest wounds: Fusarium. Spots may become larger than 2″ (5 cm) diameter, but damage is not deep.
  • Pitting: Soil rot or soil pox fungus in the presence of water stress. Roots will be small and malformed.
  • Streptomyces root rot bacterium causes a similar rot.
  • Fine or coarse irregular cracks, browning of the surface; dry, corky, dark-colored clumps of tissue scattered throughout the flesh, becoming worse if roots are stored warmer than 60°F (16°C): russet-crack/internal cork, feathery mottle virus (yellow feathery patterns of leaves). Do not use as seed stock.
When to harvest sweet potatoes

Unlike white potatoes, which have the annual plant sequence of vegetative growth, flowering and dying back, sweet potato plants would go on growing forever if the weather remained warm enough. Choose when to dig them up, ahead of cold weather. The longer you wait, the bigger the potatoes, but you are gambling with the weather. Usually sweet potatoes are harvested in the week that the first frost typically occurs in your region. I have written plenty already in previous years about harvesting, so I won’t go into it here. See one of the links to those posts, or my slideshow, if you want to know what comes next, or your climate is considerably colder than mine in central Virginia.

Our sweet potatoes next to our sixth sweet corn planting.
Photo Ezra Freeman

Potato pests and diseases

Potato pests and diseases

These potatoes were almost killed by frost two weeks previously, and have now recovered.
Photo Pam Dawling

This is part of a monthly series on growing potatoes, a dietary staple.

PART ONE: Planting potatoes (April)

PART TWO: Growing potatoes (May)

PART THREE: Potato pests and diseases (this one, June)

PART FOUR: Harvesting potatoes (July)

PART FIVE: Storing potatoes (August)

PART SIX: Planning to grow potatoes again (September)

I have a whole chapter about potatoes in Sustainable Market Farming, where most of this information can be found.

See Root Crops in June for info on digging up new potatoes, if you can’t wait for them to mature!

See The Potato Association of America, Commercial Potato Production in North America 2010 for lots of interesting info, including planting in hot weather. (But hurry up, you need to have enough growing days left in the season to get them to maturity.)

Organic Integrated Pest Management involves tackling pest problems one step at a time with ecologically-based practices, starting with actions to reduce the chances of the pest ever getting a grip on your crops. I recommend the ATTRA online publication Organic Integrated Pest Management. Each of the 22 pages is a poster, complete with good photos and concise clear info. Because nightshades have a lot of fungal, bacterial and viral diseases, it pays to take action to minimize the chance of diseases attacking your plants.

June-planted potatoes in early September
Photo Kathryn Simmons

Integrated Pest Management in Organic Field Crops Webinar from eOrganic

https://www.youtube.com/watch?v=nQXC8SElTMk

Biological IPM disease and pest reduction strategies for potatoes

  1. Cultivate strong crops and provide healthy soil, sufficient space, nutrients and water, suitable temperature, and soil pH.
  • Choose varieties that resist the pests and diseases you most expect. Improve the soil tilth, drainage and aeration. Chisel plow or broadfork to break hardpan, or grow deep-rooting cover crops ahead of your potatoes. Maximize air circulation around the plants. Choose a bright, breezy location (avoid frost pockets as they also collect dew), orient the rows parallel to prevailing winds and give the plants plenty of space.
  • Add compost and cover crops to build fertile soil to support strong plant growth and help increase the diversity of soil microorganisms, building naturally disease-suppressing soil. Use foliar sprays of seaweed extract, microbial inoculants or compost tea to boost general disease resistance. Consult ATTRA for compost tea Brew one part of compost to 5 parts water by volume for 14 days before spraying.
  • Practice crop rotation to reduce the chances of pests and diseases carrying over from one crop to the next. For potatoes, it’s best to rotate away from nightshade crops for at least three years. We don’t manage this ideal of one year in four. In our ten-year rotation, three of our ten years are nightshades (one paste tomatoes and peppers, two plantings of potatoes).
  • Practice good sanitation. Clear old crops promptly, so they don’t act as a breeding ground for pests or diseases. Avoid smoking, especially near nightshades, and have smokers wash their hands with soap or milk before working with potatoes. Tobacco can spread tobacco mosaic virus (TMV) to nightshade plants. Avoid working potato plants while the leaves are wet. Remove and destroy diseased plants, especially for late blight. Clean tools in between use in one field and another. When the harvest is finished, till the tops into the soil to speed decomposition, or remove and compost or burn them if growing on a small scale.
  • Remove nightshade weeds (e.g., horsenettle, jimsonweed and black nightshade), which can be alternate hosts for pests and diseases.
Potatoes, weeds and standing water. Don’t let this happen to you! Provide good drainage, remove weeds especially nightshade weeds.
Photo Bridget Aleshire
  • Prevent soil splash-back onto leaves, to reduce outbreaks of soil-borne diseases. Use drip irrigation rather than overhead sprinklers.
July photo of a mulched June-planted potato.
Photo Wren Vile
  1. Cover or protect the plants physically from the pests
    • mulches to stop soil-dwelling pests (CPB) moving up into your crops
    • netting or rowcover to protect from airborne pests (leaf hoppers, blister beetles)
  2. Provide habitat for natural enemies and other beneficial insects. Farmscaping with sunflowers, peas, vetch, buckwheat or small grains, to encourage ladybugs and lacewings, can make insect control unnecessary in a good year. Ground beetles and bats can consume surface and air attackers before you even need to look.
  3. Monitor your crops regularly at least once a week and identify any pests you see.
  4. Introduce natural enemies of the pest (bacteria, fungi, insect predators or parasites). Try biofungicides for use against some diseases. F-Stop, T-22G Biological Plant Protectant Granules or other forms of Trichoderma can control Rhizoctonia, Fusarium and Sclerotonia. Soil-Gard (Gliocladium virens) can work against Rhizoctonia. Bacillus subtilis works against Rhizoctonia, and Sclerotonia. Mycostop (Streptomyces griseoviridis) can be used against Phytophthora, Alternaria, 35% hydrogen peroxide diluted to a 0.5–1% foliar spray solution may help control early blight. 1% solution = 3.7 oz in 124.3 oz water to make one gallon (1 ml:33 ml). There are commercial products such as Oxidate that are based on hydrogen peroxide, which is corrosive and challenging to handle.
  5. Hand pick (or trap) and kill the pests if the pest population is above the action threshold. Many fruit and root crop plants can take 30% defoliation before suffering any loss of yield. Where the crop is the foliage, this may be too much, but people don’t east potato foliage!
  6. Use biological controls (often derived from natural enemies) if the damage is still economically significant after trying the earlier steps in the process, including Spinosad or Bt.
Colorado potato beetle on an eggplant leaf.
Photo Pam Dawling

Potato Pests

Potatoes can be attacked by more than 150 insect pests. But don’t despair! In each region there are only a few species that could cause unacceptable losses of yield or quality. These losses can result either directly from the insects or indirectly by transmission of diseases.

Colorado potato beetle is the most common pest that potato growers get to deal with. The pink blob-like larvae of this beetle can eat enormous amounts of potato leaves while growing into bigger pink blobs. Left alone they can kill a planting. Acceptable amounts of defoliation without causing loss of yield are surprisingly high: 50%–75% of the top leaves on a young 6″–8″ (15–20 cm) plant, 25% on a 12″–16″ (30–40 cm) plant, a mere 10% at the critical full bloom stage (when the tubers are sizing up), and up to 25% once full grown. As with many pests, having a few of them is not important — it’s all about the numbers. Action to control CPB is only needed if the number of adults or larvae is higher than 1.5 per plant or egg masses exceed one per ten plants.

Crop rotation is effective, because Colorado potato beetles overwinter as an adult in the soil and when they emerge they have to walk around searching for a potato plant. CPB can have 1-3 generations a year. Even where two or three generations are usual, a significant portion of the summer generation adults go directly into the soil and become dormant. Eggs are laid in clusters of 20 or more. They look like ladybug eggs but are a stronger orange color – don’t kill the wrong ones! The beetle can go from egg to adults in as few as 21 days. There are four larval instars, with 75% of the total foliage destruction caused by the final and fattest instar.

Colorado Potato beetle late stage larva or pupa.
Photo Pam Dawling

Mulching with hay or straw can prevent CPB finding your potato plants – we never find them on our summer planting. Our unmulched spring planting is a different matter. I scout that field once a week, counting adults and larvae on a hundred randomly selected plants. As soon as I see more than 50 adults or 150 large larvae or 400 small larvae per 100 plants, I unpack the sprayer. I do a spraying with Spinosad, a fermentation product of a soil bacterium. It kills insects by over-stimulating their nervous systems. Spinosad kills a wide range of helpful and harmful insects too, so spray in the early morning or late evening when bees are not flying. Shake the bottle well, and mix following the instructions. Clean and triple rinse the sprayer. Do not flush in the creek or pond. Repeat in 6 days, but only if needed. Usually one spraying is enough, although I continue weekly checks. In the South, there can be three generations of CPB each year, so stay vigilant.

Prior to using Spinosad, we used Bt. The version of Bt for CPB nowadays is Bacillus thuringiensis var. tenebrionis. The kurstaki strain (such as Crymax) generally available in small quantities previously is genetically modified, so we stopped using it, not wishing to be part of any support for GMOs.  Neem and Beauvaria bassiana can also kill CPB larvae.

Flaming when the potatoes are less than 8” (20 cm) tall, is another effective control measure for CPB. Choose a warm sunny day when the pests are at the top of the plants. Flaming can kill 90% of the CPB adults and 30% of the egg masses, according to Colorado Potato Beetle: Organic Control Options – ATTRA

Young eggplant struggling against lots of aphids.
Photo Pam Dawling

Insects with piercing-sucking mouthparts damage potatoes by physical injury to the leaves, sucking out phloem, injecting their toxic saliva and possibly transmitting diseases. While potatoes can grow new leaves, there is still damage to plant health. Direct injury by sap-feeding insects can kill the plant. Soil-dwelling insects have only minor effects on yield, generally, but can reduce tuber quality and storage life.

Aphid-transmitted viruses cause greater losses than all other insect-related damage together. There are at least 9 aphid-transmitted potato viruses. Aphids can be reduced by farmscaping, planting flowers which attract ladybugs, lacewings and other aphid-eating insects.

Clover flowers attract beneficial insects. Red clover in June.
Photo Pam Dawling

Potato leafhoppers are a bad problem in central and eastern North America. They overwinter on the Gulf Coast. In spring, flying adults are transported north on upper level airstreams. Yield loss can occur before visual symptoms are obvious. Leafhoppers can cause leaves to shrivel and die. The initial effects are reversible if leafhoppers are controlled before leaf tissue is destroyed (“hopperburn”). By reducing the green leaf area, hopperburn affects photosynthesis and growth. The most vulnerable stage is when the tubers are bulking up. Leafhoppers can also transmit diseases. Trichogramma wasps parasitize leafhopper eggs. Garlic with insecticidal soap, sprayed early in the morning, especially on the undersides of the leaves, can control hoppers.

Potato psyllid occurs in the western U.S. Damage to the roots and tubers is caused by feeding nymphs, which can cause psyllid yellows. The first symptoms of psyllid yellows include stunting, loss of green color, leaflet distortion, reddish discoloring of new leaves, and the appearance of aerial tubers. Early action can stop and even reverse the damage. Adults cause little to no damage underground.

Wireworms (click beetle larvae) can tunnel through the tubers. Wireworms can live for 1-3 years, so crop rotation is important. Avoid planting potatoes the first year after turning under pasture or lawn. If you expect to have wireworms, plant small whole seed potatoes rather than cut pieces. Cut slices of potato can be used to trap wireworms (dig up the trap pieces each day and kill the wireworms.

Cutworms can eat the leaves from the bottom of the plant up (the opposite approach from CPB larvae). Once the plants are fully grown, up to 75% loss of lower leaves is unimportant. At earlier stages, if any cutworm damage is seen, dig around the stem, find and kill the cutworms.

Blister beetles can cause trouble later in the season, skeletonizing leaves and spreading a wilt. They contain cantharadin, which can cause blisters on the skin of unwary workers. Blister beetles can be trapped in crops of chard or beets next to the potatoes. The beetles are easier to see and catch in the trap crops than in potato foliage. If there aren’t too many it may be worth putting up with them, as their larvae are carnivorous and eat grasshopper eggs.

The potato tuber moth damages both foliage and tubers during growth, but the biggest losses occur in storage. Larvae inside the potatoes can continue their development in storage, filling the tubers with frass and letting in decay organisms. When commercial infestations are high, the crop is not worth harvesting because of labor costs to cull out the infested tubers.

 Nematodes can be deterred by choosing appropriate preceding cover crops, or by applying 1-2 tons/ac (2240-4480 kg/ha) of crushed mustard seed meal to the soil before planting. This will also reduce early weeds and act as a fertilizer. 

Potato Diseases

Before a plant can become diseased, three conditions must exist: a susceptible host, a disease organism, and a suitable environment for the pathogen. The choice of the disease control method should be based on an accurate identification of the pathogen and the disease.

Late blight on a potato leaf. http://blogs.cornell.edu/livegpath/gallery/potatoes/late-blight/

Late Blight (Phytophthora infestans) is by far the worst disease to afflict potatoes. This is the disease that contributed to the famine in Ireland (caused by the profiteering of the English land-owners, who sold the barley and left the tenant farmers to subsist almost entirely on potatoes). The disease is caused by a species of a fungus-like oomycete or water mold (previously considered a fungus, now reclassified as protozoa) that blows in on the wind. It is worse in warm wet weather with cool nights. Late blight starts as “water-soaked” spots on the leaves. These expand into gray-black “scorched” areas, sometimes with a dotted white mold growth, especially on the underside of the leaves. Cut stems reveal a dark circle of infected tissue. The disease spreads rapidly, turning plants black, as if badly frosted, and can kill an entire planting in ten days unless stopped by hot dry weather.

The best defense is to always remove volunteer nightshades from your fields and compost or bury all crop debris. The disease spreads via cull piles, nightshade plants and petunias — it needs live plant material to survive. If you find volunteer potato plants popping up in early spring, it is best to pull them up! Spores survive winter in warmer climates and then blow north and uphill. Preventive action may be taken with sprays every five days of (toxic) copper products, hydrogen peroxide, Bacillus pumilus or Bacillus subtilis products.

If Late Blight occurs late enough in the season, you can save your crop by mowing off the foliage, raking it off and disposing of it, and leaving the field untouched for two weeks before harvesting whatever potatoes have grown. This prevents the spores getting into the soil and infecting the tubers. Disposing of large amounts of blighted foliage is no easy task. When I had to deal with Late Blight, back in the 70’s, we made a fire and gradually added more tops as the previous ones burned. This was a very smoky fire, polluting, and no doubt contributing to global warming. Digging a big hole and burying it all is probably better.

Early Blight (Alternaria solani) is a common fungal disease, which mostly affects stressed or older plants. It starts as small brown spots on the lower leaves, which conglomerate into brown blotches that are restricted by the leaf veins, and so they can be angular in shape. The lesions have a bullseye appearance – concentric circles with a yellow halo around each one. During warm humid conditions, the fungus steadily defoliates the plants, reducing yields. The disease is seed-borne, soil-borne and airborne, surviving on plant debris and nightshade weeds. Early blight (Alternaria solani) can appear late in the season, not just early, despite the name. The manifestation of blight symptoms can be minimized by growing strong healthy plants, supplying sufficient water, and spraying with compost teas. The beneficial fungus Trichoderma harzianum can give good results.

Black Scurf or Stem Canker fungus (Rhizoctonia solani) is worst in cold wet soils. Early in the season it can cause sprout death. On older plants, red-brown stem lesions develop into cankers, and the infection can spread to the tubers, which then become cracked and misshapen, and may have dead tissue at the stem end. There may be firm black sclerotia (small dried reproductive bodies) on the tuber. In future, get disease-free seed potatoes and wait for the soil to warm a bit before planting.

White Mold (Sclerotinia sclerotiorum) on the vines. If you want to prevent this in future, you could dust the seed pieces with the commercially available fungal antagonists Trichoderma viride and Trichoderma virens.

For a chart with about 30 potato diseases, see The Potato Association of America, Commercial Potato Production in North America 2010

A lady bug on a potato leaf, perhaps producing larvae to help control aphids.
Photo Kathryn Simmons

Hoophouse Musings, Bugs, Okra, Edible Landscaping Workshops in Maryland

Hoophouse beds in December. This is why we have a hoophouse!
Photo Wren Vile

Winter hoophouse posts in Mother Earth News newsletter

Sowing and Transplanting Winter Crops in a Hoophouse

Grow Great Lettuce in Winter

Winter hoophouse lettuce
Photo Kathryn Simmons

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A photo of a Tiny House from Wikipedia

Would you live in a hoophouse?

A reader wrote in:

“I have actually been thinking of building a tiny house and putting it inside a big hoophouse, creating a living area that would include a yard, trees, and gardens – allowing me to snowbird in place in northern New England – but I’m concerned about outgassing, since I’d be there almost 24-7 most days (I work out of my home). Have you done any research on outgassing of hoophouses?”

A Tiny House is generally a residential structure under 400 sq. ft

First off, No I haven’t done any research about hoophouse off-gassing, but I wouldn’t worry about out-gassing from the polyethylene of the hoophouse. Other products  are much closer to your nose: All the materials used to construct, preserve and decorate the house and all the products within the house, such as furniture,  fabrics, soaps, appliances etc.

There are some other things I’d wonder about:

1.      Temperature. When the sun shines, the interior of the hoophouse warms up. When the sun doesn’t shine, it doesn’t. Would you heat the tiny house? You’d have to avoid heating systems that could damage the plants.

2.      Snowfall. When it snows, you need to remove the snow from the roof of the hoophouse. Some snow can be carefully pulled down from the outside. Usually we also walk around inside the hoophouse bouncing a broom on the inside of the plastic to move the snow off. You can’t do that if you have a house in the way.

3.      Humidity. In the winter we grow cold-tolerant hoophouse crops. We are aiming for 65 F (18C). We need fresh air for the plants and to deter fungal diseases. It doesn’t work to keep the hoophouse sealed up and “cozy”!

4.      Strong winds. In hurricanes and gales, hoophouses sometimes collapse or get destroyed. You don’t want to be inside when that happens.

5.      Height. Our hoophouse is less than 14 ft (4 m) at the apex.

In conclusion I’d say it’s better to have a small patio seating area within your hoophouse for suitable sunny days, rather than plan to live inside all the time.
Brassicas in a nematode-fighting hoophouse crop rotation in Hawaii.
Credit Gerry Ross, Kupa’a Farms

Do you value crop rotation in your hoophouse?

A reader in the Pacific Northwest wrote: “This winter I have been re-thinking my crop rotation plan after having some issues (with flea beetle larvae in the soil outsmarting my diligent insect netting of my brassica salad crops). These days I see intensive market gardeners seeming to not worry so much about rotation (i.e. Neversink farm, etc), and yet I’ve always been taught that it is such an important principle to follow. I reviewed your slideshows on crop rotation and also cool crop planning in the greenhouse (which briefly addresses salad brassica rotation with other crops). With how much space I have and the high demand I have for brassicas, for salad mix (mustards) and also the more mainstay cole crops, I had settled on a 2.5 yr between brassica crop rotation (but planting two successions of mustards in the same bed within one year, in the year the bed was in mustards, with a lettuce or other crop breaking up the successions, with the idea that they were very short day and also light feeder crops). Wondering if you think this just doesn’t sound cautious enough, or if this sounds like a reasonable compromise with not having more space to work with (and wanting to satisfy the market demand for brassicas).”

I replied: “Yes, I do think crop rotation is important. I do know some farms seem to have given it up. I think what you are seeing shows one reason why rotation is important. In our hoophouse, we do as you do, allocating brassicas to a space for that winter season and perhaps doing more than one round of brassica crops. Then moving away from brassicas for the next two winters. If doing that doesn’t get rid of the flea beetle problem, and you are being thorough about netting with small-enough mesh netting (sounds like you are, but maybe check the mesh size), then my next step would be spinosad when the flea beetles appear. You can spray the inside of the netting too, and close it quickly. It’s that or a longer rotation, which it sounds like is not financially viable. You could also try farmscaping and/or importing predatory insects (not sure if there are any), Are there beneficial nematodes that attack flea beetle larvae? These are things I don’t know about, but might be worth looking into.”

 

Late sweet corn and sweet potatoes
Credit Ezra Freeman

Sweet Potato fends off bugs

Modern Farmer has this fascinating article about sweet potato plants alerting their neighbors to pest attacks.

Researchers from the Max Planck Institute and the National Taiwan University found that when sweet potato plants are attacked by insects, they emit a bouquet of odors and start production of a protein called sporamin that makes them unappetizing. Neighboring sweet potatoes sense the odors and start their own production of sporamin.


 

A new Tokyo bekana transplant attacked by vegetable weevil larvae October 10
Photo Pam Dawling

Insect damage cause stress-response production of anti-oxidants

In a related piece of news, Agrilife Today from Texas A&M AgriLife Research has found some evidence that wounded plants produce anti-oxidants as a stress response, which may make them healthier for human consumption. Read the report here.

Edible Landscaping with a Permaculture Twist Spring Series

Michael Judd in cooperation with Common Market CO+OP is presenting a combination of hands-on workshops at Long Creek Homestead and evening talks at the Common Market, Frederick Maryland.

Click here for info on Spring Workshops/Talks/Tours

·        Inoculating Mushrooms

·        Fruit Tree Grafting

·        Herb Spirals

·        Creating Growing Beds- Swales and Hugelkultur

·        Edible Landscaping & Straw Bale Home Tour

·  For the Love of PawPaws


 

Fire Ants have reached Toronto

A reader wrote in that the European Fire Ant is now found in Toronto.


“There were two nests of these in my allotment garden 2018.
They actually moved the nest in order to be closer to the zucchini
plants.  Hand on heart: I never had  any cucumber beetles develop past
the instar stage.  The ants did not eat the eggs but they ate the larvae
as soon as they hatched.  Same for potato beetle.  My neighbours had
the best cucumber harvest in history. 
What I’ve read is these Fire Ants kill colonies of native ants.  Summer 2019 I had a Pavement Ant war that went on for days.  Clearly the Fire Ants did not wipe them out.  There are black ants and other smaller red ants
in my garden.  The Fire Ants appear to have moved on for some reason known
only to themselves.   Perhaps they too have enemies.”
“There’s a guy with a Youtube channel who keeps ant colonies.   AntsCanada although he is in the Philippines.  What happened was the feral Pharaoh Ants invaded his colony of Fire ants and killed them.  Pharaoh Ants are much smaller but perhaps that’s what gave them the advantage.   We have Pharaoh ants in Toronto also.   I spend a lot of my time looking at the little critters in my garden.  Like red velvet mites:  there were many in 2016.  Have not seen a single one in two years now. “

Video of Okra Taste Testing

Chris Smith, author of The Whole Okra

Chris Smith, author of  The Whole Okra: Chris has a video of
the taste testing on  Youtube, https://www.youtube.com/watch?v=sAy0pouxlME