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

Cooking Greens in April

Cooking Greens to Harvest in Central Virginia in April

Out with the old! In with the new!

A bed of spring Senposai.
Photo by Wren Vile

Outdoors, collards, kale and spinach that have over-wintered will be coming to an end. Most years, the collards and then the kale bolt in mid-late March, and the overwintered spinach in April.

Fast growing crops like mustard greens and senposai from spring transplanting will be ready to harvest as leaves from early April; collards and kale from mid-April. Beet greens might be ready at the end of April, or it might be May before we get those, depending on the weather and our sowing dates.

From the hoophouse, we are getting the last of most of our indoor greens. The Russian kale, the chard and the Frills (frilly mustards) are bolting. We do have spinach we sowed in January, which will continue all this month. The Bulls Blood beet leaves no longer look very appetizing, but we could cook those up early in the month. The milder winter means earlier bolting this year.

Cooking Greens to Sow in Central Virginia in April

Bright Lights chard in our garden in July.
Photo Pam Dawling

Chard is our best summer cooking green. Chard (Beta vulgaris var. cicla) is the same species as beetroot and, like beets, is a biennial. Hence it will not flower until the second year after planting, and can provide fresh greens all summer and fall, until halted by hard frosts. Even then, the root may survive and regrow the next spring. Leaf beet, also known as perpetual spinach, is a chard, with thinner stems and smaller leaves than most Swiss chard. It is the closest in flavor to spinach for growing in hot weather

Leaf Beet (Perpetual Spinach)
Photo Fedco Seeds

If you prefer spinach in spring, as we do, grow that first, and switch to chard for summer, sowing in plug flats or soil blocks three weeks before your last frost date. (We sow March 24-April 6)

If you want chard in spring, you can start flats earlier or direct seed outdoors two or three weeks before the last frost date.

We also use beet greens for cooking, although our main purpose is to grow beets. Our last date for sowing beets in spring is 4/15.

There are other hot weather greens you could sow in central Virginia and warmer climates.

In the hoophouse, it is definitely too late to plant cooking greens. Anyway, we are filling the tunnel with early tomatoes, squash, cucumbers, and peppers.

Cooking Greens to Transplant in Central Virginia in April

Broccoli head after rain
Photo Wren Vile

Outdoors, we transplant our main cabbage and two sowings of broccoli under nets or rowcover within 6 weeks of sowing. Rowcover is our usual choice, because changeable weather and late frosts are more of an issue here in spring than bugs are. It is important to protect young cabbage and broccoli with 5-8 true leaves from cold stress (<40°F/4.5°C for a few days, or longer at 50°F/10°C). At this stage they are particularly sensitive to cold, which can cause early bolting (and very low yields). After a few weeks, when the weather is more settled, we move the rowcover to newer, more tender crops.

Mid-April: We use saved extra transplants to fill gaps in the broccoli and cabbage plot, at the same time planting out alyssum every 6’ (1.8 m) in the center of the beds. These little flowers attract beneficial insects (see more below).

Ruby Red chard.
Photo Kathryn Simmons

Late in April we will transplant leaf beet and chard – it doesn’t take long for the seedlings to grow. Often we cover the prepared bed with hay mulch, then make two rows of “nests” in the 4’ (1.2 m) wide beds. We don’t space the rows evenly across the bed, but bunch them in close to each other in the middle. This saves the paths for us to walk down.

In the hoophouse, in very early April we use young spinach transplants to fill gaps only in the outer thirds of the beds, leaving the bed centers free for the tomatoes, etc. It would be better to have done this in late February and March, but this year we didn’t get to it. We won’t get high yields, planting this late.

Other Cooking Greens Tasks in Central Virginia in April

Early April: We move rowcover from turnips, senposai, early cabbage, kohlrabi and onions as needed for the broccoli and the maincrop cabbage.

Mid-April: We move rowcover from spring-planted kale, collards, mustard and early lettuce for the tender crops. We finish filling gaps in the broccoli and cabbage plot, at the same time planting out alyssum (sown March 3) one plug every 6’ (1.8 m) in the center of the beds. See the Special Topic for April below, for more on farmscaping, as this method of pest management is called.

Early spring cabbage with alyssum to attract beneficial insects.
Photo Pam Dawling

Late April: We move rowcovers from for the broccoli and the maincrop cabbage. With broccoli, the first weeks after transplanting are vegetative growth, adding leaves until there are about 20, when “cupping” starts — the leaves start to curl up, forming a convex shape rather than growing straight out. The cupping stage is usually10-14 days before harvest starts, depending on temperature. If the weather gets too hot — more than 80°F (27°C) — too soon, the broccoli may grow only leaves, and not head up.

In the greenhouse, we start to have less work, which is fortunate as outdoor work increases.

Special Cooking Greens Topics for April: Farmscaping for Brassicas

Farmscaping is the inclusion of specific flowers to attract beneficial insects. The pollen and nectar offer an alternative food source to beneficial insects when their insect prey is scarce. And if their insect prey is right by the flowers, what could be better?

Alyssum.
Photo Raddysh Acorn

We plant Sweet Alyssum in our spring broccoli patch to attract predators of aphids and caterpillars; Putting 5 percent of the crop area in plants that attract beneficial insects can seriously reduce pest numbers. Sweet alyssum, yarrow, dill, coriander (cilantro), buckwheat, mung beans, other peas and beans, black oil-seed sunflower, calendula and cleome all work well to attract a range of insects (especially ladybugs and lacewings) that eat or parasitize aphids. Pans of water and gravel will help attract aphid midges and lacewings. The gravel provides surfaces for the insects to land on while drinking. Farmscaping can make other insect control unnecessary in a good year. Beneficials will generally move up to 250 feet (75 m) into adjacent crops.

We also plant “insectaries” around the garden, usually at the ends of beds with crops that will be growing for several months. These flowers are planted inside rings sawn from a plastic bucket. The rings alert the crew that something special is there, not just a clump of weeds. Mix flowers to have something blooming all the time.

Insectary circle with sunflower, tithonia, borage, zinnia.
Photo Pam Dawling

Another method for incorporating farmscaping is to plant beneficial-attracting perennial flowers in areas that are too challenging to use for production: edges, slopes, tight corners, hedgerows, and field borders.

Other Pest Management for Brassicas

Using rowcovers keeps many pests off the plants while they are small. We have not had much trouble with aphids, perhaps partly because our overhead sprinklers wash them off and they can’t travel far. Insecticidal soap sprayed three times, once every five days, can usually deal with aphids. Our worst pest is the harlequin bug. For lack of a better organic solution, we handpick them. Ladybugs are reputed to eat harlequin bug eggs.

Sometimes we have had enough cabbage worms to make Bt (Bacillus thuringiensis) necessary, but usually paper wasps eat the caterpillars. The action level threshold is an average of 1 cabbage looper, 1.5 imported cabbageworms, 3.3 armyworms or 5 diamondback moth larvae per 10 plants. Below this level you can do watchful waiting rather than spraying with Bt or spinosad. We are lucky enough to have the naturally occurring wasp parasite of cabbage worms, the Braconid wasp Cotesia species, which are found as small cottony white or yellowish oval cocoons in groups on brassica leaves. The Cotesia wasps like umbelliferous flowers, and overwinter on yarrow as well as brassicas. If you find Cotesia cocoons in the fall and your brassicas aren’t diseased, you can leave plants in the field over winter. Or you could collect up leaves with cocoons in late fall and store them at 32°F–34°F (0°C–1°C) until spring. Hopefully no one will clean out your fridge without checking.

Richard McDonald has good information in his Introduction to Organic Brassica Production. He reports that broccoli plants with six to sixteen leaves (just before cupping) can lose up to 50 percent of their leaf area without reducing yield. Moderate defoliation (20–30 percent) causes the plant to exude chemicals that attract parasitic wasps and predatory insects. If you relax and allow this amount of defoliation early on, you can encourage these beneficial insects to move in and begin foraging in the area. Once the plants cup, you want to prevent further defoliation by having the most beneficials and the fewest pests on site. If pest levels are above the action threshold, cupping is the stage to take action, and probably not earlier.

Broccoli side shoots offer harvest after the main head is cut.
Photo Nina Gentle

To float out worms and aphids after harvest (before cooking!), use warm water with a little vinegar and soak for up to fifteen minutes, then rinse.

Insectary flowers to attract beneficial insects

Sunflower bee and bug. Photo by Bridget Aleshire
Sunflower bee and bug. Do you know this bug?
Photo by Bridget Aleshire

As part of our strategy to entice pollinators and other beneficial insects into our garden, we plant selected flowers among the vegetables. On a big scale this is known as Farmscaping, and you can read about it in a publication from ATTRA; “Farmscaping to Enhance Biological Control – IP065” It’s 99c for the download unless you are a subscriber, or if the cost is beyond your budget. Oregon State Extension has a 40 page year 2000 version online.

We plant Sweet Alyssum with our spring broccoli and cabbage to attract insects that prey on aphids. This works very well. We plant one Alyssum plant per 8 broccoli or cabbage plants in the center-line of the bed, between the two rows of brassicas. We sow it in the greenhouse in early March, around the time we sow replacement broccoli and cabbage, and transplant in mid April when we do the gap-filling, replacing any brassica casualties, 2 or 3 weeks after transplanting the brassicas. We have to explain carefully to our helpers not to weed them out, or smother them with mulch when we move the garlic mulch over to top up the brassica mulch.

As you’ll see in some of the photos, we do also grow some repellent flowers (nasturtiums, french marigolds) and some trap crop flowers (cleome for harlequin bugs) but I’m not going to talk about those today.

Insectary circle at the end of a bed of chard. Photo by Bridget Aleshire
Insectary circle at the end of a bed of chard.
Photo by Bridget Aleshire

Plants with small flat open flowers, like alyssum, dill, yarrow, buckwheat, sunflowers, cosmos can attract ladybugs, lacewings, aphid parasites, damsel bugs, braconid wasps, rove beetles, syrphid flies, and spined soldier beetles. This is a rather loose and general statement. you can read the ATTRA publication to make a specific plan to tackle particular pests. Ladybugs are a good general help because they eat the eggs of many different pest species.

At the end of April we sow several plug flats of different flowers to plant out in Insectary Circles at the ends of our raised beds. We include borage, dill, calendula, cosmos, sunflowers zinnias and tithonia in that sowing, and hope to plant them out in mid-late May, after the big push to get all our tender transplanted crops out. We used to sow earlier, but we find ourselves too busy to get them transplanted at the right stage of growth, so it’s better for us to hold off and sow later.

Insectary circle in an okra bed. Photo by Bridget Aleshire
Insectary circle in an okra bed.
Photo by Bridget Aleshire

We choose beds where the crop will be in place for a long stretch of time, hopefully to the frost date. This includes tomatoes, eggplant, okra, chard, leeks.  Because our focus is on food crops and we are always too busy, we have evolved a method that uses little time and reduces the chance of things going wrong. As mentioned above, we get a lot of help in the garden from visitors and people who help out for half a day a week, so we need to make the flowers obvious to prevent over-zealous weeding. The main way we do this is to take old plastic buckets and saw hoops from them. We set the hoops in the soil and plant he flowers very close together inside the hoops. This marks them out as something special. And it really works fine to have the flowers just 2 or 3 inches apart.

Insectary flower planting day is ideally one when rain is expected at night, as otherwise it’s a fussy job to tour all the circles with a watering can every day. We take a wheelbarrow and set the flats leaning out the sides like wings. Some kinds of watering cans can be carried on wheelbarrow handles. that helps. The hoops can also go on the wheelbarrow handles. Then we  work our way along the driveway, finding suitable beds. We dig with a trowel to make a circle big enough to set the hoop in, and pile any extra soil inside. Then we plant a selection from our flats, water and move on.

After the driveway, we work along the center path between the east beds and the west beds and then back along the east side, where there is a path. We hope to find a suitable spot every 25 feet or so. if it doesn’t rain, we do hand-water daily until each circle has had a good soaking from night-time sprinklers or rain.

We haven’t made a scientific study of whether these flowers do attract more beneficial insects than we had previously, but we do enjoy seeing the flowers, and I firmly believe that diversity of species helps the ecosystem.

Borage in an insectary circle. Photo by Bridget Aleshire.
Borage in an insectary circle.
Photo by Bridget Aleshire.

 

Planting spring broccoli, farmscaping, BMSB

Flats of broccoli seedlings in our cold frame. Photo Kathryn Simmons
Flats of broccoli seedlings in our cold frame.
Photo Kathryn Simmons

We’re mid-way through transplanting spring broccoli. It’s been a challenging “broccoli-planting season” with two very cold nights (20F and 22F) since we started, some high winds (very cold and drying, hard to keep the rowcovers in place). In order to have as long a broccoli harvest period as possible, we use several varieties with different days-to-maturity, and do two sowing dates. This spring we are using the following varieties:

Tendergreen broccoli Credit Fedco Seeds
Tendergreen broccoli Credit Fedco Seeds

Tendergreen (47 days from transplanting),

Green King broccoli Credit Fedco Seeds
Green King broccoli
Credit Fedco Seeds
Green Magic broccoli Credit Johnnys Seeds
Green Magic broccoli Credit Johnnys Seeds

Green Magic (57 days), Green King (65d), Arcadia (68d) and Diplomat (also 68d).

 

 

 

Arcadia broccoli Credit Johnnys Seeds
Arcadia broccoli Credit Johnnys Seeds
Diplomat broccoli Credit Johnnys Seeds
Diplomat broccoli Credit Johnnys Seeds

These are all varieties we’ve grown before and had success with. Tendergreen is exceptionally fast, and gets us off to a good start. It’s not heat tolerant, however.

Note that the catalogs give different days to maturity. Sometimes these are from sowing. We’ve calculated our own for comparison.

We sowed our first round of broccoli on February 10 to transplant April 4, and our second round (a repeat of the first) on February 24 for transplanting April 10. For insurance we do a (smaller) third sowing of the two fastest varieties on March 6 to fill gaps on April 25. Well, the plants in the flats looked great! We delayed the start of transplanting because of the weather. We transplanted on April 4 and April 9. The first planting suffered  from the two very cold nights I mentioned, even with thick rowcover. So last week we replaced casualties with plants left over from the initial planting. (We spot out 20% more plants than calculations say we need.) We had 20 flats of 40 plants for each of the two plantings. Today we will plant the second half of the patch, over a week later than originally planned.

The third sowing has been in the cold frame for about a week. We like to give them two weeks to harden off. In another week we’ll go through and replace casualties throughout.

Sweet Alyssum Credit Southern Exposure Seed Exchange
Sweet Alyssum
Credit Southern Exposure Seed Exchange

At the same time we’ll transplant Sweet Alyssum in the centers of the broccoli and cabbage beds, about one plug every 6ft (it’s easiest to count 4 broccoli plants, then plant an alyssum). These little plants attract beneficial insects. You can read about Virginia State University research into Farmscaping. ATTRA also has a good publication.

Alyssum attracts the Syrphid fly and the Tachinid fly, predators of aphids and caterpillars.

 


We do other farmscaping too. We sow rows of sunflowers wherever we find space and nasturtiums with cucumbers and squash. We also transplant “Insectary Circles” with a mix of borage, cosmos, calendula, tithonia, dill, zinnias and cleome. We sow these in the greenhouse in plug flats in late April or early May and transplant in late May. If we had more time we could do it earlier. We found that sowing earlier was a mistake for us, as we don’t get around to finding time to transplant them until after the warm weather vegetables have been planted out. We choose beds with long season crops, (meaning ones that will be there a long time) to avoid problems trying to till around the circles. We cut bottomless circles from old plastic buckets, sink these in the soil at the end of a bed, and plant into them. This helps avoid the problems that can come with novice weeders!

Harlequin bug nymphs on spider flower (Cleome); note, white flecks in the leaf typical of feeding by true bugs Credit Missouri Botanical Garden
Harlequin bug nymphs on spider flower (Cleome); note, white flecks in the leaf typical of feeding by true bugs
Credit Missouri Botanical Garden

Cleome (spider flower) can be used as a trap crop for Harlequin bugs.(You still have to deal with the infested cleomes, but it keeps your brassicas free). The Missouri Botanical Garden has great info on Harlequin bugs.


Adult female brown marmorated stink bug. Credit Rutgers New Jersey Ag Station
Adult female brown marmorated stink bug.
Credit Rutgers New Jersey Ag Station

While one the subject of bugs and stink bugs in particular, I read some recent information on Brown Marmorated Stink Bugs in an eOrganic article on the eXtension site. They even have a video. The good news is that jumping spiders, ground beetles and earwigs have been observed eating the egg masses of BMSB, assassin bugs attack the nymphs, and  the predatory spined soldier bugs eat both the eggs and the nymphs of BMSB. This is so much better news than the early days of the invasion, when it seemed like nothing would touch them.

But I don’t want to close with a picture of a pest, so here’s more broccoli. Yes, it’s under the rowcover!

Spring broccoli under rowcover. Credit Kathryn Simmons
Spring broccoli under rowcover. Credit Kathryn Simmons