Nematode-resistant food crops and cover crops

Golden Frills and Scarlet Frills, two Juncea mustards that resist nematodes. Photo Pam Dawling

A few weeks ago I wrote about clearing tomato plants, and mentioned our hoophouse troubles with nematodes. Nematodes are tiny soil-dwelling worms that have a wide host range and are hard to control. They move only 3’–4′ (1–1.2 m) per year on their own, but people move them on shoes, tools, etc. We have had peanut root-knot nematodes (Meloidogyne arenaria) since 2011 when we found them in spinach transplants we were growing for outdoors in early spring.

My article on nematodes in Growing for Market  in November 2014 describes our discovery of the beasties and our first attempts to deal with them.

White Russian kale in our hoophouse.
Photo Pam Dawling

In my August 2014 post Good news – great hoeing weather! Bad news – more nematodes in the hoophouse I wrote about solarization to fight nematodes in our hoophouse (scroll down to the end of the post). The post includes a photo of our first attempt at solarizing – a  bit of a How Not To! Be sure to use UV-inhibited polyethylene. This year we somehow got some construction plastic mixed in. It doesn’t work! It goes cloudy (thus not heating up the soil) and it shatters into little pieces.

There is info on dealing with nematodes from Garry Ross in Hawaii, where nematodes are a fact of daily life, in my post Cold weather, snow, thinking about nematodes from February 2015.

My most thorough blogpost about nematodes was in 2018 for Mother Earth News:  Managing Nematodes in the Hoophouse.

Solarizing with clear plastic. Photo Pam Dawling

My post Solarization and crop choices to fight nematodes in August 2019 includes a photo of a much better way to solarize an individual bed. In that post I gave a list of nematode-resistant food crops, and also talked about cover crops. There is a photo of nematodes on cucumber roots there too).

Food crop choices to fight nematodes

Most resistant and most helpful are the Juncea group of mustards. I did some research into more Juncea options in Solarization and crop choices to fight nematodes. We don’t like very pungent greens, so we have not yet taken the route of planting a whole bed of Juncea types. Instead we have mapped and flagged the nematode-infested areas of our beds, and try to be mindful of what we plant in those spots. Three of our seven beds have no nematodes so far.

Open-pollinated Yukina Savoy.
Photo Ethan Hirsh

This year we looked at the nematode map we had made and decided to focus our attention on the bed with the highest number of nematode patches, and grow the most resistant winter crops (of the ones we like to grow) there. That’s the frilly mustards (Ruby Streaks, Scarlet Frills, Golden Frills, all Juncea mustards, and Mizuna, a Japonica mustard), Yukina Savoy (variously reported to be Brassica juncea,  Brassica rapa pekinensis, and Brassica rapa), and Russian kales (Brassica rapa).

Mapping nematode areas

See the post with info from Gerry Ross I mentioned above. We have previously tried for a “Two years good, One year bad” strategy. This was to grow nematode-resistant crops in the infected areas for two years, then try risking one year of susceptible crops. That was a bit demanding on careful management, and we haven’t kept that up.

Nematode map 2022

Cover crop choices to fight nematodes

French marigolds and sesame to deter Root Knot nematodes in our hoophouse. Photo Pam Dawling

A reader asked about cover crop choices to fight nematodes. In June 2019 I wrote about using marigolds, sesame, Iron and Clay cowpeas as warm-weather nematode resistant cover crops. We’ve also used winter wheat (in winter!), and white lupins (not worthwhile, in my experience). See that post for a few other ideas on nematode-fighting cover crops, and why we decided against some options. At that time, we decided not to grow sunnhemp (Crotolaria) because it is poisonous, although newer varieties of Crotolaria have lower toxin levels. More recently we have been growing sunnhemp, after I saw it growing so well in North Carolina. It is a warm-weather legume, so it is feeding the soil while tackling the nematodes. It does grow tall in the hoophouse, and we have taken to chopping it down with hedge shears to an ergonomic elbow-height every few weeks whenever it gets too tall. The cut tops create a nice “forest-floor” mulch effect. You can almost feel the extra organic matter nurturing the soil! (High OM levels deter nematodes.) 60-90 days to maturity.

Sunnhemp cover crop at Nourishing Acres Farm, NC.
Photo Pam Dawling

We previously used soybeans as a short-term leguminous summer cover crop, but they do not offer the nematode resistance. Iron and Clay, Mississippi Silver and Carolina Crowder cowpeas are all nematode-resistant and can be grown in summer instead of soybeans. Sesame is a legume that is particularly good against peanut root-knot nematodes.

Iron and Clay southern peas flowering in September. Photo Pam Dawling

See Our Organic Integrated Pest Management post for an organized approach to pest management, including nematodes.

A Florida reader gave me information about partridge peas, which I have not yet tried: After terminating cool-season brassicas and celery between April and June, their late spring sowing of partridge peas were too late this year to be productive, because the hard seed was very slow to germinate. Partridge pea could be a good cover crop for mid- to late-summer, if you scarify those hard seeds to speed germination.

Some cover crops can be alternate hosts for pathogens like cercospora, rust, or bacterial leaf spot, so be on the lookout for new problems while solving old problems. In the deep south, beans, yard-long (asparagus) beans, and cowpeas can succumb to heat, nematodes, rust, bacterial spots, and other pathogens and pests. Senna (tall) and Partridge pea can provide “chop-and-drop” organic matter as sunnhemp does. Sunn Hemp can host foliar pathogens (some possibly seed-borne), in Florida, and does not reliably form nitrogen-fixing nodules on the roots, even when inoculated. Even so, it is useful as a fast warm season green manure cover.

The flower Gaillardia (blanket flower) is a quick-to-compost, chop and drop option for late winter to late spring, It decomposes quickly, and can provide a quick green manure. Gaillardia is nematode-resistant, great for beneficials and pollinators, but is susceptible to some foliar pathogens later in the season. You can sow Gaillardia in August, or even later in fall for early spring flowering.

Due to climate change, and the more year-round activity of nematodes, pathogens, and pests in Florida, they’ve been including more nematode-resistant grasses into their rotations. We all need to be thinking more about warmer-climate options, as climate change continues to push pathogens and pests farther north, earlier each year.

Winter hoophouse growing

 

Hoophouse Yukina savoy at the end of November.
Photo Ethan Hirsh

Last week I wrote about Winter Preparations for Vegetable Gardens. For those with a hoophouse, here are some notes on all the work we can do to grow winter crops there! For those without a hoophouse as yet, scroll to the end for Twenty Benefits of Having a Hoophouse

First, a roundup of previous blogposts on winter hoophouse topics.

Planning winter hoophouse crops includes a description of how we do our hoophouse crop planning so we can maintain a crop rotation and still pack the beds fully with hardy crops.

Fall hoophouse bed prep and shadecloth removal includes spreading compost, broadforking, and a step-by-step guide to hoophouse fall bed prep.

Hoophouse fall bed prep Plans A-D and spider-webs includes some lovely spider photos and a short video of ballooning, as well as info about our first-planted winter crops.

Hoophouse bed broadforked to loosen up slumped soil. I’m happy to say our soil structure has improved in the 18 years since this photo was taken!
Photo Pam Dawling

Young greens in the hoophouse

After the set-backs with our winter hoophouse greens transplants that I wrote about in Hoophouse fall bed prep Plans A-D and spider-webs, we worked really hard and got the whole house planted up. Most of the transplants have recovered from their transplant shock (wilting each day), during the cloudy weather we had.

The new seedlings are coming up fast and calling on us to thin them. We ended up not needing so many of the Plan D plug flat plants, but we’ve kept them for now “in case” .

Plan D: Winstrip seed flats in our hoophouse on Oct 16, a late attempt to catch up!
Photo Pam Dawling

Ultimately if we don’t need them, they’ll go in a salad mix. I wrote about Making baby salad mix last year. The past two days I have been able to harvest a mix in the hoophouse. The ingredient we are shortest of is lettuce. My first mix was spinach, Bulls Blood beet leaves, a few leaves of Tokyo Bekana, Bright Lights chard, Scarlet Frills, Ruby Streaks and Golden Frills, and a handful of lettuce leaves Red Tinged Winter is growing fastest, of all the varieties we planted this year.

Sowing hoophouse winter crops includes some discussion of the tools we like; pre-sprouting spinach seed and growing multi-leaf lettuce.

What’s growing in the hoophouse; reading; planning for winter is an October view of crops.

Frilly Mustards in our Winter Hoophouse is exactly what it sounds like. Four sowings, six varieties. All delicious.

Making baby salad mix includes a discussion of ingredients and methods, balancing nutrition, color, shape and loft.

Young green Panisse and red Revolution lettuce in our hoophouse in November.
Photo Pam Dawling

Cold-tolerant lettuce and the rest, our January 2018 assessment of the varieties we grew that winter and which survived the unusually cold spell we had. Includes sad photos of the casualties!

Also see my Mother Earth News blogpost from August 2018 Grow Great Lettuce in Winter

———————————————————–

Hoophouse seedlings growing outdoors under insect netting. Starting transplants outdoors helps the rotation by reducing the time the crop is growing in the hoophouse
Photo Pam Dawling

Do you value crop rotation in your hoophouse?

In the winter 2019-2020, 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.”


Doing a spot of research today, I find that Heterorhabditis bacteriaphora, (Hb nematodes) a beneficial nematode fromArbico Organics will attack flea beetles. also known as NemaSeek, and sold separately. This is the wrong time of year for introducing nematodes in most of the US. They need warm weather to thrive.

Another suggestion from Arbico is BotaniGard Maxx & other B. bassiana sprays, which infect and kill adult flea beetles. Repeat applications as needed throughout the growing season.

Kaolin clay (Surround) is another possibility.

Also see Harvest to Table on the topic of dealing with flea beetles

———————————————————–

View through the hoophouse doors in December.
Photo Kathleen Slattery

Add a hoophouse to your food production

For those of you wistfully thinking about a hoophouse, let me help you a step closer to having one next year! Sales of my Year-Round Hoophouse book are doing well, which suggests to me that quite a few gardeners and growers are thinking in this direction.

Twenty Benefits of Having a Hoophouse

  1. An extended growing season because plants are protected from cold weather.
  2. Faster growth and higher total yields.
  3. Beautiful unblemished crops not battered by the elements.
  4. Fewer foliar diseases because the leaves can stay dry.
  5. Crop survival at lower temperatures in the hoophouse than is possible outdoors.
  6. Better crop recovery in winter due to warm sunny days following the cold nights.
  7. Some protection from deer and other pests large and small.
  8. Soil temperature stays above 50F (10C) in zone 6b. Warm soil = faster cold weather growth.
  9. Higher proportion of usable crops – more food, higher sales dollars.
  10. Diverse crop portfolio – grow crops that wouldn’t succeed outdoors in your climate.
  11. Harvest whenever you need the crops, even during pouring rain!
  12. Wonderful working conditions – no need for gloves and hats; take off your coat.
  13. A food garden on a manageable scale.
  14. A place to enjoy practicing intensive food production.
  15. The chance to have an area completely free of weeds – new weed seed doesn’t blow in.
  16. No need to work with heavy machinery.
  17. Much better value for producing crops (per dollar invested) than a heated greenhouse.
  18. Can be constructed by generally-handy people. Specialists are not needed.
  19. NRCS grants are available for some hoophouses. Natural Resources Conservation Service, Environmental Quality Incentives Program, High Tunnel System Initiative.
  20. Ecological energy use. The embodied energy of the plastic is less than the energy that would be used to ship similar produce from somewhere warmer (Eliot Coleman, Four Season Harvest). Another study found this was not true for smaller (9 x 12 m) hoophouses – although the economic incentive for growers is still true, there is no energy efficiency advantage to the planet. Smaller carbon footprint: shipping 1 kg lettuce has 4.3 times the CO2 footprint of locally grown hoophouse lettuce. Plawecki, R., Pirog, R., Montri, A., & Hamm, M. (2014). Comparative carbon footprint assessment of winter lettuce production in two climatic zones for Midwestern market. Renewable Agriculture and Food Systems, 29(4), 310-318. doi:10.1017/S1742170513000161.
September sown White Russian kale (transplanted in October).
Photo Wren Vile

———————————————————–

Know your climate

WeatherSpark climate summary for Louisa, Virginia. Go to the website to click for more information

The WeatherSpark website provides “The Typical Weather Anywhere on Earth”. Enter your nearest town or airport and you get clearly explained info with fascinating graphics of how the weather goes over the year in your locality. Note this is not a forecast site, it’s about average weather for each place. Useful to people who’ve recently moved and want to know what to expect this winter, or to new gardeners who haven’t paid so much attention previously. Or to those who want to check their assumptions (I really thought the wind was out of the west more of the time than records say). There are charts of high and low temperature, temperature by the hour each month, cloud cover, daily chance of precipitation (both rainfall and snowfall), hours of daylight, humidity, wind speed and direction and solar energy. A big help in making wise decisions. I know that climate change is going to cause havoc with averages, and we’ll need to learn to become better weather forecasters individually, and to use soil temperature and other metrics to decide when to plant. This website explains things well.

———————————————————–

Winter gives a time for most of us to ponder success, failure, and possibilities for doing things differently.

 

Young greens in the hoophouse, nematodes, upcoming events

Young senposai transplant in our hoophouse.
Photo Pam Dawling

After the set-backs with our winter hoophouse greens  transplants that I wrote about last week, we worked really hard and got the whole house planted up. Most of the transplants have recovered from their transplant shock (wilting each day), during the cloudy weather we had.

The new seedlings are coming up fast and calling on us to thin them. We ended up not needing so many of the Plan D plug flat plants, but we’ve kept them for now “in case” .

Young Tokyo bekana transplant in our hoophouse .
Photo Pam Dawling

Ultimately if we don’t need them, they’ll go in a salad mix. I wrote about making salad mix last year. The past two days I have been able to harvest a mix in the hoophouse. The ingredient we are shortest of is lettuce. My first mix was spinach, Bulls Blood beet leaves, a few leaves of Tokyo Bekana, Bright Lights chard, Scarlet Frills, Ruby Streaks and Golden Frills, and a handful of lettuce leaves. Red Tinged Winter is growing fastest, of all the varieties we planted this year.

Ruby Streaks transplant in our hoophouse. Compare with Scarlet Frills below.
Photo Pam Dawling
Golden Frills mustard transplant in our hoophouse. I harvested a leaf for salad mix yesterday.
Photo Pam Dawling
Scarlet frills mustard in our hoophouse. Notice that this crop is frillier than Ruby Streaks.
Photo Pam Dawling

The mix I made today had fewer ingredients. I left the frilly mustards, the lettuces and the Tokyo bekana alone to grow some more. I used Bulls Blood beets, spinach, tatsoi outer leaves and a few Bright Lights chard leaves and stems.

Cucumber roots with nematodes (see circles).
Photo Pam Dawling

I have a new Mother Earth News blogpost, about the nematodes in our hoophouse. And I’m preparing a new slide show for the Carolina Farm Stewardship Association conference. See my Events page for details

For those of you on other social media, here are their handles and links (use the hashtag #CFSAC2018).

This week we will be popping garlic for planting and having our Annual Garden Crop Review meeting. Next week I’ll tell you more about garlic planting as part of the Alliums for November post.

Popping garlic cloves in preparation for planting
Photo credit Southern Exposure Seed Exchange