A Giving Gardeners Plea: Dealing with Club Root (aka slime mold)

A Giving Gardener (who volunteers at several gardens) wanted to alert everyone to the challenge of club root. The gardener sent the pictures which we’ve uploaded and also shared research and experience with us. Susceptible crops include but are not limited to: rapeseed, mustards, brassicas, broccolis, the –chois, turnips, radishes, cauliflower, kale …

We also asked the broader community what they have tried in their gardens, and what was helpful.

Here’s pictures of infected and healthy roots, the Giving Gardener’s comments about the problem and some solutions that’ve been considered —

and some advice from other gardeners in the community :

Clubroot; Fungus Pasmodiophora Brassiecae, alias Clubfoot
Clubfoot is a fungus that resembles slime mold, which is soilborne. Clubfoot is spread by contaminated transplant and tools. It creates cyst/spores that can survive for years in the soil. The cyst lies dormant in the soil 6-12 years till a live host reappears.

The first signs of club foot are wilting during the day, and then yellowing leaves that die. The diseased plant is stunted and when dug up, there are deformities of the roots such as knots, clusters, and sometimes black diseased areas in turnips and radishes.

One web site I found says to dig up plants and sow Rye, after 2-3 weeks of germination till it into the soil, raise your pH to 7.2 mixing in Hydrated lime into it in fall. Improve your soil for drainage, continue to check pH balance. You can also “solarize” the area by putting down a clear plastic sheet(s), 1-2 mil is better than thicker sheets, between May-September to heat up the soil and it will kill the fungus if heated enough.

In seed growing, be sure your soil, trays and pots and any utensils use to work with them are sterile. If any of your equipment has been contaminated by clubfoot cyst, it will continue to contaminate the cruciferae, brassicaeae family. Throw contaminated tools out. There is nothing worse than losing a crop for the season and contaminating the patch for years. Check your transplants before selling, giving or planting them out.

In the patch, prevention is the best way. It seems 3-5 years is a popular number of years. In a small space, we could try for 3 years, making sure that you keep your soil to an optimum and watch how your plants are doing. Keep your soil pH between 6.5-6.8 by adding lime to the soil and when you plant your transplant, dig the hole, add a small handful of lime into the hole (to discourage clubfoot disease), mix lightly in the soil, put in the plant, cover and water.

ALWAYS check any transplants you grow or buy before putting in the ground.
DO NOT PUT in your compost, if it is infected it will spread throughout your patch or garden or create a new problem.

https://en.wikipedia.org/wiki/Clubroot
http://bonnieplants.com/growing/growing-cabbage/
http://vegetablemdonline.ppath.cornell.edu/factsheets/Crucifers_Clubroot.htm
And many years of reading about this fungus.
Jlyn’15

Here’s some additional advice from other gardeners in our community:

1. It’s good to try to prevent getting this stuff into your soil in the first place: but it’s transmitted by pots and flats and your own muddy boots, gloves and tools (even if you just put one down on an uninfected plot after it’s rested in an infected plot you’ve carried the stuff over) and by heavy rains and by compost. Even compost which has been hot enough may still harbor the slime mold in drier places in the compost. Having said that: apparently it also prefers heavier, wetter soils to lighter, more aerated ones. And common weeds – like the mustards and cresses – can carry it so even if you’ve been quite careful you could be defeated by the weeds.

Still, it is worth it to try to prevent infestation and many of these steps also help to control it once it is present. Here’s some steps that gardeners found helpful:

Clean your tools and boots; consciously work from “uninfected” towards infected places to avoid carrying it over.
If you see it in transplants: don’t plant them.
Practice crop rotation: “starve it out” before it becomes an obvious problem. (Keep a garden log and map to jog your memory.)
Use resistant varieties (SGGN plans to purchase resistant seed next year, if at all feasible.)

2. Strategy, strategy, strategy: Decrease the amount of it in the soil. IF you don’t grow there for quite a few years it can’t thrive and will be less of a problem – but still can be present for many years: one source said it could survive for up to 20 years.

The common strategies for decreasing it in the soil include:

• Starving it out (don’t grow susceptible crops; avoid brassicas for at least 4 years.)
• Increase the pH of the soil (to 8) by using lime or a source of lime such as wood ash (but be cautious that you don’t inadvertently create new problems by doing this such as soil contamination, a hostile environment for your other crops ….) Liming is expensive and actually pretty tricky to do right (see below). One gardener says to apply lime in October. Another says use a handful of wood ash when you plant. For those of us who need numbers:
Laura Matter with The Garden Hotline (Seattle Tilth) help@gardenhotline.org
www.gardenhotline.org says: “We know lime can affect how successful (or not) club root is in the soil. A higher pH can reduce the effect on your brassicas. The Royal Horticultural Society says: On acid soils, lime at the rate of 500g per sq m (15oz per sq yd), with lighter dressings of 270g per sq m (8oz per sq yd) in future years This is not a cure but a help.”
• Solarization (know that this will kill everything.) Reportedly this only gets the stuff that’s 3-4 inches deep so you’ll need to till and do it again ….
• Grow a “plant trap” which once infected you can throw away (arugula roots) or till and compost (a rye crop; till as soon as it sprouts.)
2. Help your plants to outgrow it: Older plants may not be as affected so use larger transplants; heap clean soil around the plant to encourage healthy roots.
3. Pull out affected plants (put them into the garbage not your compost)
4. Make the environment less attractive to slime mold — because healthy soil has healthy fungi that can decrease the load of the problem slime mold. Use a good uncontaminated (and quite possibly not home-made) compost to lighten the soil. Consider raised beds which drain better or replacing the soil in your beds.

Liming (or other steps to change the pH in your soil) is complicated. Here’s a start: www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs142p2_053252.pdf