As you may have read in a previous post, root-knot nematodes recently became public enemy number one in the Hanbury House vegetable garden.  I was kind of depressed about it for a few days, struggling to find an Organic treatment to kill root knot nematodes in our garden.  Being a home gardener, especially an organic one, there are few options for dealing with nematodes in the soil.

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Organic Treatments for Root Knot Nematodes

Heat It Up

One of the most commonly recommended Organic methods to eliminate root-knot nematodes is solarizing the soil, covering the area with clear tearproof/ uv protective plastic for 6 weeks to allow the soil to reach 120 degrees for an extended period.  The area has to be in full sun for it to work.  However, soil solarization doesn’t just kill root-knot nematodes; it will also kill all beneficial nematodes, fungi, bacteria, and pretty much everything else alive in the top inches of the soil, good or bad. Heat and solarization are sort of nuclear options for treatment.

My particular veggie bed is only in full sun a few months out of the year, in the height of summer.  I am patient and could wait until then, but according to what I have read in some master gardening publications, solarizing is less effective near the coast where summer temperatures don’t get sufficiently high.  Our summertime highs are rarely over 80 or 85 degrees.  Great.  In all likelihood, it will not get hot enough to kill the little buggers in my coastal Southern California backyard, even in the height of summer.

Add More Nematodes?

Another option is to apply a commercially available product containing a type of predatory, beneficial nematode, Steinernema feltiae species.

Beneficial nematodes * are used by organic gardeners to combat a variety of garden pests, including root knot nematodes and beetle grubs in lawns. However, timing is important, and soil temperatures need to be above 60 degrees. Summer and fall are ideal seasons to apply them. In terms of products, there is no published research I could find by the University of California that lists this kind of product as effective.

Another Alternative

I need an effective organic treatment to kill root knot nematodes that works in the cooler seasons and in less than full sun situations.  A few of the management techniques recommended by UC ANR are better suited to a sunnier, more inland yard. After a bit of research and a suggestion from Patricia at the end of my other post, I decided I might as well give boiling water a try, especially since I will have to wait many months before trying solarizing.  In the past, I have managed to kill a few weeds with boiling water, and I am hoping it might also work against the root-knot nematodes in the garden. 

I came across a few university research papers that mention hot water above 120 degrees has been effective at eliminating nematodes on the root ends of bulbs, banana plant roots, hostas, and other greenhouse plant roots.  Hot water seems worth a shot.  Depending on the crop, the plant is left submerged for a different amount of time.  The publication about the banana plants said 30 seconds was sufficient to dip the ends of the plant and kill nematodes, but the one about bulbs said ten minutes.  I have no control over the time it takes to soak in, but if it starts out at boiling, by the time it cools down to 120, it should have had plenty of time to work and soak down in.  Boiling water is relatively cheap, non-toxic, and easily available, so the worst-case scenario would be it doesn’t kill the nematodes.

I spent the better part of my day going back and forth between the back garden and the stove, dumping gallon after gallon of hot boiling water on the veggie bed.  At any given point, I had three different pots and kettles going.  Now the bed looks like warm steamy mud.  I plan to go back in a few days and top the area off with homemade compost to help reintroduce some beneficial bacteria and microbes. I sure hope it all helps, and I will report back in the comments in a few months on whether or not boiling water was an effective way to kill root-knot nematoads in the garden.  Wish me luck!

For more detailed information on Soil Solarization, visit UC Agriculture and Natural Resource about Soil Solarization for Gardens & Landscapes.

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