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Monday, February 22, 2016

Beneficial Nematodes and Diatomaceous Earth

Q. Will the diatomaceous earth I have used in my garden and around fruit trees kill beneficial nematodes?

A. Diatomaceous earth has the same effect on beneficial nematodes as any other nematode. I don’t know of any solid research that shows diatomaceous earth will reduce nematode populations. You might be wasting your money.
When nematodes are damaging plants, most recommendations are to mix compost into the soils to reduce nematodes populations and encourage more rapid growth. Some fruit trees such as stone fruits are grown on rootstocks, such as Nemaguard©, that are somewhat resistant to nematodes.

Some sources will tell you to grow varieties of vegetables resistant to nematodes, reduce nematode populations periodically using a technique called “soil solarization” or abandon the spot. I wish they were easy to control but they are not.


  1. My parents in Florida say they kill nematodes off by covering the area with black tarp and letting the sun bake them dead. Apparently this is common practice there, ever hear of it?

    1. Yes, a very similar technique is called soil solarization but uses clear plastic instead of black plastic. The black plastic is not as effective as clear plastic. It is a temporary solution because it reduces or kills off a portion of the nematode population but not 100%. This reduction in numbers allows you to grow for a short period of time until the populations increase from those remaining. You can read more about it at http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74145.html