Xtremehorticulture

Earthworm Castings (Vermicompost) Suppresses Insects and Disease

Q. I was reading your blog about worm castings, the chitinase enzyme produced by worms and its ability to control insects. Chitinase has been proven to degrade the chitin that holds insect skeletons together. Chitin is necessary for strong insect exoskeletons. So, using worm castings in garden soils will control insects. Homemade worm castings from red wigglers in an earthworm bin. A. Scientists think this may be true about worm castings are vermicompost, but the research hasn’t linked everything together yet. Chitinase occurs in the soil because of earthworms but does this chitinase control insects? Is the soil transferring this chitinase to the plants? Some preliminary research claims it can. The research is going on right now to find out how much value chitinase has controlling problem insects in the garden. Insect pests controlled            Studies report that Vermicompost application suppressed 20 – 40% pest problems arising from aphids, mealybugs, cabbage white caterpillars on pepper, cabbage and tomato.             Gardens are filled with insects. There are good insects and there are bad insects. Can the effects from earthworms only kill the “bad bugs” or will it also kill the “good bugs”? This is why more research is needed.             This is a similar problem with some of the “organic” insect control chemicals. Soap sprays and oils don’t differentiate between “good bugs” and “bad bugs”. They kill them both. We have to rely on our knowledge about “good bugs” and “bad bugs” and how it might be applied to control only the “bad guys”.  Plant disease controlled             There is some evidence worm castings or Vermicompost inhibited some fungal diseases as well as some nematodes in field trials with pepper, tomatoes, strawberries and grapes. It is believed the reason is microbial antagonism. The same effects have been found in manure and compost applications. Sterilizing both of Verma compost, manure and compost removed these effects.              When only one plant disease was studied, the disease suppression was not as good when the Vermicompost was made from sewage sludge.

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Worm Castings and Insect Control

Q. What effect do worm castings have on beneficial insects? Are there any special instructions or precautions to be considered when using worm castings around fruit and vegetable plants?  A.  I had not heard of worm castings used as an insect repellent or an insecticide until you mentioned it and followed up with a web link to a worm farm. They mention chitinase being the “active ingredient” that has an effect on insects.The word chitinase implies that it is an enzyme which dissolves chitin, a primary component of the exoskeleton in insects. Red wigglers from our worm bin I had to do some digging on this subject because I knew very little about it. The claim by the worm farm is that worms produce chitinase and deposit it in the worm castings. This chitinase produced by worms has an effect on bugs. Let’s keep in mind that insect exoskeletons surround good bugs as well as bad bugs. So anything that targets bugs in general kills all bugs whether they are good or bad.  Personally, I think this is a pretty big stretch about the chitinase produced by worms. There has been quite a bit of research on the use of chitinase and developing synthetic chitinase for targeting insects for pest control. But to make the jump from the chitinase produced by earthworms reducing insect pests in the garden is a pretty big leap and one that I am not ready to take. The research is just not there to support this kind of claim. Let’s stick with something we do know. Worm castings are a great natural fertilizer and help to improve poor soils. I personally have red wigglers in a worm bin for digesting kitchen vegetable and fruit scraps.Like them a lot.

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