Boulder Vermicomposting

Questions: Plant diseases in feedstock and can worm cocoons drown?

November 15th, 2009

Melissa, a reader, asks:

Could you tell me what the likelihood of mature vermicast containing plant diseases originating in leaves used as feedstock? I know that properly produced worm tea suppresses/fights plant diseases when applied to plants. However, I read on line that Australian standards for vermicast require some degree of pasteurization of feedstocks for mature vermicast. I appreciate any help you can give me with this.

Also, can worm coccoons drown in worm tea?

Thanks.

Melissa, thanks for writing in!  I am afraid I don’t have any firm answers to either of your questions.

First off, as you know, worm composting does not reach the high temperatures that normal composting does.  That heat is what kills plant diseases.  While redworms have shown effectiveness in dealign with human pathogens, and vermicompost helped supress several plant diseases [PDF], I was unable to find anything directly attacking the problem you have: feedstock infected with a plant disease.  If I were looking to sell the vermicompost, or use it on food plants that would come in contact with it, I would make some first and getit tested for the particular disease that was in the feedstock.  Then, depending on that result, you could always start by hot composting the feedstock first.  (As an aside, here’s an interesting abstract showing the finished product of worm composting and hot composting end up with dramatically different types of bacteria populations.)

Second, I’m not sure whether or not worm cocoons can drown.  I found several references on the web to viable worm cocoons floating, but when I put a worm cocoon in water, it sank.  I found other conflicting references.  Again, in searching, I found some interesting facts (some worm cocoons can survive -8 degree celsius (-22 F) for 3 months, cocoons dehydrate at lower temperatures) but no authoritative studies on the survival characteristics of redworm cocoons.  Here’s a forum post from the author of “Worms Eat My Garbage” which indicates that cocoons are not hurt by water:

I have put dozens of cocoons in Chinese takeout condiment containers with non-chlorinated water covering them (to keep them from drying out). I watch daily to see if any baby worms have hatched overnight.

The safest course would be to sift cocoons out before you make worm tea, or perhaps skim off the bottom layer periodically, since hatched worms are known to die in 100% water environments.

These are both fascinating questions experiments; please let me know if you end up experiementing around either one.

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