Food Grade Diatomaceous Earth and Worm Farming

When used properly, Food Grade Diatomaceous Earth (or FGDE) is an effective tool in the arsenal against insect activities.  We have had great success at eliminating many different kinds of pests related to worm farming including millipedes, flies and mites.  FGDE is composed of fossilized algae and is a microscopic crystalline powder with very specific modes of effectiveness against many different pests.

Specifics:

• Caterpillars - As a foliar spray, FGDE reduces their ability to feed and move
• Ants - When sprayed on surfaces, ants have trouble moving around above ground.  FGDE damages the exoskeletons of ants.
• Mites - As a dessicant, FGDE reduces tiny insects' ability to maintain internal moisture levels
• Spiders - FGDE reduces ambient insects that they use as food
• Flies - Although not normally effective against adults, FGDE breaks the reproductive cycle.  Flies lay their eggs, fly off, and that's the end of the story.

FGDE is food-safe and remains effective against sub-soil insect activities even after being mixed into castings.

Possible downsides are that beneficial insects and nematodes are also reduced when FGDE is utilized and that newly hatched worms may have trouble with FGDE until they grow larger.  Usually FGDE and beneficial organisms are utilized for similar purposes, so this is generally not a concern.  Additional testing is required to determine the exact effect of FGDE on infant worms, but research on forums has not provided any indication that it has any negative effects on composting worms at all.  Until testing is completed, I do not recommend saturating your bins or bedding with FGDE, but it is safe to use around composting worms and generally has no effect on them provided it isn't applied directly, in a dry form to the worms themselves.

Other points to consider:

• A little goes a long way - Too much is rarely any more effective then just enough.
• It is a microcrystaline dust and not something that should be breathed into your lungs on a regular basis (use less, apply with water)
• It often doesn't eliminate all insects, but it can significantly reduce populations and activities to a negligible level
• Insects are incapable of adapting to it
• Only use Food-Grade
• It is high in Silica (%89)
• It is water soluble, but it does have trouble remaining suspended in water (We just keep it shaking while applying)
• It doesn't break down.  It will remain persistent wherever you apply it.

Some of the articles that I have come across researching FGDE in worm farming have recommended a light dusting with it and some have even gone as far as to say that it loses effectiveness when it gets wet.  I disagree.  From my experience, it is best applied by mixing with water and spraying.  It remains effective when wet unless washed completely off.  Perhaps the problem is a lack of patience because insects don't respond immediately to it's application in any way, but over time, usually within a day or so, you will see a difference if applied properly.

References:

• Diatomaceous Earth - Wikipedia
• FGDE - Worm Farming Revealed