A few years ago, I added worms from my worm bin to my indoor plants' pots.
My plants are currently infested with fungus gnats. How do I get rid of the
gnats without hurting my worms?
Houseplants are a fungus gnat paradise. They thrive in moist soil and feed
on decaying organic matter, algae, and fungi. Adult fungus gnats create a
nuisance, and the larvae damage plants by tunneling into succulent plant
stems and roots. Under normal circumstances, I'd recommend keeping the
affected plants' soil free of decaying leaves and allowing the top of the
soil to dry out between waterings. Dry soil kills larvae, reduces fungal
growth, and prevents adults from laying eggs.
But this situation calls for a more sophisticated plan of attack. Worms,
especially the composting worms you have added to your pots, do not do well
in dry soil, says Patrick Bohlen, Ph.D., director of research at the
MacArthur Agro-Ecology Research Center of Archbold Biological Station
in Lake Placid, Florida. "These worms sometimes migrate from containers
when conditions become less favorable, which means you could end up with
earthworms on your living room floor!"
Here are some strategies for keeping gnats out and worms in. Place yellow
sticky traps horizontally on the soil surface. They might not be pretty, but
they allow you to kill some adult gnats and monitor their populations. If
numbers are high, apply beneficial nematodes (Steinernema feltiae or S.
carpocapsae) that will attack the larvae. These nematodes are sold
commercially under the names Scanmask and Nemasys. Follow the application
instructions on the package. Oddly enough, your worms might even aid the
fight against gnats. "Earthworms have been shown to increase the dispersal
of Steinernema in some cases," says Dr. Bohlen.
Finally, there's always repotting your plants in sterile soil with less organic
matter. Of course, that means bye-bye worms; you'll have to relocate them.
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