Got Gnats!!!

How to Deal With Fungus Gnats


Fungus gnats are those tiny hopping and flying insects that you see when
you water your houseplants and greenhouse plants. They are 1/32 to 1/50
inches with gray or black bodies and clear wings. Plants grown under cover
are most susceptible. The larvae feed on dead roots and leaves, but
sometimes feed on tender new roots.

The adults live about a week, but during that time they lay hundreds of
eggs in the soil of your potted plants. They particularly like damp soil
that is rich in organic matter. The eggs hatch in 4-6 days and for about
two weeks the larvae feed on plant roots and root hairs in the soil. This can
weaken the plants, causing leaves to suddenly wilt or turn yellow. Plants
may drop their leaves in severe infestations.

If you see fungus gnats flying around your plants, you can be sure there
are also larvae feeding on the roots. To monitor the fungus gnat population,
use yellow sticky traps placed horizontally near the plants. Yellow stickyt
traps are available at many garden centers. You can also place inch-long
pieces of raw potato on the soil surface. If fungus gnat larvae are in the
soil, they will migrate to the potato within four hours to begin feeding.
The larvae are 1/4 inch white-bodied maggots with black heads under and
on the potato piece.

Once you know your plants have fungus gnats, the adults can be killed
with any insecticide spray labeled for gnats or flying insects. Treating
the larvae in the soil is another matter. A soil drench is most effective
in killing the larvae. There are organic products available specifically for
killing fungus gnat larvae, including a form of Bt (Bacillus Thuringiensis
Berliner var. israelensis). Gnatrol is the brand name of one form of Bt
for fungus gnats. There are also parasitic nematodes that attack fungus
gnat larvae, although this is more useful for large-scale plantings. Neem
oil is also effective against fungus gnats.

Happy Gardening!

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