Saturday, January 3, 2009

Fungus Gnats Fluttering Around

Picture of fungus gnat. Photo found at Texas A&M University:

Bringing plants indoors could result in another flying insect fluttering around inside, since these plants could have become infested with fungus gnats during the warmer weather. Adult fungus gnats are small, 1/8 to 1/10 inches in length, grayish black in color, have a slender body with long legs and antennae. They also are identified by the Y-shaped wing vein. Fungus gnats are usually weak fliers, so they tend to rest on foliage or growing media.
The female fungus gnats will lay tiny, oval semi-transparent eggs in moist organic debris. The fungus gnat eggs hatch into legless larvae that are white to clear in color, with shiny black heads. They eat organic mulch, compost, root hairs, and fungi. The larvae can damage roots of plants, which causes wilting, poor growth and loss of foliage. The flies then pupate in the soil within silk-like cocoons. The complete lifecycle from egg to adult occurs in around 4 weeks.

Some Suggestions for Control Measures:

1) Inspect plants before purchasing and use sterile potting soil.
2) Allow soil to dry for several days to kill some larvae, since over watering, poor drainage and water leaks can result in a large population of fungus gnats. If the top layer of the soil becomes dry, then the larvae will likely die and the females will be less likely to lay eggs in the soil.
3) Discard heavily infested plants to avoid infesting other plants.

Biological Control
1) Some predators of fungus gnat larvae include Steinernema spp. nematodes and Hypoaspis spp. mites that can be applied to the soil.
2) Bacillus thuringiensis israelensis (Bti) can be applied to the soil to control fungus gnat larvae.

Some Chemical Control Options
Larvae can be controlled by many chemicals, such as those containing azadirachtin and imidacloprid. Adult fungus gnats can be controlled by foliar treatments, such as those containing bifenthrin, permethrin, resmethrin, and neem oils.

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