Darkwinged fungus gnats, flies in the genera Lycoriella and Bradysia, are slender with comparatively long legs and antennae. They are grayish-black and about 1⁄8 inch long. These flies crawl about
Darkwinged fungus gnats, flies in the genera Lycoriella and Bradysia, are slender with comparatively long legs and antennae. They are grayish-black and about 1⁄8 inch long. These flies crawl about actively on growing medium or fly close to the soil surface. The eggs are yellowish-white and tiny. Darkwinged fungus gnat maggots have shiny black head capsules and white bodies. The last body segment is lobed and helps push the insect along. Mature larvae are about 1⁄4 inch long. Initially white, pupae become dark shortly before the adult emerges.
Darkwinged fungus gnat maggots feed on the roots of alfalfa, carnations, clover, corn, cucumbers, Easter lilies, geraniums, lettuce, nasturtium, peppers, poinsettias, potatoes, soybeans, wheat, and organic matter throughout the United States. Damage first becomes apparent when plants lose their healthy appearance and wilt. Darkwinged fungus gnat adults are usually noticed before injury caused by the maggots is apparent.
Darkwinged fungus gnat maggots are important pests in some greenhouses and mushroom cellars. Besides the adult nuisance factor, heavy larval populations can damage roots and enter tender stems at soil level. They are also pests of house plants. Several of these flies are of economic concern. In greenhouses, darkwinged fungus gnats are generally most abundant in the winter and spring. Adults and larvae inhabit moist, shady areas. Adults live about 1 week, during which time each female deposits 100 to 150 eggs. They are laid in strings of 3 to 40 on soil, usually near stems of plants. They hatch within 4 days in the greenhouse. There is a tendency for the progeny of each female to be all one gender.
The larvae begin feeding on the root hairs and roots usually in the upper two inches of medium, working their way up the plant and into the stem. However, they also feed on any organic matter in the soil. Being somewhat gregarious, the larvae often form clusters in the soil. They mature in about 14 days, after which they construct a pupal case in the soil made of silk and debris. The pupal stage lasts about 3.5 days. Adults are weak fliers, but they run rapidly on the soil surface.
In turf growing in high organic soils and areas of heavy thatch, darkwinged fungus gnats are occasionally seen in high numbers especially following wet periods. Adjacent natural areas and mulched beds may contribute to the situation. If a large number of eggs