Control march flies biologically
March flies are fly-like, up to 1 cm in size, dark, heavily hairy mosquitoes that appear in larger swarms in spring.
They form a family of their own within the bipeds. They belong to the mosquitoes, but do not bite.
The garden hair gnat (lat. Bibio hortulans) and the March gnat (lat. Bibio marci), also called the St. Mark's hair gnat, are frequently encountered here because they swarm especially often around St. Mark's Day, April 25.
The march flies are flower visitors and perform an important task in the pollination of early-blossoming fruit trees. Their larvae feed on dead plant remains and are thus important humus builders.
However, when they occur en masse, the larvae can become pests, namely when they begin to feed on the roots of living plants.
How do I recognize the larvae of the hair fly?
The young larvae appear in summer, in the first larval stage they are colorless and heavily hairy.
In the other three larval stages they become earthy brown and leathery, form spiny appendages, and bear a shiny chitinized head capsule. Depending on the species, they can grow up to 15 mm long. They like a lot of moisture and sufficient humus and live gregariously together in the upper soil layers.
Life cycle of the hair fly
Retreat of the larvae into the soil to overwinter.
In spring, the 4th larval stage (L4) develops.
Pupation for about 3 weeks in the soil.
Hatching of hair flies and flight in swarms (March- May).
Mating in the air and on the ground, life span of the mosquito about 10 days.
Egg-laying in late spring in humus-rich soil.
Larvae hatch after 35-40 days.
In fall, mass emergence of larval stages L1-L3 near the soil surface.
Damage caused by the larvae of the march fly
Normally, the larvae are very useful as they convert dead plant debris into valuable humus.
However, during mass emergence or even drought, the 4th larval stage larvae can cause significant damage after overwintering in the spring. They then feed on the roots of living plants in the upper layers of soil (up to 10 cm).
Larval stages L1-L3, which appear in the fall, do not yet cause visible damage.
Which plants are attacked by hair fly larvae?
In grasses, either the roots or the root collar are damaged by larval feeding. Unsightly staining of lawns is the result. In addition, the turf can be destroyed by pecking birds looking for the tasty larvae.
Many different plant species of agricultural and horticultural crops can also be damaged, e.g. sugar beets, cereals, potatoes or tomatoes by larval feeding on the living rootstocks.
Control march fly larvae with beneficial nematodes
Nematodes are tiny, filamentous soil organisms about 0.6mm long. They are natural enemies of hair gnat larvae. The nematode species Steinernema feltiae specializes in, among other things, hair fly larvae and can use them for its own feeding and reproduction.
Which larval stages are susceptible to nematodes?
The first to third larval stage (L1-L3) in April/May.