Those small gray flies in the yard and on the shrubs, flowers and vegetables are mostly seedcorn maggot flies. This field crop pest was very common this spring and caused damage to an estimated 100,000 acres of corn. The seed-damaging maggot stage lives in damp, high organic matter soil until growth is completed and the adult flies emerge.
The adult flies are harmless but are often present in such abundance as to attract attention. No control is necessary.
Part of the reason seedcorn maggot flies attract attention is their method of death. A large portion of the flies die as a result of a fungus that invades their bodies. Many of the infected flies die after landing and attaching to the foliage of ornamental plants. The dead flies, stuck to the plants, are obvious to homeowners and landscapers inspecting plants for signs of trouble. Thus, the flies are blamed for any and all symptoms on the plants, but of course, did not feed on the plants or cause any of the holes, spots or discolorations that may be present. To repeat, no treatment is warranted to control harmless flies that are already dead.
This article originally appeared in the June 8, 1994 issue, p. 85.