Expect Midges and Gnats after Rains

‘Midge’ and ‘gnat’ are common names for many species of small, non-biting flies resembling mosquitoes. They can be nuisances following extend rainy periods. Large mating swarms often appear about dusk. Irritation comes when many of the small flies land on people or are inhaled. These gnats are attracted to light and large numbers can end up resting on exterior surfaces or enter homes or businesses. Gnats do not feed and only live for a few days; however, their survival is extended during cool, humid periods.

Figure 1. Gnats resemble mosquitoes but cannot bite. They can be a temporary nuisance after rains (Photo: Lee Townsend, UK).



There are no good ways to control these flies. Aerosol sprays containing pyrethrins will kill flies that are hit directly with spray particles. The impact is immediate but there is no extended control. Pyrethroid insecticides can be applied to surfaces where the insects are resting and can give some extended control.

Long term management of chronic gnat problems requires identifying and eliminating breeding sites, which commonly include seepage areas or standing water. The life cycle usually takes about 4 to 5 weeks, so there are several generations during the summer. Fortunately, problems with these insects are usually temporary and intermittent. Generally, nuisance problems disappear with the onset of dry weather.


By Lee Townsend, Extension Entomologist


Posted in Human Pests