Gnats and Springtails – Common Pests Following a Wet Spring

Gnats

Gnats are any of several species of small, non-biting flies. They appear suddenly, forming annoying swarms in the air as they mate. While they look like mosquitoes, these gnats cannot bite (Figure 1). Usually, they live for just a few days, and then disappear. Some are attracted to light and may be a nuisance, landing on people or entering homes or businesses.

Figure 1. Non-biting gnats. (Photo: Lee Townsend, UK)

Figure 1. Non-biting gnats. (Photo: Lee Townsend, UK)

The immature stages of gnats develop in standing water in pools, containers, ponds, clogged rain gutters, or in some cases, wet soil in seepage areas. Most feed on algae or decaying plant matter.

Management

  • Elimination of gnats (and other pests) usually is most effective when the breeding site can be located and eliminated. This provides a permanent solution to the problem, but it is not easy. The breeding sites can be hard to find and often there are not effective control alternatives, except to eliminate the water or moist areas, which may not be practical.
  • There are no good alternatives for control of the adults, other than some pressurized aerosol sprays containing pyrethrins. These are impractical for treating anything other than small areas. These products only kill insects that are directly hit by spray particles; there is no lasting or residual effect. More gnats will quickly enter the area after the spray has settled. The gnats rest on vegetation and in the grass during the day, so an application of a pyrethroid spray may reduce numbers somewhat. Fortunately, the problem usually is temporary since the insects live for just a few days.

Springtails

Springtails are small, wingless insects (Figure 2) that are very abundant in moist leaf litter or soils with high levels of organic matter. They can hop around like tiny fleas.

Figure 2. Springtail. (Photo by C. Judy)

Figure 2. Springtail. (Photo by C. Judy)

Springtails typically feed on decaying plant material or fungi that grow in humid areas. Springtail problems following rainy periods tend to result from accidental invasion from around foundations. The small insects can enter through gaps under exterior doors or windows or other openings. They can also enter homes via openings to crawlspaces. In some cases, springtails can live for some time in damp areas of houses and buildings that meet their moisture needs. These insects also can live in pots containing over-watered houseplants. Allowing the soil to dry out will usually eliminate them. Occasionally, they can infest greenhouses where they may nibble on plant root hairs or tender leaves.

Management

  • Springtails are not harmful but their presence in an area indicates moist conditions and high humidity that may come from things such as water leaks, condensation from sweaty pipes, or inadequately ventilated crawl spaces. These soil-dwelling insects also thrive following extended wet periods. In some cases, correcting moisture problems will end the infestation and the potential for more serious water or mold damage in a structure. Then, using a fan or dehumidifier to increase ventilation and to provide a drying effect in the home can be very effective in ending the problem.
  • Aerosol insecticides that are labeled for indoor insect control can be used to reduce springtails temporarily, but this does not correct the moisture or humidity problems that allow the insects to thrive.
  • Outside the home, remove excessive mulch and moist leaves, prune shrubbery and ground covers, and eliminate low, moist areas around the house foundation to permit proper air circulation. Remove wet, moldy wood or other moldy items.

 

By Lee Townsend, Extension Entomologist

 

 

Posted in Household Pests, Human Pests