Several arthropods reliably appear in force following a series of spring rains. For the most part, they are short-lived, so control measures are rarely needed.
Many species of non-biting gnats develop in moist decaying organic matter, temporary mud pools, and ponds. Hordes of adults can emerge suddenly. While they resemble mosquitoes, they lack the long beak of the closely-related blood feeders (Figure 1). Gnats live just long enough to mate and lay eggs. Their diet may be nectar, water droplets, or nothing at all. Large numbers may be attracted to lights so their nuisance value is intensified for a few days, then they die.
Elimination of gnats (and other pests) usually is most effective when breeding sites can be located and eliminated. This provides a permanent solution to the problem, but it is not easy. 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 must hit insects directly to kill them; 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.
These tiny insects can hop like fleas but, like the gnats above, they do not bite. Springtails are very abundant in moist leaf litter or soils with high levels of organic matter. 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 into crawlspaces. They can live indoors if a moisture problem provides the humidity and detritus (waste or debris) that they need.
Springtails are not harmful, but their presence in an area indicates moist conditions and high humidity. These conditions may come from moisture problems, 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, use of 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.
Pillbugs (including sowbugs, roly polys, and woodlice) are small armored creatures (Figure 5) that live in leaf litter, compost piles, or nearly any site that provides protection, humidity, and food in the form of dead wood or vegetation.
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 decaying items.
Hot, sunny conditions will drive slugs deep into the soil. Refer to the March 15, 2016 KPN article for additional details.
By Lee Townsend, Extension Entomologist