Hackberry gall psyllids (Pachypsylla spp.) are emerging from their galls in southwest Ohio and Joe Boggs noted that he's receiving reports of these "black gnats" invading homes. Psyllids are dusky-black gnat-like insects that resemble miniature cicadas. Their clear wings are mottled with black markings. Their small size (1/16" long) also allows them to squeeze through standard-sized window screens. The psyllids buzz-bombing behavior makes them an annoying house guest and they may occasionally bite!
Home invasions are typically blamed on the hackberry nipple leaf gall psyllid, P. celtidismamma. However, there are several other hackberry psyllids that will also practice a little breaking-and-entering including P. umbilicus that produces the round hackberry "button leaf galls; P. celtiphyllia that produces the descriptively named hackberry "flask galls" on leaves; and P. venusta that produces 1/4-1/2" diameter galls on hackberry leaf petioles.
These hackberry galls usually "mature" in late-August to early-September to release adult psyllids upon Ohio landscapes. The newly emerged adults immediately seek protected sites to spend the winter. They are attracted to radiating heat or lights, making homes located near infested hackberry trees a likely target of these nuisance pests. Large numbers of psyllids may be found huddled beneath window frames and door jams.
Unfortunately, there are a limited number of effective options for preventing hackberry psyllids from invading homes. While some insecticides are labeled for control of psyllids on hackberry, accomplishing both the required proper timing and thorough coverage to achieve control is problematic. Homeowners suffering annual home incursions may consider changing window screens to a smaller size. Short of cutting down offending hackberry trees, there is little else that can be done.