Hackberry Psyllid, The Tiny “Gnat” Invading Homes
It is rare to find a hackberry tree without round growths on the underside of the leaves. These bumps, or galls, are the result of a tiny insect known as the hackberry psyllid. Hackberry is the only known host of this pest.
The adults of these insects are tiny and resemble miniature cicadas. They are dark reddish-brown with mottled wings. Most emerge from the galls during warm days in September and are very annoying as they gather around window screens seeking entry into the house. They are tiny enough to crawl through the openings in most screens. In the spring, the adults become active about the time the leaf buds open. The female lays her eggs on the underside of the developing leaves. Egg hatch occurs in 7 to 10 days, and the young nymphs begin to feed immediately. The leaf reacts to the feeding by producing a pouch or gall that entirely encloses the nymph.
Control is difficult. Adults that invade homes can be collected by using a vacuum sweeper but the bag should be discarded or the adults will escape. Since these insects do not seriously affect the vitality of the hackberry tree, control is usually not recommended. (Ward Upham)