I have been receiving calls from longtime residents complaining about “tiny black gnats” that they have never seen before. Correctly identified as hackberry psyllids, these fall pests are making an encore appearance this spring.

The tiny bugs, sometimes called “jumping plant lice,” resemble miniature cicadas. On warm afternoons, the outdoor air fills with swarms as they gather on exterior sunny surfaces, cluster on window screens, accumulate on freshly painted surfaces and invade homes through open windows and doors.

Adult psyllids are 1/8-inch-long dark-colored insects with four transparent wings, prominent eyes and a body that tapers from front to rear. They overwinter wherever they can find shelter, such as in buildings, tree bark crevices and under fallen leaves.

The larvae develop on hackberry leaves during the spring and cause bumps, called nipple galls, to form. Adults reach maturity and emerge from the galls in the fall just before the leaves drop. The trees are not damaged by the galls or the adults.

Spraying the trees to prevent an infestation would seem to be the best method for control, and now is the time to think about doing that.

Insecticides need to be applied just after the leaf buds start to grow. Adults congregate on developing leaves to lay eggs and begin the cycle again. Spraying the trees soon after the adults are observed will help to prevent the nymphs from becoming enclosed in the gall tissue.

Generally, begin spraying 10 to 14 days after adults start to appear. Products such as Orthene and Cyfluthrin are labeled for this purpose.

To help control current populations, spray infested exterior surfaces. Residual sprays to consider include diazinon, Baygon and Cyfluthrin. The applications should be reapplied after a few days to maintain control. These insecticides may temporarily reduce the number of psyllids, but more may return as they come out of winter hiding.

Indoor control is more restrictive. Look for ready-to-use aerosols labeled for indoor control of flying insects. Direct the spray to areas of the home where insects are gathering.

Because psyllids are more interested in the hackberry leaves than your home, their numbers should drop the later we get into the season.

 Bruce Chladny is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him at 843-7058 from 8 a.m. to 5 p.m. weekdays.