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March 14, 2014

Hackberry Nipple Gall-making Psyllid

Timothy J Gibb, Department of Entomology, Purdue University

This is one of my favorite insects. Not because it is big or colorful or flashy or even very interesting really, but what I like about this insect is its name. I just love saying it. It has a certain poetry. I would have named one of my children after it, but their mother does not appreciate poetry.

Hackberry Nipple Gall-making Psyllid is just fun to say. The name also suggests that these are the cause the small, discolored nodes called nipple galls that are so common on the undersides of hackberry leaves.

Psyllids are a group of small insects called jumping plant lice, and the name fits. They are tiny, plentiful at times and they do jump when disturbed.

In the late fall adult Hackberry psyllids emerge from their galls and fly, sometimes congregating on windows and screens. They are often described as tiny black jumping insects and are quite small - small enough to actually pass through the mesh of many window screens. That is why homeowners report them as being a nuisance in the home. They also fly to windows again in the late winter or early spring when temperatures begin to warm.

Under a microscope Hackberry psyllids resemble a miniature cicada – large eyes and with wings held roof-like over the back.  They pass the winter as adults and lay eggs again during the spring time on the emerging leaves of hackberry trees. When the eggs hatch, the tiny nymphs act like other gall-making insects by causing the leaves to form the distinctively shaped gall that they are named after. The tiny nymphs live and grow inside this protective gall. As summer progresses, the leaves can sometimes be covered with them.

These are not a serious pest of hackberry trees because the galls, although very conspicuous, do very little damage to the leaf.  Hackberry psyllids are mostly considered to be a nuisance pest when they get into homes.

Chemical treatments are seldom warranted. To prevent them from entering the home simply close the windows during the short period of time when they are active.  Alternatively, you may go to the hardware store and ask for window screens with a small enough mesh to exclude Hackberry nipple-gall making psylids.  I’m sure that even if the clerk has no idea what you are talking about you will sound smarter just for saying it.

Click image to enlarge

Insect on leaf

Insect near gall

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service