The small pods on the leaves of this hackberry tree are caused by the hackberry gall psyllid (pronounced sill-ids). Another name is “hackberry nipple gall maker”. Psyllids, also known as plant lice, are tiny insects that feed on sap. Most will feed exclusively on a specific tree or plant. The adult hackberry gall psyllid lays eggs in the spring, and when the egg hatches the young psyllid feeds on the leaves, which respond by developing a “gall” that surrounds the insect. The insect stays in the gall and continues to suck on tree sap for the rest of the summer. Not all species cause formation of a gall, and psyllids on established trees rarely cause anything more visual damage. There are over 100 species of psyllids in North America, most of which aren’t harmful to the host plant in moderate numbers.
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