Tree leaf gall

Asked July 22, 2017, 2:00 PM EDT

What causes gall (nipple like protrusions) on back of hackberry leaves? Is it preventable? Tree is approx 10' tall & this is second summer in our yard.

Stearns County Minnesota

1 Response

Nipple galls are caused by the feeding of a small insect called a psyllid:

Nipple galls do not harm the tree, so no control is necessary. You can reduce the number of psyllids by raking and burning the leaves in the fall.