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 galls horticulture

1 Response

Nipple galls are caused by the feeding of a small insect called a psyllid:
https://extension.entm.purdue.edu/publications/HN-86.pdf
http://www.dcconservation.com/Tips_Links/hackberry_nipple_gall.htm

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.