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hickory leaf gall

Q: What are these growths on my pignut hickory leaves?

Q:  What are these growths on my pignut hickory leaves?  I think they are insects and they are chewing my leaves.

A:  I appreciate you bringing in samples of the growths as this helped me identify the problem more easily. Actually, these growths are most likely an insect gall.  Galls are formed when the female insect places an egg in the leaf tissue and then the plant forms a protective coating around the egg.  The egg then goes through its normal growth stage from egg to larvae then pupae exits out of the gall as an adult. Generally, these galls cause few problems for the plant and in some instances, the galls support beneficial insects. I believe the chewing you are seeing on the leaf edges is caused instead by a caterpillar such as the eastern tent caterpillar. Eastern tent caterpillars can be seen in of our area in April – right now!  Just poke holes in the caterpillar webbing and the birds and wasps will take care of the caterpillars for you.