Odd lump-shaped galls on hickories are caused by an insect called the hickory pouch gall aphid. The gall began forming as the leaves developed. When the galls open up many of the damaged leaves fall. We see the heaviest infestations in trees isolated in landscapes. There seems to be far less activity in woodlots. It really is a cosmetic type of injury.

Extension Bulletin

 

 

 

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