Insects on Hackberry Trees

Hackberry nipple gall maker Pachypsylla celtidismamma is an insect pest of hackberry trees creating bumps on the underside of the leaves, also known as galls. Nipple galls are common ailments of various trees in the landscape and can be caused by a few different insects. This specific gall is caused by a psyllid on hackberry trees. Most galls will be aesthetically displeasing in nature, but if severe enough can impede photosynthesis. Galls are generally created by a reaction within the plant tissue due to feeding from the immature insect (nymph). This reaction then causes a proliferation of growth which will encase and protect the nymph until maturity.


• Numerous galls form on the underside of leaves.

• Early leaf drop can occur on heavily infested trees.


The immature nymphs will hatch in the spring as the new leaves unfold and will begin feeding. This feeding causes an abnormal growth within the leaf tissue, which then encases the insect and protects it while it feeds and grows. The nymph then emerges as an adult in September where it will overwinter in leaf litter or bark crevices. The adults emerge in the spring and will lay eggs where the life cycle will start over again. 

 What To Do

Your arborist can make a couple of different recommendations based on the severity of the issue, and what time of the year they see the tree. One option will be to use insecticide sprays in the spring when the leaves emerge to target any of the nymphs that are emerging. However, the timing for this pest can be tricky, and if the insect has fed it may still cause the reaction within the leaf tissue. The other option is to use a systemic insecticide that will make timing less of an issue. Depending on the product used, it can be applied in the fall or early spring. The key to this treatment is to get the product circulated in the tree before the insect starts feeding. Once you see galls on your tree, it is too late to treat that year. It is also important to note that treatment will not remove the galls from the leaves if treated after they have formed that year. Contact us today!