What are these abnormal growths on my spruce tree?

Galls are abnormal plant growths caused by insects, mites, nematodes, viruses and bacteria. There are many types of galls that can affect various parts of trees, such as leaves, stems, twigs, flowers and buds. Most galls are not harmful, but some types can be very damaging after repeated attack. Of concern are spruce gall adelgids and spruce gall midges. Large numbers of galls for consecutive years can cause spruce branches to become very thin and can even kill the branches.

The spruce gall adelgid group consists of the Eastern spruce gall adelgid and the Cooley spruce gall adelgid, both of which cause pineapple-shaped growths near the ends of branches. The Spruce gall midge causes cylindrical shaped growths at the ends of branches.  

These insects are all slightly different, but affect trees the same way. The feeding of newly hatched insects in spring stimulates plant cells to form a gall around them. Adults emerge from the galls late summer through early fall to reproduce and are very tiny winged insects.

Spruce gall midges causing deformity at branch tips

Here’s what we can do

Shadywood Tree Experts can help maintain your spruce trees with the use of proper pest diagnosis, systemic insecticide applications and annual fertilization. When you sign up for plant health care from Shadywood, we administer the recommended protocols for disease prevention control to keep your trees healthy. With each visit, our arborists assess trees for overall health.

Additional things you can do to maintain the health of your trees

Water trees regularly using a hose or small sprinkler for at least an hour every one to two weeks if there has not been adequate rainfall. Avoid spraying spruce needles directly as excessive moisture can promote fungal diseases. Mulch root systems when possible, using natural wood chips to protect the trunk, condition and improve the soil, and to conserve soil moisture.  If you see anything that doesn’t look right, have your trees inspected by one of Shadywood Tree Experts International Society of Arboriculture Certified Arborists.