Serviceberry Tree Problem

Asked June 25, 2020, 7:27 PM EDT

Good Evening,

Do you happen to know what these growths are on my serviceberry tree and, if they are harmful to the tree, how I can treat them? Thanks!

Livingston County Michigan

1 Response

These "bumps" are created by serviceberry galls. This is a rust/fungus that needs two hosts-a type of juniper and a plant in the rose family. Spores travel back and forth between the two hosts and you are seeing the results. Usually this will not kill a tree but continued infection could weaken it. If you have junipers in the area you may see this infection every year. Pruning out the galls may not be an option, as it appears the entire tree is affected. You can try removing the other host (a juniper of some kind).

The bumps are called galls and are created by either a midge or a wasp that has laid its eggs on the leaf. When hatched the tiny insects suck juices from the leaves. The leaves produce leaf tissue that covers the developing larvae; hence the "bumps. The galls effectively shield the insects from insecticides. Therefore, we do not recommend the application of insecticides.

If you look around, the leaves and stems of native trees and shrubs are frequently covered in galls of all sorts, sizes and colors, but they normally do not affect the health of the plant unless the number of galls is excessive. In your photos, I do see a fair amount of green leaf tissue so the plant should be able to sustain itself,

I can't guaranty that your shrubs won't exhibit galls in the future. However, your shrubs would be better able to take such an infestation if they are well-maintained and not competing for water and nutrients with grasses and weeds and all their cultural needs are met.