| There are a number of different insect and mites that cause galls to form. There are gall wasps, gall midges, gall adelgids, etc. Some eriophyid mites, which are pretty different than spider mites, can cause galls. Galls can look pretty wierd, but for the most part, their impact on the plant is minimal. They are mostly a cosmetic problem on ornamentals. We have, and you probably have it in Boise also, the cooley spruce gall adelgid which causes cone-like galls to form on the tips of spruce branches. Heavy infestations can cause the tree to look pretty ratty, but it has little effect on plant health. If the galls are unsightly, then just cut them off. If you want to see more galls, try this site. |
Here is a link that might be useful: British Plant Gall Society
