Blue spruce with damage from spruce gall adelgids
A few years ago I planted 3 small blue spruce trees thinking that I would have sweet little Christmas trees adding interest to our winter landscape. The trees settled in and grew nicely and are now at least 10 feet high. Last year I noticed some brown lumps on my trees that I first mistook for cones. However, when I examined the trees more closely, I realized that something weird was happening. I clipped off a branch with the pseudo cones and visited Bayside Gardens, our local garden center, to see if they could identify the problem. Luckily Bayside has knowledgeable people and I was told that my trees had spruce gall adelgids.
They suggested that I use Bayer Advanced tree and shrub insect control to deal with the galls. The instructions for the insecticide explained that the insecticide is dissolved in water and moves down through the soil where it is absorbed by the roots. Once absorbed, it moves up through the tree or shrub providing year-long protection. This product even moves into new growth, protecting it as well. To get complete protection, the insecticide must distribute completely through the tree or shrub and depending on the size of the plant, this can take one week to three months for large trees. Rain cannot wash off this internal protection.
Various stages of spruce galls on our trees.
This all happened last year during a very hot spell of weather and I was reluctant to try something that was clearly such a drastic step. I thought that the cure might very well kill my trees especially since they were already stressed by the gall adelgids and the blistering hot weather, so I put off dealing with the problem!
This spring however, after looking at my damaged trees, I decided to try the cure. I read the directions again carefully and followed them exactly. The Bayside people were right, all the new growth has filled in and not a gall in sight!
Research
Most spruce trees are damaged by one of two species of gall forming adelgids (aphids); the Eastern spruce gall adelgid, A. abietis, and the Cooley spruce gall adelgid, A. cooleyi. These soft-bodied insects feed by sucking plant juices. They are small (1/16 inch) and not readily seen, but their feeding on young plant tissue causes the formation of obvious conelike growths called galls, which stunt and eventually kill the twigs. These insects are not a serious pest under forest conditions as they injure only a small portion of the foliage. At times, they disfigure ornamentals, and continued infestations may weaken trees and make them susceptible to attack by other insect pests and disease-producing organisms.