The attraction of undesirable insects along with the honeydew mess and damage to painted surfaces caused by honeydew are factors which often motivate people to control aphids on shade trees. If compelled to spray these plants, use an alternative product such as insecticidal soap to reduce the impact on beneficial insects. Other products labeled for aphid control in trees and shrubs are listed on the back of E-296. The poplar bud gall mite causes cauliflower-like galls to form at leaf buds of cottonwoods and other poplars. These galls are dark green in color early in the season and turn brick red by late summer.
Old galls have a ridged and furrowed surface, are hard, and grayish in color.
Although trees are seldom killed, lower branches often become crooked, stunted, and are often killed. Continuous attack may weaken a tree, increasing its susceptibility to drought, frost, or other injuries. Some of the greatest damage caused by poplar bud gall mites is seen on hybrid poplars. There appears to be a wide range of susceptibility of poplars to the mite. When planting hybrid poplars in areas where the mite has a history of causing damage, use more resistant cultivars.