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Research Update: Does Pruning Trees Attract Insects?

July 18, 2006

You probably have heard or read the recommendation to avoid pruning trees and shrubs during particular times of the year to minimize attack from wood-boring insects. For example, we recommend to not prune white birch trees between May and August because the volatiles emitted from pruning wounds attract female bronze birch borers, which are active during this period. As such, this reduces the attractiveness of birch trees to egg-laying females. It has been reported that the incidence of Dutch elm disease is higher in areas where trees are pruned when the smaller European bark beetle (Scolytus multistriatus) is most active.

Research has shown this to be the case with elm trees and smaller European elm bark beetles. It was determined that pruning wounds of English and Siberian elms enhance the release of volatile attractants, thus increasing the response of smaller European elm bark beetles and assisting the beetles in locating breeding sites. As a result, the pruning of elm trees should be performed during late fall and winter when the beetles are less active.

Author: Raymond A. Cloyd


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