News Briefs City working with CSU professor to combat elm tree predator insects The city of Boulder Parks and Recreation Forestry Division is currently working with Dr. Whitney Cranshaw, entomology professor at Colorado State University and his graduate student, Loretta Mannix, to determine the effectiveness of a natural predator against European elm scale on American elm trees in Chautauqua Park. The insect being tested is the green lacewing, a natural predator of soft-bodied insects such as aphids and scale insects. European elm scale is one of the most widespread and destructive scale insects in Colorado and affects mainly American elm trees.
Prolonged infestations weaken branches, often producing premature leaf yellowing and drop.
Heavy infestations cause dieback of twigs and branches. Increased deadwood increases the tree's probability of attack by the elm bark beetle and infection by Dutch elm disease. Green lacewings are native to the western United States. They are released in the egg stage in a water slurry and hatch into the larval feeding stage. Only the least toxic available pesticides are used and trunk and soil injections are used whenever possible to reduce pesticide drift.