Avid Trunk Injection as a Control for Elm Leaf Beetle, 1988

Ten Siberian elms along a street in Omaha, Nebr., were used in this test. The trees ranged (at 4.5 ft) from 6.5 to 18.5 inches diam and were approximately 25 ft tall. Trees were paired along the row into 5 replicates. An Avid treatment and an untreated control were assigned randomly within each replicate. The Avid treatment was applied by injecting 0.8 ml of Avid 0.15 EC (2.0% AI) into holes drilled into the trunk near the ground. The number of holes was determined by dividing the circumference of the trunk at 4.5 ft by 4. Each hole was one-quarter inch diam and approximately 1 inch deep. The holes were spaced evenly around the trunk. Treatments were applied and initial tree crown foliage ratings were made on 5 Jul, when considerable defoliation by the first generation of the elm leaf beetles had already occurred. Crown foliage ratings were made on a scale of 1 to 10, with 10 indicating no defoliation and 1 indicating very heavy defoliation. Posttreatment crown ratings were made on 24 Aug using the same 1-10 scale. Second- and third-instar larvae were collected on 15 Jul from neighboring untreated trees and placed in cages (10/cage) in the laboratory on foliage from the 10 test trees. Survival of the larvae in each cage was recorded on 18 Jul. For the previous 6 months, rainfall had been 26% below normal. From 1 Jul through 31 Aug, rainfall was 4.0 inches, 48% below normal.