Elm Bark Beetle Mortality on Lab-Sprayed Bark Chips, 1981

Abstract

Abstract Suspended from the edge of a horizontally rotating 27 inch bicycle wheel, four 35 mm x 35 mm elm bark chips were sprayed with an insecticide during 1 pass before a compressed air paint spray gun beneath the wheel axle. The gun delivered 2.2 ml/sec and the wheel turned 4 rpm. This apparatus was in the opening of a laboratory evacuation hood. Bark chips, including some sapwood, had been cut with a band saw from 100 mm dia log disks from a recently felled tree. When each sprayed chip was nearly dry it was dropped into a 0.5 pt tapered Mason glass jar having a 100-mesh screen lid and the botton covered with a disk of paper towel. Beetles react abnormally on glass as compared with paper. The jar was placed in a randomized position on the first of 4 parallel lines on a laboratory table; the next jar was placed on the next line; etc. A draft of air from a household fan covered the table. The foregoing procedure was repeated for each insecticide. Sprays of all insecticides were agitated and buffered to pH 6. On each of the following 4 days a separate line of jars was infested with 25 beetles per jar from a laboratory culture of infested elm logs in 5 gal lard cans; each day represented 1 of 4 replicates. Moribund and dead beetles were counted after 24 hr. With poorer treatments this usually involved dissecting the chip to find the boring beetles. Results were subjected to a 2-way analysis of variance.