Submitted to: Journal Of Arboriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 1994
Publication Date: N/A
Interpretive Summary: The gypsy moth is a serious pest of deciduous trees in forests, parks, and residential areas. While the aerial application of insecticides is the most effective and economical method for protecting trees in the forest, this approach is not always practical for individual trees. Ground-based applications of insecticides by a professional arborist or pest control operator are frequently used to protect trees in non-forest settings. Sticky trunk barriers are another gypsy moth control tactic that can be employed both by professionals and non-professionals. This study was conducted to evaluate the effectiveness of ground applications of three commonly-used insecticides, insecticidal soap, the bacterial product, Bacillus thuringiensis (B.t.), and the chemical, cyfluthrin, both alone and with trunk barriers. Insecticidal soap did not protect oak foliage from gypsy moth damage. Both B.t. and cyfluthrin provided good foliage protection. The trunk barriers reduced larval density and defoliation under all insecticide treatments and on unsprayed trees, but their effect was minimal on trees treated with B.t. or cyfluthrin. Information on the effectiveness of ground-applied insecticides and sticky trunk barriers should help homeowners and property managers decide what actions they should take to protect oak trees from gypsy moths.
Technical Abstract: The combined effects of ground-based insecticide applications using hydraulic equipment and sticky trunk barriers was tested on individual white oak, Quercus alba, trees under heavy gypsy moth, Lymantria dispar, pressure. The insecticides tested were insecticidal soap, Bacillus thuringiensis (B.t.), and cyfluthrin. The insecticidal soap had no effect on larval density or defoliation. One week after treatment with insecticides, the B.t. and cyfluthrin treatments reduced larval density from 500 larvae per m2 on unsprayed, unbanded trees to 180 and 30 larvae per m2, respectively. Defoliation exceeded 75% on unsprayed, unbanded trees and unbanded trees sprayed with soap, but remained below 25% on trees sprayed with B.t. or cyfluthrin. Trunk barriers reduced larval density and defoliation under all insecticide treatments and on unsprayed trees, but their effect was minimal on trees treated with B.t. or cyfluthrin. None of the treatments affected the total number of gypsy moth egg masses on treated trees. These results indicate that ground-based applications of both B.t. and cyfluthrin can provide good foliage protection, but that the use of trunk barriers with these treatments provides little or no added benefit.