Gypsy Moth Management in Suburban Parks: Program Evaluation²

A specialized gypsy moth management program for urban parks was implemented in six state and county parks and the Beltsville Agricultural Research Center (BARC) in Maryland in 1990 and 1991. Decisions to treat with aerial applications of Bacillus thuringiensis Berliner (one or two applications) or diflubenzuron or to not treat were based on gypsy moth egg mass density, egg mass size, percentage of susceptible host trees, amount of previous defoliation, and the potential non-target effects of diflubenzuron. A total of 1025 and 1926 ha in the management program was treated with one and two applications of B. thuringiensis, respectively, and 1204 ha were left untreated. One block of 47 ha was treated with diflubenzuron. Larval mortality as a result of the treatments averaged 76 and 83% in areas treated with one and two applications of B. thuringiensis, respectively, and 87% in the area treated with diflubenzuron. Some noticeable defoliation occurred under all treatments. The greatest amount of defoliation (29% of total area) occurred in a management unit with an average initial egg mass density of 49,250/ha that was treated twice with B. thuringiensis. Comparisons with adjacent areas not included in the management program indicated that even when defoliation did occur, it was reduced both in severity and extent by the treatments. This evaluation of the gypsy moth management program that was developed to provide a high level of foliage protection in suburban parks indicated that a number of improvements can be made in the program. However, without more efficacious intervention tactics, the goal of preventing noticeable defoliation in any part of a management unit may not be achievable solely with biological agents where extremely high gypsy moth population densities are present.