GYPSY-MOTH MANAGEMENT IN SUBURBAN PARKS - PROGRAM-EVALUATION

A specialized gypsy moth management program for urban parks was implem ented in six state and county parks and the Beltsville Agricultural Re search Center (BARC) in Maryland in 1990 and 1991. Decisions to treat with aerial applications of Bacillus thuringiensis Berliner (one or tw o applications) or diflubenzuron or to not treat were based on gypsy m oth egg mass density, egg mass size, percentage of susceptible host tr ees, amount of previous defoliation, and the potential non-target effe cts of diflubenzuron. A total of 1025 and 1926 ha in the management pr ogram was treated with one and two applications of B. thuringiensis, r espectively, and 1204 ha were left untreated. One block of 47 ha was t reated with diflubenzuron. Larval mortality as a result of the treatme nts averaged 76 and 83% in areas treated with one and two applications of B. thuringiensis, respectively, and 87% in the area treated with d iflubenzuron. Some noticeable defoliation occurred under all treatment s. The greatest amount of defoliation (29% of total area) occurred in a management unit with an average initial egg mass density of 49,250/h a that was treated twice with B. thuringiensis. Comparisons with adjac ent areas not included in the management program indicated that even w hen defoliation did occur, it was reduced both in severity and extent by the treatments. This evaluation of the gypsy moth management progra m 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, t he goal of preventing noticeable defoliation in any part of a manageme nt unit may not be achievable solely with biological agents where extr emely high gypsy moth population densities are present.