DEVELOPMENT OF INTEGRATED PEST-MANAGEMENT PROGRAMS IN URBAN FORESTS -THE ELM LEAF BEETLE (XANTHOGALERUCA-LUTEOLA (MULLER)) IN CALIFORNIA, USA

The elm leaf beetle (ELB) causes severe damage to California's elms. T he goal was to develop a management system based on long-term populati on monitoring for decision making, and environmentally sound control m ethods. English and Siberian elms with ELB populations in 25 locations from the northeast to the central coast of California were sampled fr om 1985 to 1990. Population monitoring has indicated that each ELB gen eration (two to three per season) varies unpredictably in its potentia l for causing foliage damage. Each generation needs to be sampled and decisions made for control measures most suitable for that generation. From the data base, we have developed a sampling system in which heat accumulation above 11-degrees-C at ELB sites, measured in degree-days , indicates when to sample and, if necessary, when to treat. Sampling elm branch terminals for the presence of ELB eggs during the limited t ime when egg laying is near its peak provides a cost-effective means o f predicting foliage damage, and thus of deciding whether control acti ons are necessary. Two control options compatible with ELB natural ene mies have been tested: trunk banding with Carbaryl and Bacillus thurin giensis foliar sprays. A number of strains of the egg parasitoid Tetra stichus gallerucae have been released and at least one strain has surv ived over winter. When the number of these parasitoids has increased s ufficiently, either through same season releases or from overwintering survival, they have exerted substantial control.