CHEMICAL ECOLOGY Comparison of Female Attractiveness and Male Response Among Populations of Choristoneura rosaceana (Harris) in Western and Eastern U.S. Apple Orchards

Female obliquebanded leafrollers, Choristoneura rosaceana (Harris), collected from Oregon,Michigan, andNewYorkwere deployed in delta traps inMichigan apple orchards to compare their relative attractiveness to Michigan males of the same species. Females originating from Oregon attracted more males than females originating from New York during both generations of leafroller ßight in Michigan. Also, females from Oregon attracted more males in Michigan than did “native” Michigan females during the Þrst generation of ßight. Analysis of gland extracts from the three populations revealed signiÞcantly more of each pheromone component in females originating from Oregon (approximately nine-fold more pheromone per female overall) than those from Michigan. However, therewereno signiÞcantdifferences in the relative amounts of eachpheromonecomponent between Oregon and Michigan females. A 100:4:5:2 blend of Z11Ð14:OAc, E11Ð14:OAc, Z11Ð14:OH, and Z11Ð14:Ald was optimal for catching males in Michigan with no added or detrimental effect of Z11Ð14:Ald, conÞrming previous studies. However, 100:1 ratios of Z11Ð14:OAc relative to either E11Ð14:OAc or Z11Ð14:OH (also containing 2% Z11Ð14:Ald) captured more males in Oregon apple orchards compared with 100:4 and 100:10 ratios of Z11Ð14:OAc relative to either E11Ð14:OAc or Z11Ð14:OH. Addition of increasing amounts of Z11Ð14:Ald relative to Z11Ð14:OAc (range, 0Ð8:100) into a blend also containing 4% E11Ð14:OAc and 5% Z11Ð14:OH increased male catch in Oregon but not in Michigan. Our results suggest that pheromone blend quantity rather than blend quality may explain greater attractiveness of western compared with eastern female C. rosaceana to males in Michigan. Also, an optimized generic blend for monitoring male C. rosaceana across North America should contain Z11Ð14:Ald as has been previously shown, but should not exceed 4:100 ratios of both E11Ð14:OAc and Z11Ð14:OH relative to Z11Ð14:OAc for optimized catch of males in the western United States.