Attraction of Choristoneura rosaceana to pheromone blends in ratios produced in glands or emitted by females

Abstract

AbstractTrap captures of obliquebanded leafroller, Choristoneura rosaceana (Harris), to pheromone blends in ratios approximating those reported in pheromone glands and a novel blend based on a volatile headspace collection from live virgin females were evaluated in field experiments in Michigan apple orchards. In an initial field trapping study, pheromone lures composed of either a three‐ or four‐component blend approximation of the blend present in female pheromone glands at doses ranging from 0.1 to 20 mg/lure were compared. The four‐component blend was a combination of (Z)‐11‐tetradecenyl acetate (Z11‐14:Ac), (E)‐11‐tetradecenyl acetate (E11‐14:Ac), (Z)‐11‐tetradecenol (Z11‐14:OH) and (Z)‐11‐tetradecenal (Z11‐14:Al) in a ratio of 96.5:1.8:1.4:0.2, respectively, while the three‐component blend lacked Z11‐14:Al. Pheromone emissions by groups of virgin females and commercial lures were collected in the laboratory and analysed by gas chromatography. These data were used to formulate a new pheromone lure that was compared to a commercial lure in a second trapping study. In the first field study, traps baited with 10 mg pheromones or above captured significantly more moths than traps baited with 1 mg or less, regardless of the blend. Surprisingly, groups of virgin females only emitted two detectable pheromone components, Z11‐14:Ac and Z11‐14:OH in a ratio of 37:63, which was substantially different from the blends detected in pheromone glands in the literature. The newly formulated pheromone lure based on females’ emission was more than twice as attractive as the commercial lure which emitted a 74:5:21 three‐component blend of Z11‐14:Ac, E11‐14:Ac and Z11‐14:OH. Our results suggested that the actual pheromones released by females may not translate directly to the content of pheromone glands.