ALARM PHEROMONE SYSTEM OF THE WESTERN CONIFER SEED BUG, LEPTOGLOSSUS-OCCIDENTALIS

The alarm pheromones for adult and nymphal western conifer seed bugs, Leptoglossus occidentalis, were collected from the headspace volatiles of agitated bugs and from extracted adult thoraxes and nymphal abdome ns. Adult bugs secreted a blend from the metathoracic glands that cons isted of hexyl acetate, hexanal, hexanol, heptyl acetate, and octyl ac etate (ratio of 152:103:8:1.5:1). Nymphal alarm pheromone produced by the dorsal abdominal glands consisted of (E)-2-hexenal. Agitated adult s emitted similar to 24% of the pheromone contained within the glands, while nymphs released similar to 33% of their constitutive supply. Th e complete blend from both adults and nymphs, tested in a laboratory h eadspace bioassay, elicited a dispersal (or alarm) response in >70% of individuals tested. Nymphs in the field exposed to synthetic adult or nymphal pheromones, or a mixture of both, responded with >50% dispers ing. When single components were tested on adults reared under summer conditions in a forced-air one-way bioassay, hexanal and hexyl acetate , the major components of the secretion, were responsible for elicitin g the alarm response. Adults collected in the fall from the field were unresponsive to the tested blend, suggesting that adults seeking aggr egation sites in the fall become refractory to alarm pheromone stimuli that would cause aggregations to disperse. The weak dispersal respons es elicited in both adults and nymphs by either nymphal or adult phero mones are consistent with a tradeoff in the advantage gained by avoidi ng predation and the disadvantage of leaving a food source. Because of these weak responses, use of alarm pheromones as pest management tool s against L. occidentalis is unlikely.