FACTORS AFFECTING CALLING BY FEMALE EASTERN SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

Abstract

Calling (extrusion of the sex pheromone-producing gland) by spruce budworm females follows a circadian rhythm regulated by the initiation of the photophase. At 2 °C 50% of the females call by 131/2 hr after "lights-on." Calling starts earlier at cooler temperatures. Females that have not been exposed to lights-on start calling as soon as darkness occurs. Virgin females are most attractive 3 to 4 days after emergence. Mated females call intermittently and are attractive but compete poorly with virgins. Once started, female budworm call continuously throughout the calling period, implying that their pheromone release rate is lower than if they called for short intervals only as in some other Lepidoptera. This may influence the quantities of synthetic pheromone required to disrupt mating behaviour. Calling behaviour is not influenced by the proximity of other adult budworm. At high population densities, males are apparently able to locate females before or as soon as they start to call, suggesting that communication is short range. Longer distance communication probably operates at low population densities. Population regulation by disrupting mating behaviour is therefore unlikely to succeed except at relatively low population densities.