PARASITISM AND PREDATION AS AGENTS OF MORTALITY OF WINTER MOTH POPULATIONS IN NEGLECTED APPLE ORCHARDS IN NOVA-SCOTIA

1. This study compared the roles of pupal mortality and parasitism in winter moth (Operophtera brumata) population dynamics in Nova Scotian apple orchards and assessed the importance of beetles as pupal predato rs. 2. The component of pupal mortality termed predation accounted for greater stage-specific mortality of winter moth than parasitism by Cy zenis albicans in four neglected orchards. 3. Parasitism by Cyzenis al bicans was not spatially density-dependent in any orchard, whereas the predation component of pupal mortality was spatially density-dependen t in the two orchards most densely populated by winter moth. 4. Field experiments indicated that over 60% of pupal predation may be attribut ed to beetles, and that about 46% of pupal predation occurred within 4 weeks after pupal drop. 5. Mortality of introduced populations of win ter moth in Nova Scotia resembles that of native populations in Englan d where density-dependent predation regulates the winter moth populati on and reduces the parasitoid population to minimal levels. The situat ion in Nova Scotia appears to have changed appreciably since the estab lishment of parasitoids into the system in the 1950s.