Mortality of the white pine weevil associated with silvicultural practices in jack pine plantations

Abstract

A synthesis of white pine weevil (Pissodes strobi Peck) mortality caused by predation (insects, birds, and mammalian predators), crowding of pupae, and abiotic factors, acting under different stand conditions given by the type of reforestation, depth of the duff, distance from woody debris, and presence of competing vegetation is presented, based on a four-year study conducted in northeastern Ontario. The type of reforestation (planted vs. aerial seeding) did not influence mortality to immature weevils in the leaders from either bird predation, insect predators and parasitoids or crowding of pupae, but 16% more weevils died during winter in a planted than in a seeded stand suggesting that there was an effect of site condition or small mammal predation on overwintering adults in the duff. Over all conditions, overwintering mortality averaged 76-92% with small mammal predation representing about 5-13%. Site conditions which augmented small mammal populations and predation, such as proximity to woody debris and presence of competing vegetation, had no effect on overwintering mortality of the weevils. The most important factor influencing overwintering mortality was likely the depth of duff where an inverse relationship was observed between mortality and depth. Forest managers should address conditions of duff depth and small mammal predation to increase the already significant overwintering mortality of adult weevils in young jack pine stands. Key words: Pissodes strobi, silvicultural treatments, planted and seeded stands, competing vegetation, duff layers, small mammal predation, overwintering mortality