White pine regeneration in Michigan: Evaluation of white pine weevil and white pine blister rust effects.

摘要

Eastern white pine (Pinus strobus L), once a major component of Michigan forests, was mostly removed by statewide logging and subsequent wildfires in the 1800's. Re-establishment of white pine by planting have been hindered by a native insect, the white pine weevil (Coleoptera: Curculionidae, Pissodes strobi Peck) and an exotic disease, white pine blister rust (Cronartium ribocola Fischer). Identifying silvicultural practices that effectively control white pine weevil and limit white pine blister rust occurrence is important for future regeneration efforts. Differences in weevil incidence, white pine blister rust occurrence, and tree growth were evaluated by in northern Michigan. Thirty-eight percent of all the white pine trees surveyed for this study had no apparent defects. About 40% of trees in natural stands were free of defects compared with 20% of trees in planted stands. White pine blister rust occurred on only 0.07% of trees examined. A study of weevil survival rates and parasitism rates found significantly higher numbers of weevils and parasitized larvae in open grown white pine trees. White pine seedlings were established in areas of Upper and Lower Michigan to collect long-term data on pest incidence and tree growth in stands of different densities and species composition.