Numerical Analysis of a Jack Pine Budworm 1 Outbreak in Various Densities of Jack Pine

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Abstract
A life table study of the jack pine budworm Choristoneura pinus Freeman was superimposed on a stocking level study of dense jack pine in northern Minnesota to assess the relation of budworm numbers to density of stands. The analysis of population changes revealed that the survival rate of large larvae was most closely associated with survival of the whole generation. However, at low insect density small larva survival was more important. Stand density and associated male cone production accounted for a large part of the variation in budworm dispersal and survival rate of small larvae. During the declining phase of the infestation indirect evidence suggests there were changes in population quality associated with reduced male cone production. Above normal humidities and subnormal temperatures occurred during the larval stage the 3rd year when the infestation collapsed. Defoliation intensity was higher in the dense stands. Precommercial thinning from below in dense jack pine stands will maximize larval dispersal loss and minimize male cone production and defoliation.