Spruce Budworm (Lepidoptera:. Tortricidae) Larval Populations and Field Persistence of Bacillus thurigiensis after Treatment in Wisconsin1

Abstract

In 1981, 1 year posttreatment, densities of Choristoneura fumiferana (Clemens) larvae and levels of defoliation were lower on balsam fir, Abies balsamea(L.) Mill., in plots treated with Thuricide 16B or Dipel 4L, formulations of Bacillus thuringiensis Berliner var. kurstaki, than in check plots. Viable endospores were recovered from balsam fir foliage in four treated plots, although total field persistence, i.e., duration of pathogenicity, of B. thuringiensis was negative.