THE EFFECTS OF BACILLUS THURINGIENSIS ON PARASITOIDS OF THE WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALS (LEPIDOPTERA: TORTRICIDAE), AND THE SPRUCE CONEWORM, DIORYCTRIA RENICULELLOIDES (LEPIDOPTERA: PYRALIDAE), IN MONTANA

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Abstract
Parasitoid studies were conducted concurrently with a pilot control project to test the efficacy of Dipel® WP, a formulation of Bacillus thuringiensis Berliner, in reducing western spruce budworm, Choristoneura occidentalis Freeman, populations. Twenty-one species of parasitoids were recovered in rearings of the budworm and an associated defoliator, the spruce coneworm, Dioryctria reniculelloides Mutuura and Munroe. Parasitoid population alterations occurred following application. Parasitism by Apanteles fumiferanae Vier. and Glypta fumiferanae (Vier.), which attack prediapausing first-instar budworm, was significantly higher in treatment blocks following B.t. application. Parasitism by Phaeogenes hariolus (Cr.), Cermoasia auricaudata Tns., and Madremyia saundersii (Will), parasitoids of late instars and pupae, was significantly lower following treatment. Comparisons of parasitoid populations were made between pre- and post-spray sampling periods and between treatment and check blocks.