RELATIVE POTENCIES OF 50 ISOLATES OF BACILLUS THURINGIENSIS FOR LARVAE OF THE SPRUCE BUDWORM, CHORISTONEURA FUMIFERANA (LEPIDOPTERA: TORTRICIDAE)

Abstract

Can. Ent. 115: 815-822 (1983) Fifty Bacillus thuringiensis (B.t.) isolates representing K-1, galleriae, K-73, thuringiensis, aizawai, dendrolimus, tolworthi, kenyae, darmstadiensis, alesti, and entomocidus crystal antigen types were bioassayed against fifth-instar spruce budworm, Choristoneura fumiferana (Clem.), larvae. In addition, larvae reared on diet with and without aureomycin were tested for their susceptibility to B.t. The data indicated no significant differences in susceptibility to B.t. among insects reared on aureomycin or on aureomycin-free diet, but differences were evident in larval growth and mortality among untreated controls. None of the 50 isolates bioassayed was any more toxic to the budworm than is the strain used at present in commercial preparations of B. thuringiensis. ResumeCinquante isolats de Bacillus thuringiensis (B.t.) reprksentant les types antigkniques i l'ktat cristallisk K-1, galleriae, K-73, thuringiensis, aizawai, dendrolimus, tolworthi, kenyae, darmstadiensis, alesti et entomocidus ont CtC testks contre des larves au cinquibme stade de la tordeuse des bourgeons de l'kpinette, Choristoneura fumiferana (Clem.). De plus, la vulnkrabilitk envers B.t. des larves klevkes avec une alimentation additionnke ou exempte d'aurkomycine a kt6 exarninke. Les rksultats n'indiquent aucune diffkrence quant B la vulnkrabilitk des larves alimentkes avec ou sans aurkomycine, mais des diffkrences sont apparues au niveau de la croissance et de la mortalitk chez les lames tkmoins non traitkes. Aucun des 50 isolats testks n'ktait plus toxique pour la tordeuse que la variktk prksentement employke dans des prkparations cornrnerciales.

Development and Current Status of Bacillus thuringiensis for Control of Defoliating Forest Insects

“…Of the naturally occurring strains, the HD-1 isolate of current formulations is one of literally thousands of possible candidates (Martin and Travers 1989), but efforts to identify more potent strains have yielded little benefit for forest insect control to date (Morris and Moore 1983;Dubois 1985;Dubois et al 1989). However, new strains are continually being isolated (Travers et al 1987) and the search for more effective ones is actively pursued.…”

Proceedings, Symposium: Microbial control of spruce budworms and gypsy moths

“…Second y e a r b e n e f i t s could be explained, however, by t h e frequent o b s e r v a t i o n t h a t s u r v i v o r s of B.t. t r e a tments o f t e n produce undersized, and presumeably unhealthy, pupae and moths (Morris and Moore 1983, Smirnoff 1983, Dimond and Spies 1980. I t has been suggested t h a t t h e generation of i n s e c t s descending from t h e s e s t u n t e d s u r v i v o r s may have a low s u r v i v a l p o t e n t i a l (Morris and Moore 1983, Smirnof f e t a 1 .…”

“…Two of these strains were field tested against a gypsy moth infestation and the results were encouraging (Andreadis et al 1982). Morris and Moore (1983) evaluated 50 strains against spruce budworm larvae. Their selection for evaluation was based on the spectrum of activity of the selected strains against the Douglas fir Tussock Moth; none were more potent than the presently comnmercially used HD-1 strain.…”