Dan A. Wolfenbarger

Tobacco Budworm: Structure-Activity of Aziridine Chemosterilants as Fumigants

Numbers AI3-52457, -50042, -50765, and -61587 were the most effective of 25 aziridine chemosterilants evaluated as fumigants against the tobacco budworm Heliothis virescens (F.). AI3-50042 did not cause complete sterility of males, and these males were equal to untreated males in terms of sperm transfer.

Relationships between laboratory bioassay-derived potencies and field efficacies of Bacillus thuringiensis isolates with different spectral activities☆☆☆

Abstract Bacillus thuringiensis isolates with different spectral activities were not equally efficacious when applied to cabbage at the same number of IUs/ha for protection against larvae of the cabbage looper, Trichoplusia ni. Preparations of the isolates were standardized against T. ni larvae. Variety galleriae isolates (HD-196 and HD-153) were the most efficacious per applied IU, and a K-73 type variety kurstaki (HD-73) was the least efficacious per applied IU. A variety thuringiensis (HD-264) and a K-1 type variety kurstaki (HD-1) were intermediate in efficacy per applied IU. Speed of kill and, to some extent, differences in the amount of food consumed appear to be responsible for the differences in efficacy per applied IU. When more potent B. thuringiensis isolates are discovered and developed, the recommended field dosages for the new isolates must be determined by actual field experimentation rather than by extrapolation from existing HD-1 data.