C.M. Riley, T. Smith


Executive Summary

The use of tannic acid as a spray mix additive to enhance the biological effectiveness of B.t. was investigated in a series of laboratory bioassays.

Several spray mixes containing B.t and tannic acid at various concentrations were applied to new balsam fir foliage which was then used in a feeding bioassay with fourth instar spruce budworm larvae. Larval mortality and development were monitored for up to 13 days post-treatment.

The addition of tannic acid did not enhance B.t toxicity; moreover in most cases tannic acid appeared to reduce B.t toxicity toward fourth instar spruce budworm larvae.