Laboratory and Field Evaluations of Pathogen-Adjuvant Treatments1

Abstract

Mortality among 24-h-old Trichoplusia ni (Hübner) or Heliothis zea (Boddie) larvae in bioassays of formulations containing either Bacillus thuringiensis Berliner or a nuclear polyhedrosis virus. Baculovirus heliothis. was significantly lower when cotton foliage was the test substrate than when soybean or cabbage was used. The incorporation of a soybean flour adjuvant (with one exception) significantly increased mortality among test larvae when compared with standard water-B. thuringiensis or water-virus suspensions. Increasing the application rate of the soybean flour adjuvant from 1.12 to 4.49 kg/ha did not significantly increase larval mortality. Spray nozzle size (TX-2, TX-4, TX-8, TX-12) did not affect mortality among test larvae exposed to soybean foliage treated with formulations containing the soybean flour adjuvant; however, average mortality for the formulation containing the adjuvant was eight times higher than that for the standard water-virus suspension containing the same amount of virus. Based on the half-life of each suspension, aqueous cottonseed and soybean adjuvants plus virus suspensions were ca. 3.3 and 2.2 times more effective, respectively, under field conditions, than a virus-water suspension.