Laboratory Tests on Grasshoppers with Thuringiensin, B-Exotoxin of Bacillus Thuringiensis, 1985

Thurin-giensin was tested on third-instar nymphs and adults of 2 economically important grasshopper species. Sunflower seedlings, 15-30 cm tall, planted 6 to a flat, were sprayed to runoff with the appropriate concentration of thuringiensin mixed with water. For controls, water only was sprayed on the plants. Laboratory-reared grasshoppers were held without food 24 h before testing. The tests were conducted in a greenhouse with cages measuring 30 cm on a side. Nymphs and adults were placed in separate cages. Untreated foliage was placed in cages where treated foliage was entirely consumed. Mortality counts were taken daily for 20 days, but only 15-day mortality is reported for nymphs, and 20-day mortality for adults. Chi-square tests were used to compare each treatment with the control.