Evaluation of the effectiveness of Bacillus thuringiensis var. entomocidus as a pest control agent to replace chemical pesticides in alfalfa fields in Israel

The Egyptian cotton leafworm, Spodoptera littoralis Boisd., is the main important pest of alfalfa in Israel. Population levels of other pests usually do not reach the economic threshold. Nine chemical insecticide applications (7 spray applications and 2 granular fluorosilicate baits) were required to control S. littoralis during the season of 1984 (in which infestation level was high) whereas only 5 applications of a Bacillus thuringiensis var. entomocidus (Bte) preparation (3 sprays and 2 baits) produced the same effect. During 1983 and 1985 pest populations were moderate and only 6 chemical pesticide applications were required. A bait of Bte on wheat bran, Coax^®, developed in the present study was effective in the control of large larvae (instars 4-6). Hay yields of fields treated with Bte were similar to the yields of a conventionally treated field. The best control of large larvae was obtained by applying the bait preparation under the wind row during the alfalfa cutting.