The half-life of spores and endocrystals ofBacillus thuringiensisBerliner on soybean leaves was less than 24 h, since 65% of the insecticidal activity, and 90% of the spore viability, was lost during the 1st day. However, some insecticidal activity could be detected at 7 days postapplication. The half-life of the nucleopolyhedrosis virus ofHeliothis(Baculovirus heliothis) was>2<3 days. Viral activity could not be detected after 14 days' exposure on soybean leaves.