Populations of Anticarsia gemmatalis were evaluated on soyabeans in Rio Grande do Sul, Brazil, during 1982-90. Larvae were most numerous between 30 January and I March when soyabean plants were between full flowering (R2) and pod filling (R5). Mortality due to parasitoids and pathogens varied from 10 to 89%, with an average of 56%. Of this 29% was due to Nomuraea rileyi, 15% to Microcharops bintaculwa and 6% to Entomophthora sphaerosperma. In 4 of the 8 cropping seasons, there was no significant difference in grain yields for the areas with natural biological and chemical control. none