Incidence of natural control agents of the velvetbean caterpillar and response of its predators to insecticide treatments in Brazilian soybean fields

Abstract

Larvae of the velvetbean caterpillar Anticarsia gemmatalis Hubner were collected from soybean (Glycine max (L.) Merrill) to determine their population levels and percentage of infection by the fungus, Normuraea rileyi (Farlow) Samson. Seasonal population levels of larvae and adults of the carabid predator, Calosoma argentatus granulatum (Perty) were determined by pitfall trap collections. The relationship between resurgence of Anticarsia and populations of Calosoma, geocorids, and nabids as influenced by insecticides was studied. Fungus attack began in February during the pod development stage when the third generation of Anticarsia larvae were reaching a peak and 100% of larvae observed on foliage were infected three weeks later. Activity of Colosoma coincided closely with population levels of the third generation of Anticarsia. Geocorid and nabid populations were severely affected by monocrotophos and methyl parathion treatments whereas diflubenzuron, a chitin inhibitor, had no apparent deleterious effect.