Predation on eggs and larvae ofHeliothis virescens [Lep.: Noctuidae] by an adult predator complex in cage studies on cotton

Abstract

Predation by a predator complex consisting of adults of the lygaeidGeocoris punctipes (Say), the nabidsNabis roseipennis Reuter and/orTropiconabis capsiformis Germar and the coccinelids,Hippodamia convergens Guerin-Meneville andColeomegilla maculata (DeGeer) onHeliothis virescens (F.) eggs, 1st-instar larvae or both on late pinhead square and early bloom stage cotton was evaluated in field cages in Mississippi. Prey densities of 4 (11, 512/ha) or 8 per cage and predator: prey (P:p) ratios of 1∶1, 2∶1, 3∶1, 4∶1 and 5∶1 were used. Prey were labeled with phosphorus-32 or carbon-14 to determine predator ingestion and effectiveness. Average percent egg predation as a function of P:p ratio ranged from 2.1 to 12.1 for a 48 h period. The average percent predation on larvae as a function of P:p ratio ranged from 5.3 to 22.0. The hemiptera fed more than the coleoptera on larvae, andG. punctipes was the best egg predator. For the range of predator densities used, the average area of discovery for the predator complex was 6.98 × 10−3 m/day and 2.34 × 10−2 m/day when exposed to eggs and larvae, respectively.