Comparative Efficacy of Four Insect Predators of the Bollworm and Tobacco Budworm 1 , 2

Abstract

The comparative efficacy of 4 predators against 3 different stages of the cotton bollworm, Heliothis zea (Boddie), or the tobacco budworm, Heliothis virescens (F.), was studied in the laboratory. The species studied were Chrysopa carnea Stephens, Geocoris punctipes (Say), Coleomegilla maculata (DeGeer), and Podisus maculiventris (Say). Two of these predators were also evaluated for control of the tobacco budworm on cotton in field cages. Under limited searching requirements, C. maculata was generally the most efficient predator of Heliothis eggs and 1st stage larvae. However, when the 1st stage predators were compared, C. carnea was the most efficient predator on 1st instars. Third stage nymphs and adults of P. maculiventris were the most efficient predators of the 3rdstage larvae. Under expanded searching requirements, C. carnea larvae were the most efficient of the immature stages of predators on Heliothis eggs and 1st instars. As adults, C. maculata were the most efficient predators on eggs while G. punctipes were the most effective predators on 1st stage larvae. Third instars and adults of P. maculiventris consumed more 3rd instars of Heliothis than the other predators studied. Releases of C. carnea and P. maculiventris at rates of 100,000/acre in field cages resulted in substantial reductions in the number of tobacco budworm larvae. The reductions effected by C. carnea were more evident in the egg and small larva numbers while the reductions attributed to P. maculiventris occurred mainly when the tobacco budworm larvae were larger.