Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2007
Publication Date: 3/4/2008
Citation: Herrick, N.J., Reitz, S.R., Carpenter, J.E., O'Brien, C.W. 2008. Predation by Podisus maculiventris (Heteroptera: Pentatomidae) on Plutella xylostella (Lepidoptera: Plutellidae) larvae parasitized by Cotesia plutellae (Hymenoptera: Braconidae) and its impact on cabbage. Biological Control. 45:386-395. Interpretive Summary: Insect predators and parasitoids interact in a variety of ways that can impact control of agricultural pests. Sometimes interactions between predators and parasitoids result in greater than expected populations of a pest. Understanding the combined effect of predators and parasitoids is important for optimizing the use of insects to control pests in agricultural. Research conducted by USDA, ARS scientists at the Center for Medical, Agricultural and Veterinary Entomology has shown that the predator, spined soldier bug, prefer to feed on diamondback moth caterpillars three days after they have been parasitized by the parasitic wasp, Cotesia plutellae. Further evaluations in a simulated cabbage setting revealed that the predator, and the parasitic wasp, Cotesia plutellae, interact negatively and produce greater than expected diamondback moth populations and damage to cabbage plants. This information can help guide future biological control efforts.
Technical Abstract: The diamondback moth, Plutella xylostella (L.), is the primary pest of plants in the family Brassicaceae. Biological control offers an alternative to insecticides, but little is known of whether multiple natural enemies have additive, antagonistic, or synergistic effects on P. xylostella populations. No-choice and choice tests were conducted in the laboratory at 24 h and 72 h post-development to determine if Podisus maculiventris (Say) has a preference for P. xylostella larvae parasitized by Cotesia plutellae (Kurdj.) or unparasitized larvae. In no-choice tests, P. maculiventris consumed greater numbers of parasitized larvae and the number of larvae consumed decreased with increasing age of the larvae. In both tests at 24 h, P. maculiventris showed no preference for parasitized or unparasitized larvae. In both tests at 72 h, P. maculiventris preferentially preyed on parasitized larvae. Field studies were conducted in 2002 and 2003 to test if P. maculiventris and C. plutellae have an additive, antagonistic or synergistic effect on P. xylostella in cabbage (Brassica oleracea var. capitata (L.) ‘Bonnie’s Hybrid’ and ‘Constanza’) by comparing P. xylostella populations and plant damage in replicated field cages containing 1) P. xylostella, 2) P. xylostella with P. maculiventris, 3) P. xylostella with C. plutellae and 4) P. xylostella with P. maculiventris and C. plutellae. Over the entire 2002 season no treatments differed from populations in the P. xylostella only control. However, C. plutellae alone reduced P.xylostella populations and overall plant damage late in the season. Over the entire 2003 season C. plutellae alone significantly reduced P. xylostella populations but not plant damage. Cotesia plutellae reduced P. xylostella populations late in the 2003 season. In all cases the combined natural enemy treatment did not significantly reduce plant damage when compared with the P. xylostella only control. Podisus maculiventris and C. plutellae together act antagonistically on P. xylostella populations and plant damage.