Predation on Immature Parasitoids and Its Impact on Aphid Suppression

• Published in: Oecologia Vol. 126; no. 2; pp. 292 - 304
• Main Authors: COLFER, R. G, ROSENHEIM, J. A
• Format: Journal Article
• Language: English
• Published: Berlin Springer-Verlag 01.01.2001; Springer
• Subjects: Aphididae; Beetles; Biological and medical sciences; Biological control; Coccinellidae; Community Ecology; Control; Fundamental and applied biological sciences. Psychology; Gossypium hirsutum; Herbivores; Mummies; Natural enemies; Parasite hosts; Parasitism; Parasitoids; Phytopathology. Animal pests. Plant and forest protection; Population growth; Population growth rate; Predators; Protozoa. Invertebrates; Malvaceae; Aphis gossypii; Coleoptera; Insecta; Biological control; Aphidiidae; Fiber crop; Pest; Homoptera; Entomophagous; Beneficial animal; Dicotyledones; Angiospermae; Aphididae; Density dependence; Aphidoidea; Coccinellidae; Parasitoid; Larva; Hippodamia convergens; Arthropoda; Trophic cascade; Spermatophyta; Gossypium hirsutum; Predation; Hymenoptera; Invertebrata; Herbivore natural enemies; Density-dependent predation; Intraguild predation
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s004420000510

Many predatory arthropods eat both unparasitized herbivores and herbivores that are parasitized and contain the immature stages of endoparasitoids, a form of intraguild predation. Thus, the biological control of herbivorous arthropods can be either enhanced or disrupted by introducing a predator species to an existing host-parasitoid system. We evaluate the impact of introducing a predator, the convergent ladybird beetle, Hippodamia convergens, on the biological control of the cotton aphid, Aphis gossypii, by the parasitoid Lysiphlebus testaceipes, under field conditions. Predation on immature parasitoids by H. convergens was intense: 98-100% of aphid mummies were consumed by the end of the experiment, and H. convergens substantially reduced immature parasitoid populations. Despite the negative impact of H. convergens on aphid parasitoids, aphid population suppression was greatest in treatments containing both H. convergens and parasitoids. The parasitoid alone or in combination with H. convergens suppressed cotton aphids in a density-dependent manner and increased total plant leaf area and biomass, H. convergens did not substantially alter the percentage of aphids mummified by parasitoids and showed a partial feeding preference for unparasitized aphids over aphid mummies. We conclude that under conditions where a predator shows both a partial preference for unparasitized hosts and high levels of predation on unparasitized hosts, we may expect the predator to improve suppression of herbivores even if it produces high levels of intraguild predation. While intraguild predation is an important ecological interaction in the early-season cotton agroecosystem, it does not disrupt cotton aphid biological control.