Relative importance of predators and parasitoids for cereal aphid control

• Published in: Proceedings of the Royal Society. B, Biological sciences Vol. 270; no. 1527; pp. 1905 - 1909
• Main Authors: Schmidt, Martin H., Lauer, Andreas, Purtauf, Tobias, Thies, Carsten, Schaefer, Matthias, Tscharntke, Teja
• Format: Journal Article
• Language: English
• Published: England The Royal Society 22.09.2003
• Subjects: Agroecosystems; Animals; Aphidiidae; Aphids - parasitology; Aphids - physiology; Araneae; Biological Control; Ecology; Edible Grain - physiology; Food Chain; Hyperparasites; Natural enemies; Parasitism; Parasitoids; Population Density; Population Dynamics; Predation; Predators; Sitobion Avenae; Spiders; Wasps - physiology; Wheat; Winter Wheat
• ISSN: 0962-8452; 1471-2954
• DOI: 10.1098/rspb.2003.2469

Field experiments with manipulations of natural enemies of plant-feeding insects may show how a diverse enemy group ensures an important ecosystem function such as naturally occurring biological pest control. We studied cereal aphid populations in winter wheat under experimentally reduced densities of: (i) ground-dwelling generalist predators (mostly spiders, carabid and staphylinid beetles); (ii) flying predators (coccinellid beetles, syrphid flies, gall midges, etc.) and parasitoids (aphidiid wasps), and a combination of (i) and (ii), compared with open controls. Aphid populations were 18% higher at reduced densities of ground-dwelling predators, 70% higher when flying predators and parasitoids were removed, and 172% higher on the removal of both enemy groups. Parasitoid wasps probably had the strongest effect, as flying predators occurred only in negligible densities. The great importance of parasitism is a new finding for aphid control in cereal fields. In conclusion, a more detailed knowledge of the mechanisms of natural pest control would help to develop environmentally sound crop management with reduced pesticide applications.