Effects of soil-dwelling predators and organic treatments on the cabbage root fly Delia radicum (Diptera: Anthomyiidae) in greenhouse radish

摘要

Delia rod/aim is the most damaging pest species for radish in Dutch greenhouses. Application of broad-working soil pesticides will be forbidden in near future, which strengthens the necessity to find alternative control methods. The objective of thisstudy was to test the effect of soil-dwelling predators on D. radicum and to encourage establishment of these predators in greenhouses. The commercially available predators Hypoaspis miles (Acari: Laelapidae) and Aleocbara bilineata (Coleoptera: Staphilinidae) were tested as potential biocontrol agents for D. radicum. The predatory mites H. miles reduced damage by D. radicum by 58%, whereas releases of adult beetles of A. bilineata above ground had no significant effect. Burying pupae of Delia antiqua parasitized by A. bilineata however, reduced damage by D. radicum by 52%. Adding organic matter to soil did not Significantly increase survival of H. mites. Fresh yard waste compost and white peat stimulated ovipostion of D. radicum, whereas cocopeat didnot.