Seasonal prevalence of two parasitoids attacking Russian wheat aphid, Diuraphis noxia, was compared between areas of high and low crop diversity in northwestern Great Plains. The parasitoids Aphelinus albipodus and Lysiphlebus testaceipes were sampled periodically for two years using D. noxia-infested plant materials. Samples were taken from farm sites scattered in contiguous wheat production areas of northcentral Colorado, western Nebraska, and southeastern Wyoming. Winter wheat production was often diversified with spring-sown crops in the region. We hypothesized that parasitism of D. noxia may occur more frequently in diversified wheat production systems and agricultural landscapes than in simple wheat production areas and landscapes. Each farm site consisted of a crop production area and adjacent grassland. Cropping of within farm sites was either diverse (wheat-sunflower-fallow rotation) or simple (wheat-fallow rotation). Landscape surrounding farm sites was either heterogeneous or homogeneous based on landscape metric characteristics. Early in the season (late April to early June) when spring-sown plants were not emerged or young, parasitism by Aphelinus albipodus was often more frequently detected in the simple wheat production system and homogeneous landscape. Late in the season (August to early October) when spring-sown plants were mature, parasitism by A. albipodus and L. testaceipes were often detected more frequently in diverse wheat production system and heterogeneous landscape. The effect of crop and landscape diversity on frequency of parasitism by D. noxia parasitoids changed with crop plant phenology.
Species 1: Homoptera Aphididae Diuraphis noxia (Russian wheat aphid)
Species 2: Hymenoptera Aphelinidae Aphelinus albipodus
Species 3: Hymenoptera Aphidiidae Lysiphlebus testaceipes
Keywords: conservation biological control
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