Effects of vegetation textures on the density and herbivory of the soybean stem fly Melanagromyza sojae (Zehntner) in soybean cropping systems
1991
Cayme, T.L.
Four monoculture and four polyculture cropping systems were compared on the basis of plant complexity and arthropod species diversity. Polycultures showed the tendency to support more diversity for natural enemy species and vegetation per habitat space than monoculture. This trend was due to the greater spatial heterogeneity and complexity. There was significantly lower weed biomass in polyculture than in monoculture. Apparently, shading provided by overlapping soybean/sweet corn canopies helped suppress weeds. Populations of adult stem fly, Melamagromyza sojae (Zehntner) (Diptera: Agromyzidae) were greater in soybean monoculture kept weed-free throughout the season than in soybean monocultures and polycultures (intercropped with corn) left weedy for two or four weeks after planting or throughout the season. Significantly, more larvae were also counted in monocultures and polycultures kept weed-free for four weeks after planting on weed-free throughout the season. Stem fly densities and percent infestations were apparently lower in the more weedy monoculture and polyculture cropping systems. Predaceous arthropods were significantly more numerous in polycultures than in monoculture cropping systems. Eurytoma wasps parasitized M. solae larvae more efficiently in the more weedy cropping systems than in weed-free monocultures.
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