Dispersal of the Japanese Beetle (Coleoptera: Scarabaeidae) in Strip-Cropped Soybean Agroecosystems

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Abstract
Marked Japanese beetles, Popillia japonica Newman, were released and recaptured in experimental plots to test the effect of contrasting types of strip-cropped soybean agroecosystems on beetle dispersal. Experimental treatments were soybean monoculture, soybean strip-cropped with dwarf sorghum (≍1 m tall), and soybean strip-cropped with tall sorghum (>2 m tall). Three hundred marked Japanese beetles were released in the center soybean strip of each treatment in small (0.11 ha) and large (0.45 ha) experimental plots. Beetles remained longer in the center soybean strip in the strip-cropped bicultures than in the monocultures indicating that the sorghum strips inhibited their movement. Dispersal rates were similar in dwarf and tall sorghum treatments despite differences in plant height. Significantly more marked beetles in the small plots, however, emigrated from the ends of the center soybean strip in the tall sorghum biculture than in the other two treatments indicating that tall sorghum oriented beetles to move parallel to intercropped strips. Japanese beetles responded to the sharp boundaries between host and nonhost habitat patches, as has been previously reported for host specific herbivorous insects. Results suggest that strip-cropping can affect the movement of polyphagous herbivorous insects and provide benefits for pest management in large-scale agroecosystems.