Movement of Corn Rootworm Larvae (Coleoptera: Chrysomelidae) Between Border Rows of Soybean and Corn in a Strip Intercropping System

Strip intercropping of corn may provide spatial and temporal diversity for management of extended-diapause corn rootworm populations. Strip-intercropped corn may sustain infestations of corn rootworm larvae attributable to migration of larvae into 1st-yr corn from soil previously planted to corn. Row-specific distribution of corn rootworm eggs and adult emergence were determined in a strip intercropped system, and effects of interstrip cultural and insecticidal treatments on rootworm infestation of outer rows were evaluated. Corn rootworm eggs were found in all rows of strips previously planted to corn. Root injury ratings were significantly higher in the outer rows than in the interior rows of corn adjacent to the previous year’s corn strips. Oilseed meal and insecticide treatments were associated with lower corn rootworm adult emergence and larval root injury than was found in untreated plots. Higher rootworm adult emergence and root injury scores in tillage treatments, where the soil was disturbed by ripping with a cultivator shank, were attributed to increased soil pore space that facilitated larval movement into adjacent corn strips. Fewer adults emerged and less root injury occurred in outer rows of corn adjacent to soybean strips that were subjected to interrow soil compaction from wheel traffic. In severely infested fields, deliberate compaction of interrow soil or incorporation of cruciferous plant material into soil between strips are possible noninsecticidal management options for reducing severe corn rootworm infestation of outside rows of corn in strip intercropping systems.