GEOSTATISTICAL CHARACTERIZATION OF THE SPATIAL-DISTRIBUTION OF ADULT CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE) EMERGENCE

Geostatistical methods were used to characterize spatial variability i n western (Diabrotica virgifera virgifera Leconte) and northern (Diabr otica barberi Smith & Lawrence) corn rootworm adult emergence patterns . Semivariograms were calculated for adult emergence density of corn r ootworm populations in fields of continuous corn and rotated (corn/soy bean) corn. Adult emergence densities were generally greater for north ern corn rootworms than for western corn rootworms. The spatial struct ures of the adult rootworm emergence were aggregated as described by s pherical spatial models for western corn rootworm and exponential mode ls for northern corn rootworm. Range of spatial dependence varied From 180 to 550 m for western corn rootworm and 172 to 281 m for northern corn rootworm. Semivariogram models were used to produce contour densi ty maps of adult populations in the fields, based on grid sampling of actual emerging adult populations.