Geostatistical investigation of the small-scale spatial variation of western corn rootworm (Coleoptera : Chrysomelidae) adults

Field studies were conducted in 1994 and 1995 to characterize the spatial d istribution of western corn rootworm, Diabrotica virgifera virgifera LeCont e, adults in field corn using whole-plant counts as the sampling tool. Geos tatistical methods were used to determine the small-scale spatial, relation ships of adults within fields during different corn phenology periods and a s beetle population densities changed. Because the focus was on small-scale spatial variation, trend surface regression methods were used to remove la rge-scale variation. Geostatistical analysis of whole-plant count data indi cated that no small-scale spatial correlation was present among samples tak en > 5.3 m apart in 5 of 55 semivariograms that were plotted. The 3 signifi cant small-scale spatial relationships occurred around peak pollination per iods, and during this time, samples were spatially dependent at distances o f <30-40 m apart. Nc small-scale spatial correlation was detected during ot her growth stages. The small-scale spatial patterns detected also appeared to be independent of beetle density within the range of densities (0.1-5.0 beetles per plant) that were sampled. Data suggest that beetle spatial patt erns can be affected by changes in crop phenology. Contrasts in corn phenol ogy within and among fields should be considered when developing sampling p rograms based on visual beetle counts.