Geostatistical investigation of the small-scale spatial variation of western corn rootworm (Coleoptera: Chrysomelidae) adults
1999
Darnell, S.J. | Meinke, L.J. | Young, L.J. | Gotway, C.A.
Field studies were conducted in 1994 and 1995 to characterize the spatial distribution of western corn rootworm, Diabrotica virgifera virgifera LeConte, adults in field corn using whole plant counts as the sampling tool. Geostatistical methods were used to determine the small-scale spatial relationships of adults within fields during different corn phenology periods and as beetle population densities change. Because the focus was on small-scale spatial variation, trend surface regression methods were used to remove large-scale variation. Geostatistical analysis of whole-plant count data indicated that no small-scale spatial correlation was present among samples taken >5.3 m apart in 5 of 55 semivariograms that were plotted. The 3 significant small-scale spatial relationships occurred around peak pollination periods, and during this time, samples were spatially dependent at distances of <30-40 m apart. No small-scale spatial correlation was detected during other 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 patterns can be affected by changes in crop phenology. Contrasts in corn phenology within and among fields should be considered when developing sampling programs based on visual beetle counts.
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