Implications of Spatial Distribution of Insect Populations in Storage Ecosystems

Abstract

Integrated management of storage pests requires understanding storage ecosystems and accurately monitoring pest population levels. Geostatistical techniques for spatial analysis provide a powerful tool to assist in biological interpretation of sample counts and trip captures of insects, as well its interpretations of physical measurements such as grain temperature and moisture content. Contour analysis is 3-step process. Data are first posted to a map of sample points; then a denser grid of data points is generated by interpolation (using one of several algorithms) and contours (lines joining points with equal values) are drawn at some fixed interval. This provides a contour display, showing the value of the variable at all points on the surface represented by the sample points. The utility of this method in stored-product protection is illustrated by a series of studies based on data sets for stored corn. These include comparison of spatial distribution of species and species interactions; analysis of temporal changes in distribution, precision targeting, and evaluation of control measures; interpretation of trap cattch; examination of physical variables and interactions of insects with the physical environment; and analysis of goodness of fit of contour surfaces to the data. The utility of techniques such as grid subtraction and construction of probability contours is demonstrated.