Spatial modeling of preferred wireworm (Coleoptera: Elateridae) habitat

Potential damage to crops after the Conservation Reserve Program is widespread. One probable result is the increased occurrence of soil-insect pests, primarily wireworms (Coleoptera: Elateridae). The likelihood of wireworm problems in the Iowa Conservation Reserve Program was compounded by the large amount of land enrolled in the program and the economic importance of corn, Zea mays L., the crop most often damaged by wireworms in the state. As a result, farmers need to consider pest management options that should include pest scouting. Wireworm presence/absence data from 1995 and 1996, and estimates of soil moisture from 89 Conservation Reserve Program fields were used to estimate variables useful for identifying where wireworms are more likely to occur. The most useful variables were a soil-moisture threshold of 17% and a moisture analysis that included meteorological data from only 1 yr before sampling occurred. These variables were coupled with a hydrologic model and embedded in a geographic information systems (GIS) framework. This computerized habitat model was run on the study area, Story County, Iowa, and generated a map indicating areas where wireworms were more likely to occur and where scouting should begin. Results of the model run indicate that most of Story County is suitable wireworm habitat and that there were areas considered highly favorable. The map generated by this computer model can be used as a guide for directing scouting within a field but does not identify areas where management tactics are necessary. The methodology used in this study is relatively simple, yet it performs the difficult task of combining time, space, and climatological variables to evaluate wireworm habitat over a landscape. Moreover, it demonstrates one application of GIS technology in a discipline where the subject has characteristics that are inherently spatial.