Assessment of grasshopper abundance in cereal crops using pan traps

Abstract

Grasshoppers and locusts frequently invade cereal crops from adjacent source habitats. The lack of a simple, reliable sampling method for grasshoppers in cereal crops has hindered both the study of grasshopper dispersal into crops and the evaluation of various management alternatives. Water-filled pan traps were tested as a means of assessing grasshopper abundance. In comparisons of species proportions in sweep net and pan trap samples in fallow fields, there was a good correlation between the two methods, but some differences were noted. In particular, proportions of Chorthippus curtipennis tended to be greater in sweep samples than in pan traps. As a demonstration of the potential of pan traps for study of spatiotemporal dynamics of grasshopper and locust invasion of crops, a grid of pan traps was placed within a field of barley. Geostatistical methods were used to produce maps of grasshopper abundance within the barley field on five occasions during the growing season. Overall, pan traps show promise as a means of studying grasshopper dispersal into field crops.