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.

Keywords:

• population sampling
• geostatistics
• Orthoptera
• Acrididae
• crop protection

Acknowledgements

L. DeFoliart, R. Carrillo, R. Torgerson, S. Gneiting, and W. Conner assisted with data collection. The manuscript was improved by the suggestions of A. Hagerty and A. Pantoja.