D3191: Impact of pesticide application on wild bee abundance and diversity in a semi-arid Cucurbita agroecosystem

Wild bees provide an invaluable ecosystem service in the form of pollination, particularly in agricultural systems. However, the pesticides sprayed on croplands to control unwanted pests can have the unintended consequence of harming local bee populations. In this study, we aimed to determine the effect of pesticide application on the diversity and abundance of wild bees in a Cucurbita agroecosystem. We predicted that in the days following pesticide application, there would be a reduction in wild bee abundance and diversity and that field sites that received a greater number of pesticide treatments would have reduced wild bee abundance and diversity. We deployed 8-10 pantraps at each of our 20 field sites biweekly for a total of 503 pantraps in Cucurbita production fields in the semi-arid Southern High Plains Region of Texas to characterize the bee community. Local partners provided pesticide application dates and detailed agronomic practice data. Captured bees were identified to the species level. Each field site received on average 2.4 aerial pesticide treatments across the sampling period. We identified a total of 59 unique bee species (23 genera, 5 families) across all sampling periods and all locations. Surprisingly, there was still considerable wild bee diversity despite intensive land management. While species richness in our Cucurbita agroecosystem was lower, total family richness rivaled levels previously observed in nearby natural ecosystems, indicating that bees with variable life histories are able to persist despite frequent pesticide exposure.