Pollinator visitation decline due to pesticide application beyond threshold frequency brings down crop yield

Abstract

The deleterious effects of pesticides on pollinating insect abundance are well established but the relationship among pesticide application, pollinator decline and the corresponding change in marketable yield is not fully understood. In this study, we assessed what level of pesticide exposure causes maximum pollinator loss and at that level of pollinator loss if there is any crop yield loss. We primarily assessed pollinator crop flower visitation in 27 aubergine farms with different degrees of pesticide application. Subsequently, we also observed pollinator activity and aubergine yield (fruit set) in a semi-controlled field experiment with four different pesticide treatments. Pesticide application frequency was the most important driver of pollinator visitation compared with quantity. Pesticide spray above once a week caused a drastic drop in pollinator visitation in a non-linear fashion showing a threshold of pesticide application. In high pesticide frequency experimental plots, pollinator visitation was significantly lower than in control, low and medium frequency plots. This resulted in lowering of aubergine fruit set by 27.4% in high pesticide frequency plots. Use of synthetic pesticides to safeguard yield seems to be doing just the opposite by bringing down yield from pesticide-induced pollinator limitation.