Crop pollination management needs flower-visitor monitoring and target values

Abstract

Despite the crucial importance of biotic pollination for many crops, land managers rarely monitor the levels of crop pollination needed to guide farming decisions. The few existing pollination recommendations focus on a particular number of honeybee or bumblebee hives per crop area, but these guidelines do not accurately predict the actual pollination services that crops receive. We argue that pollination management for pollinator-dependent crops should be based on direct measures of pollinator activity. We describe a protocol to quickly perform such a task by monitoring flower visitation rates. We provide target values of visitation rates for crop yield maximization for several important crops by considering the number of visits per flower needed to ensure full ovule fertilization. If visitation rates are well below or above these target values, corrective measures should be taken. Detailed additional data on visitation rates for different species, morpho-species, or groups of species and/or flower-visitor richness can improve pollination estimates. Synthesis and applications. We present target values of visitation rates for some globally important pollinator-dependent crops and provide guidance on why monitoring the number and diversity of pollinators is important, and how this information can be used for decision-making. The implementation of flower monitoring programmes will improve management in many aspects, including enhanced quality and quantity of crop yield and a more limited spillover of managed (often exotic) pollinators from crop areas into native habitats, reducing their many potential negative impacts.