Closing the pollination gap in cacao agroforests: balancing pesticide use and shade management
摘要
Pollination is a key ecosystem service for cacao (Theobroma cacao L.) production, yet natural pollination rates are critically low, partly due to agricultural intensification and the widespread use of agrochemicals. We investigated how conventional crop management practices—specifically the application of an insecticide (cypermethrin), a fungicide (copper oxychloride), and a pollinator breeding substrate (oil palm fibre) affect pollination dynamics in cacao agroforests in Arauca, Colombia. We assessed their individual and combined effects on natural and hand pollination success, alongside environmental factors such as shade, ground cover, and precipitation. We also quantified the pollination gap, defined as the difference between natural and hand pollination, to evaluate pollination efficiency. Using a factorial design and generalized linear mixed models, we found that natural pollination was significantly reduced by pesticide applications, particularly when insecticides and fungicides were combined. In contrast, hand pollination remained largely unaffected by environmental variables. Surprisingly, insecticide application (alone or combined with fungicide) increased hand pollination success, possibly due to reduced flower damage (florivory). As a result, pesticide treatments substantially widened the pollination gap, ranging from nearly eightfold to more than tenfold compared to the control. Notably, increasing shade cover consistently improved natural pollination and narrowed the pollination gap; under high-shade conditions, natural pollination occasionally even outperformed hand pollination. These findings underscore the need for a shift from input-intensive approaches toward integrated management strategies that reconcile productivity with ecological sustainability. Based on our results, we recommend restricting pesticide use to periods of low pollinator activity and maintaining moderate shade levels (~ 50%).