Pesticides drive patterns of insect visitors and pollination-related attributes of four crops in Buea, Southwest Cameroon

The global decline in pollinators is driven by several factors including pesticide usage. This work investigated the effects of routine pesticide usage on the diversity of insect visitors and pollination-related attributes (yield and seed viability) of four crops: cucumber (Cucumis sativus : Cucurbitaceae), okra ( Abelmoschus esculentus : Malvaceae), soybeans (Glycine max : Fabaceae) and cowpea ( Vigna unguiculata : Fabaceae) in Buea, Southwest Cameroon. Using a randomized complete block design with two blocks of 16 experimental units each, pesticides were applied to half of the experimental units following routine famers practices. At flowering, insect visitors of flowers were collected using a net and preserved in 70% ethanol for identification under a stereomicroscope. The length, circumference and weigh of fruits were measured for cucumber and okra. The number of pods per plants of cowpea, the weight of cowpea and soybeans grains, the length of cowpea pods, and the number of beans per pods of cow pea were equally determined. Seed germination was determined by germination in Petri dishes under controlled conditions in the laboratory. Agrochemicals usage significantly reduced insect visitors’ abundance in the experimental plots of the four crops with a total abundance of 4316 and 1459, respectively for control and experimental plots independent of the crop type. Cucumber and okra yields were increased by pesticide application. The number of pods per plant of cowpea and the weight of cowpea and soybeans were significantly lower in the control plot. Using pesticides had a negative impact (F = 21.9; p < 0.001) on the length of pods in cowpea. The number of beans per pod of cowpea was significantly lowered (F = 43.6; p < 0.001) by pesticide application. Pesticide utilisation had a negative impact on seed viability of all the crops. These results underscore the need for proper pesticide regulation by decision makers and highlight the urgency to implement alternative methods to improve crop yield.