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Quantifying the contribution of birds to the control of arthropod pests on kale, Brassica oleracea acephala, a key crop in East African highland farmland
Bird exclusion experiments on kale (Brassica sp.) plants were undertaken to quantify the extent to which foraging birds contributed to reducing the densities and impact of invertebrate pests. During the dry season, significantly higher leaf-area loss, aphid and thrips abundance were recorded in bird-excluded compared with control plants, suggesting that birds could make an important contribution to pest control. On average, per week, during the dry season, exclusion of birds from kale plants led to both a marked increase (130%) in the number of leaves
infested with aphids and an increase in leaf damage by pests (about three times greater than when birds had access to the kale plants). These results suggest that, in the dry season, foraging birds reduce the invertebrate pest load and hence the amount of leaf damage in kale, and that this may, in turn, have an impact of the market value of the crop. We recommend that measures to enhance avian insectivory should be explored and encouraged in order to better take advantage of birds in integrated pest management of kale and possibly other crops.