Pollinator supplementation mitigates pollination deficits in smallholder avocado (Persea americana Mill.) production systems in Kenya

Abstract

Avocado (Persea americana Mill.) is a major horticultural crop that relies on insect mediated pollination. In avocado produc-tion, a knowledge gap exists as to the importance of insect pollination, especially in East African smallholder farms. In thisstudy, conducted in a leading smallholder avocado production region in Kenya, we assessed the dependence of avocado fruitset on insect pollination and whether current smallholder production systems suffer from a deficit in pollination services. Fur-thermore, we assessed if supplementation with colonies of the Western honey bee (Apis mellifera L.) to farms mitigated poten-tial pollination deficits. Our results revealed a very high reliance of avocado on insect pollinators, with a significantly lowerfruit set observed for self- and wind-pollinated (17.4%) or self-pollinated flowers (6.4%) in comparison with insect-pollinatedflowers (89.5%). We found a significant pollination deficit across farms, with hand-pollinated flowers on average producing20.7% more fruits than non-treated open flowers prior to fruit abortion. This pollination deficit could be compensated by thesupplementation of farms with A. mellifera colonies. Our findings suggest that pollination is limiting fruit set in avocado andthat A. Mellifera supplementation on farms is a potential option to increase fruit yield.© 2021 Published by Elsevier GmbH on behalf of Gesellschaft für Ökologie.Keywords: Fruit set; Fruit retention; Landscape composition; NDVI; Pollination services; Western honey beeIntroductionPollination is an essential ecosystem service for improvedquality and yield of crops, contributing to food security(Klein et al., 2007; Dainese et al., 2019). Currently, thedemand for pollination services in most pollinator-depen-dent crops is increasing (Aizen, Garibaldi, Cunningham, &Klein, 2009), and there is a need to incorporate insectpollination in sustainable agriculture systems to enhancefood security (Freitas et al., 2016). The economies of mostAfrican countries are heavily reliant on agricultural produc-tion, but the implementation of sustainable agriculture is asignificant challenge, and relatively few studies haveexplored the relationship between pollination and yields,especially in smallholder farming systems (Freitas et al.,2016).Using a global analysis based on 29 crops,Dainese et al. (2019) demonstrated increasing evidence of*Corresponding author.E-mail address: rsagwe@icipe.org (R.N. Sagwe).https://doi.org/10.1016/j.baae.2021.08.0131439-1791/© 2021 Published by Elsevier GmbH on behalf of Gesellschaft für Ökologie.Basic and Applied Ecology 56 (2021) 392 400 www.elsevier.com/locate/baae

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