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Research article2019Peer reviewedOpen access

Shade trees decrease pest abundances on brassica crops in Kenya

Guenat, Solene; Kaartinen, Riikka; Jonsson, Mattias


Agroforestry practices may mitigate the current loss of biodiversity and ecosystem services due to deforestation and agricultural intensification. To examine the effects of agroforestry on the ecosystem service of pest regulation, we assessed pest abundances and biological control potential in shaded and open kale (Brassica oleracea L. acephala) fields in Western Kenya. Specifically, we compared the abundance of pest aphids and caterpillars, ground-dwelling ants, spiders and predatory beetles, and examined aphid parasitism rates, predation rates on diamondback moth eggs, attack rates on surrogate caterpillars and bird predation on aphids. Shade trees effectively reduced abundances of aphids, caterpillars and increased abundances of spiders and predatory beetles, but neither affected ant abundances, or predation and parasitism rates. Our results suggest that presence of shade trees can decrease pest abundances, but that this is not only due to improved biological control by natural enemies but also due to microclimatic conditions affecting pest performance and bottom-up processes such as changes in plant quality and soil conditions. We encourage studies exploring simultaneously how top-down and bottom-up processes affect pest regulation in agroforestry settings.


Agroforestry; Aphids; Pest control; Brassica olearacea var; acephala; Parasitism; Predation

Published in

Agroforestry Systems
2019, Volume: 93, number: 2, pages: 641-652
Publisher: SPRINGER

      SLU Authors

    • Associated SLU-program

      SLU Plant Protection Network

      Sustainable Development Goals

      SDG15 Life on land

      UKÄ Subject classification

      Agricultural Science

      Publication identifier


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