The effects of shade, altitude and landscape composition on coffee pests in East Africawca2014-2494 Mattias Jonsson 1,*Ijala A. Raphael 2Nina Backlund 3Louise Malmberg 3Jeninah Karungi-Tumutegyereize 2Samuel Kyamanywa 2Barbara Ekbom 1 1Swedish University of Agricultural Sciences, Uppsala, Sweden, 2Makerere University, Kampala, Uganda, 3Lund University, Lund, Sweden
The diversity and abundance of natural enemies of insect pests is often higher in agroforestry plantations than in sun-exposed monocultures, and it is often assumed that this will result in improved pest suppression. However, the effect that incorporating trees in cropping systems will have on pest populations also depends on the habitat requirements of the pests themselves. We studied how the abundance of a range of coffee pests was influenced by agroforestry in East Africa. Along the slope of Mt Elgon in Uganda we studied how shade level and altitude influenced the abundance of the white stemborer, Monochamus leuconotus, and the coffee berry borer, Hypothenemus hampei, and close to Kitale in western Kenya we investigated how various pests on coffee leaves, e.g., aphids and lacebugs, were influenced by shade level and the amount of trees in the surrounding landscape. We found that the effect of shade trees differed between pest species. The coffee berry borer was more common on sun-exposed plantations, whereas the white stemborer was more common in shaded plantations. However, the effect of shade level on the white stem borer depended on altitude, with the differences between shade levels being most pronounced in plantations at low altitudes. For lacebugs, Habrochila ghesquierei and Habrochila placida, the effect of shade trees depended on the amount of trees present in the surrounding landscape, with a higher abundance of lacebugs in shaded plantations only in landscapes with a low tree cover. The results from this work show that the impact of agroforestry on pest regulation in coffee is highly context specific; it depends on the identity of the most important pests in the area, the altitude and landscape composition.