The effects of shading and surrounding landscape composition on arthropod pest abundance in Coffea arabica plantations

In agriculture plantations surrounded by complex landscapes often harbour higher abundance and diversity of natural enemies compared with plantations in simple landscapes. However it is unsure if the landscape effect on natural enemies cascade down and influence pest abundances. In this field study, our goal was to examine the importance and potential interactions between landscape composition and local habitat management. To do so, we compared arthropod pest abundances in sun-exposed and shaded plantations of Coffea arabica in Western Kenya.
 
The study was conducted in cooperation with Swedish University of Agricultural Sciences (SLU) and the Vi-agroforestry programme (a non-governmental organisation). In addition to the pest survey a tree inventory and interviews with farmers and the governmental organisation Coffee Research Foundation (CRF) was conducted in order to compare the CRF recommendations with the farmer’s perspective. In total 36 different tree species (including banana) was found in the coffee plantations, however most of these occurred in very low numbers. Grevillea robusta was the most common tree species found. In general the coffee farmers did not consider insects as a major problem in their coffee production. Most of the farmers considered shade being beneficial for the coffee and many sold gods that the trees provided and planted food intercrops within the coffee plantations.

Based on the interview CRF appeared to have quite negative attitude towards coffee agroforestry and intercropping. As diversifying incomes has been proposed as a climate adaption and poverty reduction strategy I suggest a stronger cooperation between the Vi- agroforestry programme and CRF. A lot could be gained by sharing knowledge and developing a common framework for the coffee production in this region. The pest survey revealed that there was significantly higher abundance of lace bugs in shaded sites. In contrast shade had no significant main effect on aphid or leafminer abundance. Landscape composition did not show a significant main effect on the abundance of the pests. However there was a non-significant trend towards higher abundance of leafminers and lace bugs in sites surrounded by more complex landscapes. The interaction between local management and proportion of tree cover in the landscape was significant for lace bugs, for leafminers the interaction between local management and proportion of semi-natural habitat was significant and for aphids both these interactions were significant. Three of these four interactions indicate that local shading has the highest effect in simple landscapes. The results clearly highlight the need to consider both local management and landscape management when designing pest suppressive and sustainable agricultural environments.
 
Backlund, N. (2012). The effects of shading and surrounding landscape composition on arthropod pest abundance in Coffea arabica plantations. Master’s Thesis. Lund University.
 
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