An integrated pest and pollinator management approach for smallholder avocado (Persea americana Mill.) farms under different landscape contexts

Abstract

Insect pest infestation is one of the common threats in cropping systems that reduces yield and endangers food security worldwide. Adoption of an environmentally friendly pest management approach is being widely encouraged to suppress pests with minimum negative effects on the environment and biodiversity. Besides, concerns for adequate crop pollination have recently increased because of the current global pollinator crisis. However, these two services (pest control and pollination enhancement) that support crop production have been studied in isolation, with little investigations into their potential interaction on crop yield. This thesis explores ways of enhancing pollination for integration with pest management practices to increase the productivity of avocado (Persea americana Mill.) (Lauraceae) within smallholder farms, and the use of flower strips to support pollinators in a commercial avocado orchard in Kenya. Specifically, the spatial distribution of major avocado pests; the oriental fruit fly Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) and false codling moth Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), and associated parasitoids were investigated across landscape vegetation productivity classes, using the normalised difference vegetation index (NDVI) from Sentinel-2 satellite data. Pest abundances were found to vary among landscape classes, with higher abundances in the low and medium vegetation productivity classes than in the high class. Parasitoids reared from infested fruits provided some insights on their potential use in biological pest control programs. The impacts and potential interactions between integrated pest management (IPM) and the introduction of managed honey bee colonies under a strategy called integrated pest and pollinator management (IPPM), were assessed on avocado pests, pollinators and productivity across landscape vegetation productivity classes. The abundance of Apis mellifera L. (Hymenoptera: Apidae) was shown to be influenced by the interactions between landscape vegetation productivity and IPM. Neither IPM nor the introduction of managed honey bee colonies represented a threat to non-Apis flower visitors. In addition, the IPPM strategy resulted in a 941% of fruit set increase and up to 97% of fruit abscission within the high vegetation productivity class. The abundance of B. dorsalis and T. leucotreta significantly decreased on the farms with IPM, resulting in a 6% increase of final fruit weight compared with the farms without IPM. To support avocado pollinators other than A. mellifera, the effectiveness of the flower strip mixture in increasing pollinator abundance and fruit set was investigated. Results revealed lower abundances of A. mellifera and syrphid pollinators on plots with flower strips compared with plots without, resulting in a comparable fruit set between the treatments. Overall, this thesis supported the hypothesis that IPM reduced pest abundances, increased fruit weight, and did not negatively affect avocado pollinators. However, the IPPM strategy did not significantly increase yield but could provide additional incomes through beekeeping products, or provision of pollinator resources and pest biological control when combining the IPPM strategy with flower strips. Future studies on ecological mechanisms that shape the effects of IPPM strategy will help provide better tools to farmers and policymakers on sustainable and cost-effective farming practices that increase qualitative and quantitative avocado yield.