A multi-scale approach to study palm-weevils in a tropical agroecosystem

Abstract Context The recent phytosanitary crisis caused by the stem borer weevils Dynamis borassi and Rhynchophorus palmarum in peach palms (Bactris gasipaes) seriously affected the economy of local families in Colombia. To understand the possible ecological mechanisms favoring the pest, the weevil-palm system needs to be studied from a multi-scale perspective. Objectives We evaluated the combined effects of agricultural management, landscape, topography, soil, and climate variables on infestation levels of peach palm caused by the weevils D. borassi and R. palmarumin the Colombian southwest to understand underlying ecological drivers of the current phytosanitary crisis. Methods The palm infestation levels (response variable) and local agronomic practices were recorded in 32 sites across Colombia's Pacific, Andes, and Amazon natural regions. For each peach palm crop, landscape variables were estimated from classified Sentinel-2 images, soil variables were extracted from the Soil Grids 250 m database, and climate variables were extracted from the CHIRPS and CHIRTS databases. Explanatory variables were analyzed using Generalized Linear Models and Partial Least Squares-Generalized Linear Models. Results Landscape variables, specifically the number and shape of non-forest patches, had a greater influence on peach palm infestation levels than other environmental variables, possibly related to the decrease in the density of Oenocarpus batatua, the natural palm host for D. borassi, leading it to switch to the peach palm. Conclusions A multi-scale approach of the weevil-palm interaction enabled us to identify an ecological mechanism that has not been proposed before. Our recommendation for families depending on the palm is to design palm management with a landscape perspective that considers the conservation of alternative hosts for the weevils in agroforestal plots.