A new multitrophic model for olive tree, olive fly and fly predators to support risk management in operational contexts

The production of olive (Olea europea) oil – a boast within Mediterranean agriculture – is periodically threatened by the olive fruit fly (Bactrocera oleae). The limited effectiveness of classical strategies for control of olive fly populations and related damages requires new solutions to support both prevention (e.g., early warning systems) and risk transfer (e.g., index-based insurance products). Biophysical models have been used successfully to reach these goals for a variety of cropping systems, but not to reproduce the olive tree-olive fruit fly multitrophic dynamics in operational contexts. We have developed a new model simulating olive tree (including key abiotic stressors), olive fruit fly (including its predators), and their interactions, specifically targeting on-farm applications. We integrated existing algorithms for each species with newly developed equations to improve the formalization of key biophysical processes. Model behaviour was assessed through sensitivity analysis and its performance evaluated under a wide range of agro-climatic conditions, using data on both olive tree growth and fly infestation. To our knowledge, this is the first time a model including a detailed simulation of the physiology of both species has been tested against observed fly damage (percentage of fruits infected). The good agreement between model outputs and observations (mean absolute error of 0.65 t ha−1, 0.87 t ha−1, and 5.4 % for, olive tree aboveground biomass, fruit dry mass, and percentage of fruits attacked, respectively) ‒ together with the parsimony in terms of model inputs – encourage its use to support olive tree growers in controlling this key pest.