Background: Chayote is a crop traditionally cultivated in Réunion, but it is subject to numerous attacks by fruit flies, in particular Dacus ciliatus (Loew). During the last decade, experiments of agroecological management of fruit flies, in which farmers have been the central actors, have allowed to strongly limit the use of insecticides on chayote. In order to better support farmers in the management of fruit flies in their fields, a participatory approach aimed at designing and developing a model for predicting fruit fly injuries on chayote crops. Methods: From 2015 to 2018, observations were made on fruit fly injuries in different plots in Salazie, the main chayote production area in Réunion. These observations focused on different criteria: geographical location and altitude of the plots, cultivation practices, phytosanitary practices in general and on fruit flies in particular, farmers' practices in the vicinity of the plots, fly injuries. A qualitative model, based on the IPSIM approach, was designed and built in a collective manner, with farmers playing a central role in this process. The construction of the model, its evaluation, as well as the construction of a user-friendly online interface were carried out by research organizations (Cirad, INRAE). The assessment of this model was carried out with a large panel of farmers. Results: From the design of the model, farmers, agricultural advisors, trainers, public policy makers and researchers collaborated to define the conceptual scheme behind the IPSIM-chayote model that was developed. The fact that farmers were involved from the design phase of the model and that they were actors in the assessment phase allowed for their rapid appropriation and autonomous use of the tool. Farmers can now predict fruit fly injuries on their plots themselves; they can also improve their knowledge of the biology and ecology of fruit flies and of Agroecological Crop Protection practices. Extension organizations, such as the Cha