Strategic free-riding in pest control: Theory and evidence in organic-conventional mixed landscapes[Le parasitisme stratégique dans la lutte contre les ravageurs : théorie et données empiriques dans les paysages mixtes (agriculture biologique et conventionnelle)]

Organic and conventional farmers face the same pests but differ in technologies and economic incentives to control them. This paper theoretically and empirically characterizes the strategic interactions for pest control between these two types of farmers within mixed organic-conventional landscapes. Our non-cooperative game model shows that each farmer type is expected to strategically free-ride on the other's control efforts when managing a sufficiently small share of the landscape, and that the extent of free-riding increases with lower pest pressure, higher relative treatment costs, and lower treatment efficacy. Using exhaustive French postcode-level data on insecticide purchases against the vector of a vine disease (Flavescence dorée), we provide empirical support for all our theoretical propositions. Our preferred estimates indicate that organic farmers free-ride on conventional farmers' efforts until they reach about 8% of the landscape. Beyond this threshold, organic treatments only partially substitute for reduced conventional treatments, up to a point where conventional farmers may eventually free-ride if the organic landscape share becomes large enough. Consistent with the model's predictions, high pest pressure substantially reduces the scope for free-riding, while differences in relative treatment costs and treatment efficacy also affect its extent, though to a lesser degree.