Pesticides, information, and pest management under uncertainty. Behavioral insights from Prospect Theory[Une analyse de la rationalité économique des choix des agriculteurs en matière de la protection fongicide du blé]

We analyze French farmers' fungicide protection of winter soft wheat for uncovering the rationality underlying their fungicide treatment decisions. Our analysis combine theoretical investigations based on recent theoretical work related to risky economic choices and empirical investigations based on data published by Arvalis, the French Technical Institute for cereal production. These data describe the fungicide protection choices of the "average French farmer" for the 2003 – 2019 period. Our main results are threefold. (a) Farmers' fungicide uses are close to the expected profit maximizing ones when disease risks are but they are significantly higher when the disease risks are low. (b) Two treatment protection programs appear to maximize expected profits in most considered years and seem to be considered as reference protection programs by the average French farmer. S/he easily adds a third, initially unexpected, treatment when the considered disease risk is higher than expected. But, s/he is reluctant to skip an initially planned treatment when the risk appear to be lower than expected. (c) These observations are nicely consistent to the predictions of the Prospect Theory of Kahneman and Tversky (1979) as complemented by Kőszegi and Rabin (2007). Making risky decisions in recurrent situations by considering the ones that are the most frequently optimal as benchmarks is intuitive, especially when these reference decisions significantly reduce loss risks. Turning down a relatively safe option in unusually low risk situations for a more profitable but riskier option is difficult for most decision makers, especially when the safe option is often optimal.