Chlorothalonil accelerates the photodecomposition of other pesticides exposed to sunlight on wax films

Objective: Just after foliar application, pesticides are exposed to solar light and can potentially undergo photodegradation. This photochemical reactivity affects the pesticide efficiency. Yet, these reactions are rarely studied. Another issue poorly considered is the potential mutual effects between pesticides. To improve crop protection, it is frequent to apply pesticides in mixtures or to use successively different pesticides during annual crop treatments. Mixing pesticides might have consequence on their photostability. Here, we investigated the fate of a mixture of two pesticides (the fungicide chlorothalonil and the herbicide cycloxydim) which have been already studied alone (1,2).