Control of tomato powdery mildew (Leveillula taurica) in the Comarca Lagunera, Coahuila State, Mexico, supported by the spray forecast model Tomato.PM

Tomato powdery mildew Leveillula taurica (Lev.) Arm.] is a common disease of tomato crops in the Comarca Lagunera region of the state of Coahuila, Mexico. To control the disease, fungicides are commonly sprayed up to 18 times on a weekly basis in this region. Effectiveness of the spray forecast model Tomato.PM, developed for California conditions, to reduce fungicide spraying, was evaluated. Disease dynamics on plants treated with three different fungicides (azoxystrobin, myclobutanil and wettable sulfur), with and without model recommendations, was analyzed in three experiments at three locations. When spraying followed model recommendations, it was possible to eliminate 11-16 fungicide applications with no significant effect on fruit yield. All three fungicides reduced the severity of disease but their effects varied with the cropping cycle. A significant increase in total yield due to fungicide spraying was observed in one out of three experiments.