Field experiments were carried out at Ribeirão Preto and Pindorama, São Paulo State, Brazil, to evaluate the use of rainfall to predict the scheduling of fungicide applications to peanut early and late leaf spots control. Experiments were designed in completely randomized blocks with five replications. The following treatments were studied: (A) control, with no sprays to control leaf spots; (B) 4 sprays, on a 14-day application schedule, beginning at the 42nd day after planting; fungicide application after the occurrence of two (C), four (D) and six (E) days with daily rainfall > 2.5 mm, consecutive or not. The rainfall was monitored between 35th and 90th day after planting. The fungicide applications were made using chlorothalonil. Disease evaluations were made by a severity index, in leaflet samples at weekly intervals starting at the 30th day after planting. For each disease, disease severity was calculated by the area under the disease progress curve. A third variable was also obtained by adding the values of both diseases. The following evaluations were also made after harvesting and drying naturally: yield of unshelled peanuts kg.ha-1, shelling percentage and weight of 200 seeds. The results showed that the treatment: spraying after occurrence of 2 and 4 days with rainfall > 2.5 mm had the same performance as the 4-spraying treatment, considering disease severity and yield. These three treatments showed also better performance than those of the control and the treatment E. The occurrence of a high number of rainy days during the period of the study, allowed a reduction of only one spray for the treatment D as compared to the 4-spraying treatment, while the treatment C was similar to the control.
peanut; rainfall; leaf spot diseases; spray scheduling
