Performance of Asian Soybean Rust Warning System at Different States in Brazil.

The Asian soybean rust (ASR) is controlled by sequential applications of fungicides following a calendar-based system. This approach considers only aspects of the crop, disregarding the influence of local weather conditions on disease progress. The aim of this study was to evaluate the performance of Asian warning system, based on precipitation data, in Brazil. The experiments were conducted at Piracicaba, SP (Lat. 22°42’ S, Long. 47°30’ W, Alt.: 546m), Ponta Grossa, PR (Lat. 25°05’ S, Long. 50°09’ W, Alt.: 969 m) and Campo Verde, MT (Lat. 15°24’ S, Long. 55°5’ W, Alt.: 689m.). The soybean sowings were done in 12^th December 2014 for Piracicaba and Campo Verde and 18^th December 2014 for Ponta Grossa, with row spacing of 0.45 m and plant population of 270 thousand plants per ha. The experiment was conducted in a randomized block design with four repetitions. The treatments were: 1) TEST - unsprayed check treatment; 2) CALEND - calendar-based sprays in a 14-day interval from R1 stage; T3) PREC system threshold 1 (50% severity cut-off). Fungicide used in all treatments was a commercial mixture (Azoxistrobina + Benzovindiflupir, 150 g per ha). Weather data were measured at an automatic weather station, located in the experimental area. For the three locations was observed that the TEST treatment exhibit higher disease levels and lower yield. Analyzing two methodologies for controlling Asian soybean rust, it was observed different sprays timing, probably due to different meteorological conditions. The better performance of the warning system was observed in Piracicaba and Ponta Grossa where reduced the number of sprays to control the ASR was observed (two and one spray less respectively). However, only at Ponta Grossa, this reduction increased the yields, with values greater than 440 kg ha^-1. In Campo Verde the warning system was not effective for controlling the disease.