INFLUENCE OF FUNGICIDES AND POTASSIUM PHOSPHITE ON ASIAN RUST AND YIELD OF SOYBEAN

This study evaluated the effects fungicides with or without association with potassium phosphite on the control of the Asian rust (Phakopsora pachyrhizi) of soybean. Two field tests('Coodetec-219RR' and 'Emgopa-313') were conducted (12/2005-4/2006) in Cristalina (Goias, Brazil), in a complete randomized block design (Nine treatments; five replications). The treatments were with one and two applications of phosphite-K (1192 g a.i. ha(-1) P2O5 + 596 g a.i. ha(-1) K2O) + vegetable oil (VO - 0.5% v v(-1)), two applications of traditional fungicides (TF) [pyraclostrobin+epoxyconazole (66.5 + 25 g a.i. ha(-1)); methylthiophanate+flutriafol (300+60 g a.i. ha(-1)); tebuconazole (100 g a.i. ha(-1))], and, one application of TF+phosphite and a second application of phosphite+VO. For 'Emgopa-313', product applications were made on V8 and R2 soybean growth stage, while for Coodetec-219RR on R1 and R5. Evaluations of disease severity (%DS) were made each seven days after product applications. After the first product application, all treatments significantly reduced DS. At the end of evaluations only treatments with TF significantly reduced DS. Yield and mass of 1000 seeds were significantly higher for treatments with TF. Phosphite-K applications decreased DS, but did not increase yield and mass of 1000 soybean-seeds.