Association phosphite x fungicide: protection against powdery mildew in soybean plants, translocation and computer simulation

Phosphites have been used to control several soybean diseases, however, few studies have investigated the association between phosphites with fungicides in soybean. The objectives of this study were to assess the potential of potassium phosphite (Phi) in combination with fungicides for powdery mildew management, and Phi detection in the presence of fungicide through colorimetry. In addition computational calculations were performed to verify the Phi–fungicide interactions. The first experiment assessed powdery mildew severity in soybean using the following treatments: prothioconazole + trifloxystrobin (Pro + Tri), azoxystrobin + benzovindiflupyr (Azo + Ben), and the combinations of the fungicides with Phi applied only to the fourth trifoliate leaves or the whole plant. In the second experiment, Phi translocation was evaluated in plants sprayed with Phi, Azo + Ben, and Azo + Ben + Phi. In addition, computational calculations were performed to investigate the phosphite–fungicide interaction. The Phi and fungicide combination reduced disease severity and increased Phi concentrations in all leaves analyzed. Possible interaction between the Phi and fungicide was verified by computational calculations, especially Phi + benzovindiflupyr.