Responsividade de cultivares de soja ao controle químico da mancha alvo

Abstract

Target spot, caused by the fungus Corynespora cassiicola, is one of the most important soybean diseases. Target spot control relies on fungicide application, but inconsistent results regarding grain yield increase have been noticed. Cultivar susceptibility may influence fungicide response. In order to fill this gap, two experiments were carried out in two seasons (2019/2020 and 2020/2021) aiming at investigate cultivar responsiveness to fungicide application. Experiments were carried out in completely randomized design with four replications. First experiment, which was carried out in season 2019/2020, was arranged in a 8 × 3 experimental design, with eight cultivars and three foliar treatments. The cultivars were as they follow: Syn 1258 RR, M6410 IPRO, M5947 IPRO, NA 5909 RG, BS 2606 IPRO, Syn 1059 RR, BMX Garra IPRO e BMX Delta IPRO. In season 2020/2021, a 20 × 3 factorial design was used, with 20 cultivars and three foliar treatments. The following cultivars were assessed: NA 5909 RG, BMX Lótus IPRO, 96R10 IPRO, 96Y90, TMG 7063 IPRO, BMX Garra IPRO, BMX Potência RR, BMX Fibra IPRO, 95R95 IPRO, M6210 IPRO, BS 2606 IPRO, M6410 IPRO, Syn 1258 RR, 96R29 IPRO, Syn 1059 RR, DM 6563 IPRO, BMX Delta IPRO, Syn 15630 IPRO, HO Pirapó IPRO and M5947 IPRO. In both seasons, foliar treatments consisted in a control without fungicide (T1) and two (T2) or four (T3) fungicide applications. Fungicides were applied fortnightly and apllications were started at 35 and 65 days after emergence for T3 and T2, respectively. Target spot severity and grain yield were determined. Data were subjected to the analysis of variance (ANOVA) and the means of the treatments were compared by the Tukey’s test (P≤0,05), using the software Minitab. In general, four applications outperformed two applications and susceptible cultivars, including BMX Garra IPRO, were more responsive to fungicide application. In conclusion, our results evidence the central role that soybean cultivars have in the determination of control programs of target spot.