Estratégias de manejo químico no controle da ferrugem asiática da soja em diferentes épocas de semeadura ; Chemical management strategies without controlling asian soybean rust in different sowing times

Among the diseases that affect the soybean crop (Glycine max), Asian rust (Phakopsora pachyrizi) is one of the most relevant. The objective of this work was to evaluate the effect of the combination of fungicides and potassium phosphite, together with the genetic resistance of soybean cultivars sown at different times, on the severity of Asian rust and its impact on grain yield. The test was carried out at the Experimental Station of the Federal Technological University of Paraná, Campus Dois Vizinhos, in the 2019/2020 harvest. It had three sowing times (end of September, November and January) and two cultivars, TMG 7062 IPRO® INOX® (resistant to Asian rust) and NS 6909 IPRO® (susceptible). The products used were: Aproach prima (picoxystrobin + cyproconazole); Vessarya (picoxystrobin + benzovindiflupyr); Mancozeb (mancozeb); Reference (mancozeb + copper oxychloride) and Curative (potassium phosphite + copper and nickel). The treatments consisted of 35 management programs that differ in the combination of fungicides or fungicides + potassium phosphite, as well as timing (considering phenological stage) and number of applications (0, 2, 3, 4 and 5). A randomized complete block design with 3 replications was used. Disease incidence/severity, yield components and grain yield were evaluated. In September sowing, it was possible to verify that only two applications were enough to promote the control of Asian rust on soybean, for both cultivars, and that few treatments showed an increase in productivity in relation to the control. For November sowing, an increase in disease control was observed as the number of applications increased, for both cultivars, however, reduced numbers of applications, such as 2 and 3, were able to match in yield to treatments that received 4 and 5 applications, showing the possibility of obtaining greater economic viability with the sustainable use of fungicides. In January sowing, greater control was observed for both cultivars as the number of applications increased, however these results ...