Climate risk of Asian soybean rust occurrence in the state of Rio Grande do Sul, Brazil

One of the greatest challenges for the sustainability of soybean production in Brazil is the control of Asian soybean rust (ASR). This study aimed to assess the climate risk of ASR occurrence throughout the period recommended for sowing in four locations of Rio Grande do Sul, considering different soybean relative maturity groups and the phases of the El Nino–Southern Oscillation phenomenon. The soybean development cycle and the climate favorability for ASR occurrence were simulated for the recommended sowing dates in the period from 1961 to 2020 in four locations of Rio Grande do Sul. Early cultivars, sown at the beginning of the period recommended by Agricultural Zoning of Climate Risk, usually exhibit less favorable climate conditions for ASR occurrence and less interannual variability in their cycle. The effect of the El Nino/Southern Oscillation phenomenon varies across the studied locations, with the prevalence of more favorable conditions for ASR occurrence during El Nino years. However, neutral years show greater interannual variability for the risk of ASR occurrence.