Relationship between soybean plant defoliation and Asian soybean rust severity

ABSTRACT Data from experiments conducted in the field with eight fungicide mixtures added of five mancozeb levels were used to generate gradients of soybean rust severity, plant defoliation, and soybean grain yield. The data were subjected to correlation analysis between defoliation and severity, defoliation and grain yield, and grain yield and rust severity. All correlations were significant, evidencing a relationship between variables. Analyses conducted in other studies have shown that severity control has greater influence on decision-making, compared to defoliation. Therefore, as defoliation is dependent on severity, evaluation of rust intensity is sufficient, suggesting that defoliation can be excluded from evaluation for this pathosystem.