Incidence-severity relationships in non-treated and fungicide-treated wheat head blast epidemics in Brazil

The relationship between wheat head blast incidence (I; proportion of diseased heads in a sample) and severity (S; the average area sample heads) was studied with aim determining whether could be reliably predicted from incidence. Data were collected two main sources: a) EPAMIG (non-treated) field experiments spanning seven years (2013–2019 three cultivars) designed to evaluate effect planting dates on (no fungicide use); b) UFTs (fungicide-treated) conducted by researchers network uniform trials during nine (2012–2020) across 10 locations (totaling 14 cultivars). An ordinary linear regression model fitted complementary log-log transformation data provided good fit based square correlation ?, observed S (R2): R2 0.95 for pooled (all years) non-treated dataset 0.88 fungicide-treated dataset. A covariance analysis indicated that year, but not cultivar, significantly affected parameters I-S We conclude can I more epidemics given larger influence chemical treatments than cultivar or surrogate varying weather.