Yield Loss in Sweet Corn Caused by Puccinia sorghi: A Meta-Analysis

Data sets meeting established criteria were included in a meta-analysis of the relationship between percent common rust severity and percent relative yield loss in sweet corn (processing: 20 data sets; fresh market: 14 data sets). The slope of the linear, zero intercept relationship was estimated from each data set. Overall slopes and their respective 95% confidence intervals for the processing and fresh market situations were estimated by a random effects meta-analysis. Results indicated that for processing sweet corn, every 10% increase in rust severity reduced yield by 2.4 to 7.0%; the corresponding reduction for fresh market sweet corn was between 3.0 and 6.2%. A meta-regression analysis did not identify any factors that could account for the observed variability between data sets. An expression was then obtained for Δ_s, the reduction in rust severity a single strobilurin fungicide spray ought to cause for the cost of the treatment to be offset by the value of the resulting yield improvement. The empirical distribution of Δ_s,was derived by stochastic simulation, which showed that fungicide usage could be cost effective 90% of the time when rust severity is reduced by 12% in processing sweet corn and by 5% in fresh market sweet corn.