Stochastic modeling of yield losses due to bacterial leaf streak on corn

This study aimed to investigate the relationship between bacterial leaf streak (BLS) severity and corn yield based on four field experiments conducted under natural conditions with a total of 114 different corn hybrids in Paraná, Brazil, during the 2018 and 2019 growing seasons. A Monte Carlo simulation (n = 200 trials) was performed using empirical parameters derived from a linear mixed model fitted to the observed relationship between BLS severity and yield in the original trials. Each simulated trial included 50 corn hybrids, allowing for a robust estimation of yield losses and economic analysis under varying disease intensities. Power analysis was conducted using the linear mixed model to determine the minimum BLS severity threshold required to detect a significant impact on corn yield. This estimated threshold was then used to calculate the break-even probability of control treatment programs, considering variables such as attainable yield, yield loss rate, corn market price, treatment cost, and control efficacy under different disease pressure scenarios. Results showed that BLS severity can exceed 70%, with a mean of 13.3%, and significantly impacting yield. Corn yield averaged 8,964.1 kg/ha, ranging from 3,909.7 to 12,503.8 kg/ha across the evaluated hybrids. The estimated relative damage coefficient was 0.5%, meaning yield decreased by 5% per 10 percentage point increase in severity, with maximum yield reductions of up to 48% and economic losses reaching 1,220 USD/ha under a high disease severity scenario. Additionally, the power analysis demonstrated that a BLS severity of approximately 25% (14% yield loss) enables robust detection of its impact on corn yield. Simulating the use of a control treatment showed substantial yield protection (up to 1,552 kg/ha) and economic returns (up to 100%) across all treatment cost and control efficacy scenarios when disease pressure was high (>25%), compared to low-pressure conditions (≤25%). These findings underscore the agronomic and economic impact of BLS, establish a severity threshold for selecting tolerant corn hybrids in breeding programs, and provide a profitability framework for disease management in the field.