Meta-analytic modeling of the decline in performance of fungicides for managing soybean rust after a decade of use in Brazil

An apparent decline of the fungicide performance for the control of soybean rust in Brazil has been reported, but the rate at which it has occurred have not been formally quantified. Control efficacy and yield response to three fungicides applied as single a.i. [azoxystrobin (AZOX); cyproconazole (CYPR); tebuconazole (TEBU)] and four applied as mixtures [azoxystrobin + cyproconazole (AZOX+CYPR); picoxystrobin + cyproconazole (PICO+CYPR); pyraclostrobin + epoxiconazole (PYRA+EPOX)]; trifloxystrobin + prothioconazole (TRIF+PROT)] were summarized using network meta-analytic models fitted to mean severity and yield data from 250 trials (10-year period). The effect of year was tested on both variables in a meta-regression model. Overall control efficacy ranged from 56 to 84%; the three single a.i. fungicides performed the poorest (56 to 62%). Yield increase for single a.i fungicides were as lower as 30%, but ranged from 47 to 65% for the pre-mixes. Significant declines in both variables were detected for all f...