Timing of triazole-based spray schedules for controlling mungbean powdery mildew in Australia: a meta-analysis.

Abstract Powdery mildew (PM), caused by two fungal species, Podosphaera xanthii and Erysiphe vignae , is a yield limiting foliar disease commonly found in mungbean ( Vigna radiata) cropping areas of eastern region of Australia. Effective control of PM afflicting mungbeans relies largely on fungicide applications, mainly of the triazole group. Uncertainty in the current fungicide spray schedule recommendations, which advise commencing with a spray at the first sign of PM, prompted this study to evaluate PM severity and crop yield data obtained from fungicide trials which tested spray schedules starting before ( Early ) or after ( Late ) first signs, applied singly or combined with a follow-up spray. A meta-analytic approach was employed to obtain estimates of the yield and PM severity difference between plots sprayed with specific triazole-based sprays schedules and untreated plots. From 26 trials, 15 and 14 met the criteria for inclusion in the yield and PM severity analysis respectively. The schedule with the first spray starting at first sign with a follow-up spray 14 days later, resulted in significantly lower disease severity compared to all other schedules, however, the yield protected was only numerically higher and not statistically different compared to: single-spray at first sign, single-spray Late or two-spray starting Late . While PM severity was lower in the Early sprayed plots compared to untreated plots, yield did not differ. These findings support the current recommendations and provide evidence that the first spray could be delayed up to a week and save an additional spray that may be unnecessary, thus reducing direct fungicide costs as well as indirect costs due to fungicide resistance.