Optimizing Fungicide Sprays to Tackle Powdery Mildew (Uncinula necator) At The Right Time For healthy grapes production

Introduction: Powdery mildew, caused by the fungus Uncinula necator, is a prevalent and harmful disease affecting grapevines, resulting in decreased fruit set and yield. This study aimed to evaluate the effectiveness of various fungicides and spray timings in managing U. necator in grape vineyards. Methods: A field trial was conducted in Pishin, Balochistan in 2020, employing a randomized complete block design with two factors: four fungicides (control, protective fungicide-Bordeaux mixture, curative fungicide-Elite 45 wp, systemic fungicide-Quintec) and four spray timings (dormant spray, bud break, one week before bloom, and berry formation). Results: The findings revealed significant variations in disease severity (PDI) among leaves, inflorescence, and bunches across different fungicides, spray timings, and their interactions. Application of the protective fungicide one week before bloom proved highly effective in preventing U. necator infection, resulting in the lowest PDI values for leaves (0.44%), inflorescence (0.67%), and bunches (0.0%). Curative fungicides sprayed at bloom stage also reduced PDI for inflorescence (2.17%) and bunches (3.56%). Systemic fungicides applied during berry formation exhibited lower PDI for inflorescence (6.44%) and bunches (4.0%) compared to other fungicides. The highest grape production (27.10 t ha-1) was achieved with the protective fungicide sprayed at bloom stage, followed by the curative fungicide at bloom stage (25.87 t ha-1). The negative and highly significant relationship (R2=0.809) between PDI of leaves and grape yield indicated that higher disease severity led to decreased yield. Conclusion: In conclusion, a protective fungicide spray before bloom, followed by a systemic fungicide spray at berry formation, effectively controls U. necator and ensures healthier and higher grape yields.