Influence of Pruning Seasons and Weather Parameters on Powdery Mildew (Erysiphe necator Schw.) Disease Incidence of Grapes (Vitis vinifera L.) var. Muscat Hamburg

Abstract

Grapes (Vitis vinifera L) powdery mildew caused by the obligate fungus Erysiphe necator Schw. is one of the most important diseases causing considerable losses in grapes. The incidence of powdery mildew disease was assessed from July, 2022 to April, 2023 at Grapes Research Station, Anaimalayanpatty, Theni at weekly interval revealed that the highest incidence of 62.73 per cent was observed during second week of October, 2022 after summer pruning, which coincides after harvest period. Similarly, the disease incidence of 66.26 per cent was noticed during second week of February, 2023 after winter pruning which coincided in the fruiting period. Correlation studies with weather parameters on disease incidence revealed that maximum temperature (0.670^**), sunshine hours (0.513^*) and soil temperature (0.604^**) registered significantly positive correlation on powdery mildew incidence whereas average relative humidity reported with significant negative correlation (-0.602^*) both during summer and winter pruning. Further, disease incidence was positively correlated with wind velocity (0.476^*) after winter pruning. Rainfall was negatively correlated for powdery mildew disease incidence both summer and winter pruning.