SURVIVAL AND VIABILITY OF OVER WINTERING OOSPORES OF PLASMOPARA VITICOLA CAUSING DOWNY MILDEW IN GRAPES IN KASHMIR, INDIA

Downy mildew of grapes (Plasmopara viticola) is widespread and most destructive disease of grapes (Vitis vinifera L.) and has attained the status of a major disease of grapes under temperate conditions. The disease affects all the green parts of the vine namely leaves shoots, tendrils, inflorescence and bunches and is serious in climate with abundant rainfall, high humidity and longer periods of wetness on leaves and fruits. The pathogen perpetuates through winter in the form of oospores on fallen diseased leaves in/on floor of vineyards and in infected buds of pruned snags and intact shoots. The oospore production and their viability in soil decreased with increasing depth of placement of infected leaves Maximum oospore production in leaves located on the orchard floor is observed from the second fortnight of May to the first fortnight of June, while in buds of pruned snags, the maximum occurs from the first to the second fortnight of June. These infected leaves and buds of pruned snag lying on the ground served as the most significant overwintering sites for P. viticola