Plasmopara viticola ia an obligate parasite and the sexual reproduction spores are Oospores (survival spores-decayed leaves in soil). The asexual reproduction spores are called Zoospores. It is a severe fungal disease and the optimum conditions are winter-wet and spring-warm rainy summer. Spread through the wind (conidia) and rain. The pathogen survives in leaf debris (soil) or diseased shoots. Symptoms of downy mildew may be confused with powdery mildew spots, in early stages.
Leaves: Oilspots. White cottony fungal growth on the underside of leaf on the oilspots(warm/humid night). Oilspots became necrotic and may proceed to defoliation
Stem: Shoots takes an S form with oil brown areas sometimes covered with white fungal growth
Fruits: Brown discoloration and shrinkage of berries
Flowers: Inflorescences are covered with white fungal growth
Hosts: Vitis vinifera, other vitis varieties
“Diseases of fruit trees and grapevine”- Panagopoulos G.C
Department of Primary Industries and Regional Development’s Agriculture and Food division- Government of Western Australia, Downy Mildew of Grapes