Downy mildew is a highly destructive disease of grapevines caused by the oomycete Plasmopara viticola. It occurs in all grape growing regions with spring and summer rainfall above 10°C. The disease was first observed in the southeastern United States in 1834. Symptoms include yellow circular spots on leaves that later develop white downy fungal growth on the underside. Favorable conditions for the disease are temperatures between 64-76°F with high humidity. It can be managed through cultural practices like pruning and trellising as well as chemical fungicides.

1. COLLEGE OF AGRICUTURE BZU BHADUR SUB
CAMPUS LAYYAH
Downy mildew of grapes
Plasmopara viticola
By
M.Zeeshan
(Plant Pathology)

2. Introduction
Downy mildew is a highly destructive disease of
grapevines in all grape-growing areas of the world
where there is spring and summer rainfall at
temperatures above 10ºC (50ºF).

3. History
Plasmopara viticola was first observed in
Southeastern United States by Schweinitz in 1834 on
Vitis aestivalis.

4. Occurrence and distribution
• France, Europe, North America, Algeria, Australia
and all over grapes growing areas in World.

5. Symptoms on leaves
• Foliar symptoms appear as yellow circular spots with an oily
appearance (oilspots) on leaves.
• Young oilspots on young leaves are surrounded by a brownish-
yellow halo. This halo fades as the oilspot matures.
• Under favorable weather conditions, large numbers of oilspots
may develop and coalesce to cover most of the leaf surface.

6. • After suitably warm, humid nights, a white downy
fungal growth (sporangia) will appear on the underside
of the leaves and other infected plant parts.
• The disease gets its name "downy mildew" from the
presence of this downy growth.
• In late summer and early fall, the diseased leaves take
on a tapestry-like appearance when the growth of the
pathogen is restricted by the veinlets.

7. Life cycle
Ohionline.osu.edu

8. Taxonomic classification
Kingdom : Fungi
Superphylum
Class
Order
Family
: Heterokonta
:Oomycota
: Peronosporales
: Peronosporaceae
Genus
Species
:Plasmopara
: P. viticola

9. Favourable conditions
• Optimum temperature for disease development
is 64 to 76 F (18 to 25 °C).

10. Mode of spread
• Primary spread : Oospores on plant debris
• Secondary spread : Air borne sporangia

11. Management
Cultural practices:
• Well-drained sites with good air movement.
• Trellising systems and pruning can be used to
manage the leaf canopy to minimize leaf wetness
• Sanitation is important. Remove dead leaves and
berries from vines and the ground after leaf drop.

12. Chemical management
• Pre-infection fungicides include the copper-based
fungicides, such as Bordeaux mixture and the
Dithiocarbamates.
• Specific control for grapes downy mildew Cymoxanil,
fosetyl-al, metalaxyl, fenamidone, Sulfamide,
Mancozeb, Phosphonate, Azoxystrobin