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Mycologia,MASTIGOMYCOTINA, PERONOSPORALES, PERONOSPORACEAE .

Crops attacked: spinach .

Downy mildew

Identification, Description, Biology, Epidemiology, Treatement, Possible misleading, Images

[R]Description
In autumn, pale, round (1 - 2 cm diameter) spots occur on the upper surface of the leaves.
The lower surface is covered by a purplish-white down.
On the older leaves yellow lesions occur.
The infected plants are unmarketable, their taste is altered even when used as canned food.

[R]Biology
The fungus survives as oospores in the soil or as mycelium in the seeds. The infected plants produce sporangia on their lower surface which can infect other neighbouring plants.

[R]Epidemiology
The disease mainly develops in mild, humid (dew) conditions, in young plants.
Sporulation and germination of sporangia occur between 9 and 12 °C. Seedlings are easily infected ; adult plants are susceptible to infection on the growing point if free water is present for at least 6 hours.

[R]Treatement
Ensure minimum crop rotation every three years.
Drain the soil.
Use resistant cultivars.

[R]Possible misleading
.

[R] Images

1. Peronospora spinaciae , Spinach downy mildew (ROUXEL F., INRA)
   Spinach downy mildew Spots of downy mildew on leaves of spinach.
   
2. Peronospora spinaciae , Spinach downy mildew (BASF)
   Spinach downy mildew Downy cover of downy mildew on the leaves of spinach.
   

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