Mycologia,MASTIGOMYCOTINA, PERONOSPORALES, PERONOSPORACEAE .
Identification, Description, Biology, Epidemiology, Treatement, Possible misleading, Images
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.
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.
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.
Ensure minimum crop rotation every three years.
Drain the soil.
Use resistant cultivars.
HYP3 on line : Species (scientific name), Diseases (common names), Glossary, Crops.