Identification, Description, Biology, Epidemiology, Treatement, Possible misleading, Images
Diffuse, pale, yellowish spots that become necrotic appear on the upper face of the leaves.
Olive coloured, downy tissue develops on the underside of the leaflet which then yellows.
The fungus remains viable under vegetable debris in the soil and on shelter structures.
The conidia are viable for 9 to 12 months. They are spread by wind, and air currents in shelters. They penetrate the plants through the stomata.
The incubation period is fairly long (12 to 15 days).
Sporulation occurs in several hours on the underside of the leaves.
The disease is found both in protected and field grown crops, near wind breaks for the latter.
Factors favourable to its development are temperatures ranging from 20 to 25 °C and a relative humidity greater than 80 %.
Use resistant varieties.
Pulverize a fungicide.
The fungal parasite Hansfordia pulvinata , may occasionally retard development of the disease.
HYP3 on line : Species (scientific name), Diseases (common names), Glossary, Crops.