- Usually central leaves are affected first followed by other leaves until the entire plant is wilted.
- Young leaves are less susceptible. Infection occurs more rapidly on lower surface.
- The first symptom on the leaves resemble those of mosaic mottling.
- The fungus cause pale yellowish, angular patches on the leaves often restricted by veins on the upper surface.
- Gradually the spots turn dark brown and dry up.White downy growth of the fungus is visibleon the lower surface of the affected leaves during humid conditions.
- During the later stages, the entire leaves are affected and may turn yellow, decay and fall off.
- On infected plants fruits are few, small with poor taste.
The maximum sporangial dispersal occurs during morning. Cucumber beetles are known to carry sporangia from one plant to another. The disease spreads in fields through dispersal of sporangia by rain drop splashes and beetles. Low nutritional status predisposes the plants to infection.
Randomly mark five one square meter area from the plot. From each square meter select 5 leaves at random and record the incidence of the disease.Count the leaves showing symptoms (even if a spot is present that leaf is considered as infected). Work out the average leaves showing infection.