Important disease in cucumber, ridge gourd, sponge gourd, squash, muskmelons, pumpkins and other gourds.
Symptoms
Development of small yellowish areas on upper surface of the leaves. Later development of more brilliant yellow colour angular spots and restricted along veins. Purplish wet downy growth on lower surface of the leaves. Usually middle leaves are infected first followed by other leaves. The affected leaves die quickly. Rainy and humid weather favours the development of downy growth.
Disease cycle
It is an obligate parasite and survives on the diseased plant parts. Under unfavourable environmental conditions, the pathogen develop thick walled spores called as oospores which are resistant to dry conditions and low temperature. Moisture on leaf surface is necessary for the infection to occur. The pathogen infects large number of wild hosts along with cultivated crops.
Management
Sanitation and removal of infected plant parts.
Spray Veni GoKlean at the rate 1.25 to 1.5 ml per litre of water at 12-15 days intervals as preventative spray and or after recognition of the disease symptoms.