Causal Agent: 

Fungus (Cercospora citrullina)

Characteristic Symptoms:
Leaves and fruits can be affected particularly in hot humid conditions.
Leaf spots begin as small, round, brown lesions and often with white/light brown center.
Sometimes, spots are surrounded by a distinct yellow halo.
Under warm and wet conditions, the lesions expand and the leaves may appear blighted.
Fruit spots are small, circular and sunken.
Conditions for Disease Development:
The disease is common in humid tropic and subtropical regions.
The pathogen survives between crops on crop debris and weeds of the cucurbit family.
The disease is common in heavy soils and in low-lying areas that can retain soil moisture for long periods.
Conidia/spores are air-borne and are disseminated by wind, rain splashes, tools/implements and field workers.
Infection requires free water and is favoured by temperatures between 26-32°C, in which the disease develops rapidly with new infections occurring every 7-10 days.
Management and Control:
Good field sanitation (i.e., remove and destroy infected plants/plant parts and cucurbit weed hosts) can help eliminate inoculum sources in the field.
Crop rotation with non-cucurbit crops for 2-3 years will ensure elimination of inoculum in crop residues.
A regular fungicide spray program of copper-based fungicides (e.g. Cupravit®, Super BlueⓇ, Vitigran blueⓇ, FunguranⓇ, KocideⓇ, Hydroxide superⓇ) and  chlorothalonil (e.g. Daconil®, Agronil®, Yoda®, Rover®, Yoda 500Ⓡ) may help reduce incidence and severity especially when crops are susceptible and conditions are favorable for disease development.
Use resistant varieties, if available.
Disinfect tools used in an infested field with 10% household bleach (chlorox).
Crop rotation with rice and corn for at least 3-5 years may help reduce inoculum in the soil.
Use resistant/moderately resistant varieties, if available.
Compendium of Cucurbit Diseases (1996) by the American Phytopathological Society

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