Causal Agent:
Fungus (Cercospora citrullina)
| Characteristic Symptoms: | |
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Leaves and fruits can be affected particularly in hot humid conditions. |
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Leaf spots begin as small, round, brown lesions and often with white/light brown center. |
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Sometimes, spots are surrounded by a distinct yellow halo. |
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Under warm and wet conditions, the lesions expand and the leaves may appear blighted. |
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Fruit spots are small, circular and sunken. |
| Conditions for Disease Development: | |
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The disease is common in humid tropic and subtropical regions.
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The pathogen survives between crops on crop debris and weeds of the cucurbit family.
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The disease is common in heavy soils and in low-lying areas that can retain soil moisture for long periods. |
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Conidia/spores are air-borne and are disseminated by wind, rain splashes, tools/implements and field workers. |
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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.
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| Management and Control: | |
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Good field sanitation (i.e., remove and destroy infected plants/plant parts and cucurbit weed hosts) can help eliminate inoculum sources in the field.
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Crop rotation with non-cucurbit crops for 2-3 years will ensure elimination of inoculum in crop residues.
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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. |
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Use resistant varieties, if available.
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Disinfect tools used in an infested field with 10% household bleach (chlorox).
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Crop rotation with rice and corn for at least 3-5 years may help reduce inoculum in the soil.
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Use resistant/moderately resistant varieties, if available.
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| References: | |
| Compendium of Cucurbit Diseases (1996) by the American Phytopathological Society | |
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