Okra
Wet Rot
Choanephora cucurbitarum
Fungus
5 mins to read
In a Nutshell
- Appearance of water-soaked areas on leaves.
- Plant die-back.
- Occurrence of fungal growth.
- Affected young fruits, stems and flower buds.
Okra
Symptoms
Initial symptoms are characterized by a darkening and wilting of flowers, flower buds or growing points (blossom blight). The disease then spreads downward, producing water-soaked lesions on leaves, giving them a silvery tinge. Older lesions turn necrotic and appear dried out, resulting in blighted leaf tips and margins. On stems, signs of rot are visible in the form of brown to black patches and die-back. Eventually, the whole plant may wilt. Black soft rot can also develop on young fruits, usually at the blossom end. A close inspection will reveal silvery, hair-like growth on all infected tissues. In seedlings, symptoms may be confused with Phytophthora blight.
Recommendations
Organic Control
There is no biological treatment available for this disease. In Benin, the bacterium Bacillus subtilis has been tested positively in some crops for its antagonist effect against Choanephora cucurbitarum. However, no test on peppers has been carried out.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatments, if available. Prevention is the key as there are no fungicides labeled for this disease. Control using fungicides might help to restrict the development of symptoms but is often impractical because plants are continuously flowering and thus susceptible to the pathogen.
What caused it?
The symptoms are caused by Choanephora cucurbitarum, an opportunistic fungus that mainly attacks tissues that have been damaged by insects or mechanical means during fieldwork. Its spores are generally spread via wind, splashing water, and through clothes when in contact with tools and cultivation equipment. Outbreaks of the disease usually occur during prolonged rainy periods, high humidity and high temperatures. Not surprisingly, it causes the greatest damage to pepper and okra grown during the rainy season in tropical climates. Crop poorly adapted to these conditions will be particularly susceptible. In order to tell the difference with Phythophtora blight, observe tissues for the presence of grayish hairs (rather in the morning).
Preventive Measures
- Monitor fields for any signs of the disease.
- Remove alternative hosts and weeds in and around the field.
- Reduce soil compaction and improve drainage, if possible.
- Ensure no depression is left on the plant base during transplanting.
- Increase plant spacing and use raised beds and furrows.
- Avoid overhead irrigation and keep the leaves dry, if possible.
- Avoid the excessive use of nutrients that will create a dense canopy.
- Implement crop rotation with non-susceptible crops.
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