Causal Agent:
Fungus (Sclerotium rolfsii)
| Characteristic Symptoms: | |
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The pathogen attacks mainly the stem near the ground and the most common symptom is the brown to black rot or sunken tissues of the stem near the soil line, which often lead to wilting and death of the plant. |
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Under moist conditions, mass of white thread-like mycelia develop on the lesion often girdling the stem base and mustard-size light tan to reddish brown, hard and round sclerotia are embedded in the mycelia. |
| Conditions for Disease Development: | |
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The fungus infects many crops, including solanaceous, cucurbits, legumes and onions.
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The pathogen produces sclerotia, which can survive in the soil for long periods when soil moisture is low.
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Periods of hot, humid weather favor disease development |
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Infection can either be direct or through wounds created by nematodes or insects.
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Germinating sclerotia may also infect fruit, leaves and branches that touch the soil.
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The fungus is spread into a field by infested soil or cultivating tools, infected transplants, running water, and as sclerotia mixed with seeds.
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| Management and Control: | |
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Avoid dense planting and choose fields which are well-drained and not too acidic.
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Bury crop debris to a depth of 24 cm to suppress germination of sclerotia. |
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Application of ammonium nitrate before planting or as side dress can help reduce incidence.
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In new or unaffected areas, crop rotation with non-hosts like corn maybe effective in reducing inoculum in the soil.
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protect seedlings by drenching with chemical fungicides like difenoconazole (e.g. ScoreⓇ, MontanaⓇ, PursueⓇ, BashⓇ), Pyraclostrobin (e.g. Cabrio 25 ECⓇ), metalaxyl+mancozeb (e.g. Ridomil Gold MZ 68 WGⓇ, Apron XL 350 ESⓇ) or carbendazim ( (Bavistin 50 DFⓇ, Goldazim 500 SSⓇ, Minx 500 SCⓇ, SuperdazimⓇ, Avert 50 WPⓇ, BiostinⓇ). |
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