Cotton
Fusarium Wilt
Fusarium oxysporum
Fungus
In a Nutshell
- Wilting of plant.
- Yellowing of leaves.
- Inside of stem is stained brown or red.
Cotton
Symptoms
These fungi show crop-specific patterns of damage. In some cases, the plants show signs of wilting even at a juvenile stage, with leaves turning yellow. On mature plants, a slight wilting often appears on parts of the plants. This is most common during the warmest hours of the day. Leaves later start turning yellow, often only on one side. Longitudinal sections of the stems show a brownish-red discoloration of the internal tissues, first at the base, later up the stem.
Recommendations
Organic Control
Several biological control agents, including bacteria and nonpathogenic strains of F. oxysporum that compete with the pathogens, have been used to control Fusarium wilt in some crops. Trichoderma viride can also be used to treat the seeds (10g/kg seed). Some soils suppress the growth of Fusarium. Adjusting the soil pH to 6.5-7.0 and using nitrate rather than ammonium as nitrogen source can reduce the severity of the disease.
Chemical Control
Always consider an integrated approach with preventive measures together with biological treatments if available. Apply soil-based fungicides on contaminated locations if no other measures are effective. Drenching the soil with copper oxychloride (3g/l) of water before sowing/transplanting is also effective.
What caused it?
Fusarium wilt grows in the transport tissue of plants, affecting water and nutrient supply. Plants can be infected directly via their root tips or through wounds in the roots. Once the pathogen has become established in an area, it stays active for several years.
Preventive Measures
- Plant resistant varieties if available in your area.
- Adjust soil pH to 6.5-7.0 and use nitrate as nitrogen source.
- Monitor fields for signs of the disease.
- Handpick and remove affected plants.
- Keep your equipment clean, particularly when working between different fields.
- Avoid damage to the plants during field work.
- Apply a balanced fertilization with a special focus on the recommended potash.
- Plow and burn plant debris after harvest.
- Cover the infected area with black plastic foil in full sun for a month to kill the fungus.
- Plan rotations of up to 5-7 years to reduce levels of fungi in the soil.
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