Cotton
Fungal Boll Rot Complex
Fusarium/Aspergillus/Phytophthora/Rhizopus/Diplodia
Fungus
In a Nutshell
- Dark discoloration and softening on bolls.
- Premature opening and falling of cotton bolls.
Can also be found in
Cotton
Symptoms
Fungal boll rot in cotton is marked by a progression of symptoms. Initially, small brown or black spots appear on the young green cotton bolls, which then expand to cover the entire boll. The affected bolls turn dark brown to black, soften, and may appear water-soaked. As the disease progresses, it penetrates the inner tissues, decaying the seeds and lint. In severe cases, the fungus can cause premature opening of the bolls, resulting in stained and degraded cotton fibres. In humid conditions, visible fungal growth may occur on the bolls.
Recommendations
Organic Control
It's challenging to fully control cotton boll rot using only organic and biological methods. Researchers are exploring options like Trichoderma viride, but it's not yet available for commercial use.
Chemical Control
Start by applying copper oxychloride and mancozeb as sprays on the leaves and seeds to block disease spread. Also, mix fluxapyroxad and pyraclostrobin in a suspension concentrate to fight various pathogens. Apply this mixture when you first notice the disease and repeat the treatment after 15 days for thorough control. When using pesticides or any chemical product, it is important to wear protective clothing and carefully read the label instructions. Regulations vary by country, so ensure you follow the specific guidelines for your area. This guarantees safety and increases the chances of successful application.
What caused it?
Cotton boll rot is caused by various fungi in the soil and seeds. Factors like too much nitrogen, too much water, rain, and high humidity increase the risk. The disease is more likely in unopened bolls at the bottom of the plant and usually appears about 100 days after sowing. Fungi and bacteria enter through cracks or injuries on the boll, often made by insects like bollworms and Red Cotton Bug. The disease can also spread through airborne fungal spores produced by the fungi on the infected bolls.
Preventive Measures
- Using healthy seeds.
- Avoid excess nitrogen application and irrigate properly.
- Avoid late sowing.
- Adopt wider spacing.
- Regularly check mature bolls in the lower part of the plants for symptoms during the rainy season.
- Controlling insects such as bollworm and Red Cotton bug has their own importance but is significant in this case too.
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