Cotton has been cultivated for thousands of years and remains a cornerstone of the global textile industry. Its soft fibers, derived from the cotton plant's bolls, are spun into yarn and fabric, making it essential for clothing, home textiles, and industrial products. Cultivated primarily in warm climates, cotton thrives in regions with ample sunlight and moderate rainfall. The plant itself is a perennial shrub that can grow up to 6 feet tall, showcasing beautiful yellow flowers that eventually transform into fluffy white balls.
Different Diseases of Cotton With their Remedies
1. Bacterial Leaf Blight: The bacterial blight caused by Xanthomonas citri is a major disease of cotton. It occurs between seedling to boll development stages. Symptoms include water soaked, angular leaf spots from lower leaves to stem.
Remedies
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Cotton seeds should be delinted with concentrated sulphuric acid at 100 ml/kg of seed.
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Delinted seeds should be treated with Carboxin or Oxycarboxin at 2 g/kg or Carboxin 37.5% + Thiram 37.5% WS @2.5 g/ kg
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Infected plant debris should be removed and destroyed.
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Early thinning and early earthing up should be done with the help of the potash.
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Streptomycin Sulphate should be sprayed @ 100g +Copper oxychloride@500 g/acre.
2. Bronze Wilt: This disease can affect the plant at any growth stage, but it is particularly prevalent during the boll development phase. Symptoms include coppery discoloration on the top leaves, red wilt, sudden wilting, or phloem wilt in the plant. Even if the upper taproot and lower stem seem healthy, signs of wilting are seen throughout the plant.
Remedies
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Crops sowing should be done early to prevent high soil temperatures during fruiting.
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Application of necessary amounts of nitrogen fertilizer can meet yield goals, avoiding overuse.
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When soil tests indicate deficiencies, fertilizer with phosphorus, potassium and sulfur should be applied before planting.
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Water stress can be avoided by sufficient irrigation.
3. Root Rot: In India, root rot is caused by Rhizoctonia bataticola and Rhizoctonia solani. The pathogen mostly affects the lower part of the stem and roots. The disease symptoms include wilting of plant foliage from top to bottom.
Remedies
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Deep summer plowing should be applied and infected plant debris should be removed and burned.
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4 tons of farmyard manure per acre or 60 kg of neem cake per acre should be applied for the soil enrichment.
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Seeds should be treated with Bacillus subtilis (10g/kg) or Trichoderma asperellum @ 4 g/kg.
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Drench should be spotted with Carbendazim @ 1 g/l or Trifloxystrobin + Tebuconazole @ 0.75g/l at the base of affected plants and surrounding healthy plants.
4. Fusarium Wilt: Fusarium wilt is caused by the fungal pathogen Fusarium oxysporum, which is both seed and soilborne. It appears in any crop growth stage but is seen generally between 30 to 120 DAS. Symptoms include color change of the mainstem (especially the xylem), pathogen colonization, and growth in the plant vascular system.
Remedies
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Deep summer plowing should be applied and infected plant debris should be removed and burned.
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Seeds should be treated with Bacillus subtilis (10g/kg) or Trichoderma asperellum (4g/kg).
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During sowing and at 90 days after sowing (DAS), Trichoderma asperellum should be applied at a rate of 1 kg per acre.
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1 kg of T. asperellum should be mixed into 100 kg of farmyard manure and then it is allowed to multiply for 15 days before application.
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Drenching with Carbendazim 50%WP @1g/ lit of water should be done.
5. Alternaria Leaf Spot or Blight: Symptoms are seen on the leaves, bracts, branches and stems. The disease appears at the boll formation stages. Dark brown to black spots with concentric rings can be spotted on lower to upper leaves.
Remedies
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Infected plant residues should be destroyed and removed.
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Deep ploughing should be performed during summer.
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Seeds from infected crops should not be used.
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Copper oxychloride @ 500 g or Chlorothalonil @ 200 g or Difenaconazole @ 100 ml should be sprayed at the interval of 60, 90 and 120 days after sowing.
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Bacillus subtilis (BSC5) @ 400 g/ac should be applied on 60, 90 and 120 days after sowing.
6. Cercospora Leaf Spot: Cercospora leaf spot is caused by Cercospora gossypina. It usually affects the older leaves but may spread over the whole plant in favorable weather. Symptoms include circular or irregularly shaped spots that are dull and dark brown in color, with a gray center and dark brown to purple edges. These typically begin on the lower leaves and gradually spread to the upper leaves.
Remedies
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Infected plant residues are removed and destroyed..
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Mancozeb @ 400g/ acre or Copper oxychloride @ 500 g/ acre or Carbendazim 50% WP @ 200g/acre or Propiconazole @ 200 ml/ acre should be sprayed at the intimation of the disease.
7. Boll rots: “Boll rot” is a common term that is used to describe the rotting of cotton bolls due to insect-pest damage, several external, and internal pathogens and saprophytic organisms. External boll rot starts from lower to middle bolls and appears at boll formation stages (120-180 DAS) and internal boll rot can be observed when bolls are cross-sectioned or opened.
Remedies
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Optimum spacing should be adopted.
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Recommended doses of fertilizers should be applied.
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Copper oxychloride @1000 g/acre or Carbendazim @ 200 g /acre or Mancozeb @ 800 g / acre should be applied.
(Source -Central Institute for Cotton Research, Tamil Nadu Agriculture University)
