The Incidence and Control of Cotton Verticillium Wilt
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Cotton Wilt Disease and Prevention: A Technical Guide
Source: Seed Technology
Category: Agricultural Research
Published: October 29, 2008, 16:20:29
Read: 59 times
Authors: Li Guorui, Zhang Gang, Cui Yingshu, Ren Yongxia (Kuantao County Bureau of Agriculture)
Cotton is a vital economic crop that has seen increasing profitability as market demand grows, leading to an expansion in planting areas. However, the rapid spread of cotton yellow wilt disease has become a major challenge for maintaining high and stable yields. This article explores the symptoms, causes, and effective prevention strategies for both Fusarium and Verticillium wilt diseases.
**1. Symptoms of Cotton Wilt**
Cotton yellow wilt is a vascular disease that affects the plant’s internal structure, causing brown streaks on the stems. The symptoms vary depending on the stage of growth and the type of wilt.
**1.1 Symptoms at the Seedling Stage**
During the early growth phase, five distinct types of symptoms may appear:
- **Yellow Mesh Type**: Leaves turn yellow with a net-like pattern while still retaining some green color.
- **Yellow Type**: Leaves show overall yellowing, sometimes with localized dead spots.
- **Purple Type**: Leaves develop reddish or purplish discoloration, with purple veins and eventual wilting.
- **Blue and Dry Type**: Leaves lose water rapidly, turning dark green and appearing dry and brittle.
- **Shrinkage Type**: True leaves thicken and shrink, appearing dark green and distorted.
**1.2 Symptoms in Mature Plants**
In adult plants, symptoms include yellowing, purpling, and blue-drying. In addition, a **dwarf type** may occur, characterized by shortened internodes, curled and thickened leaves, and uneven texture. Severely affected plants often have many dried and fallen leaves.
**1.3 Verticillium Wilt Symptoms**
Verticillium wilt typically does not affect seedlings but becomes evident after bud formation. Initially, the middle and lower leaves show irregular yellow patches between the veins. These patches gradually expand into brown, dry areas, while the main veins remain green, resembling a watermelon rind pattern. During periods of drought followed by heavy rain, an acute wilting form may occur, where leaves appear burned and fall off quickly.
**2. Onset and Spread of Cotton Wilt**
Fusarium wilt usually begins in mid-May and peaks during the budding stage in late June. As temperatures rise, the disease slows down, but a second peak may occur in late August. Verticillium wilt generally starts during the budding period and reaches its height during flowering. Factors such as continuous cropping, poor drainage, and untreated seeds contribute to higher infection rates, especially in old cotton-growing regions.
**3. Control Measures for Verticillium Wilt**
**3.1 Select Resistant Varieties**
Modern cotton varieties like Zhongzhimian 2 offer improved resistance to wilt diseases. Choosing disease-resistant strains is a key step in long-term management.
**3.2 Agricultural Practices**
- **Crop Rotation**: Rotate crops for 3–4 years; severe cases may require up to 7 years of fallow.
- **Balanced Fertilization**: Apply phosphorus, potassium, and micronutrients to strengthen plants and improve their resistance.
- **Remove Diseased Plants**: In early stages, remove infected roots and soil. After growth, pull out diseased plants and burn them to prevent spread.
**3.3 Chemical Control**
- **Seed Treatment**: Soak 100 kg of seeds in 200 liters of water with 1 kg of 40% carbendazim suspension for 24 hours to control wilt and seedling diseases.
- **Fungicide Spraying**: Use products like Greenhenge No. 1, 3, 4, 8, or NEB (En Yibi) to suppress disease spread and enhance plant immunity.
- **Fulvic Acid Fertilizers**: These fertilizers are highly effective in reducing wilting and improving plant health.
By combining these strategies, farmers can significantly reduce the impact of cotton wilt and ensure more sustainable production.