Cotton Wilt Disease and Prevention: A Technical Guide
Source: Seed Technology
Category: Technical Articles
Update Time: October 29, 2008, 16:20:29
Read: 69 times
Authors: Li Guorui, Zhang Gang, Cui Yingshu, Ren Yongxia (Kuantao County Bureau of Agriculture)
Cotton is a major economic crop that has seen increasing market value over the years, leading to an expansion in planting areas. However, the spread of yellow wilt disease has become a serious threat to sustained high yields and stable production. This article provides an overview of the symptoms, causes, and prevention strategies for cotton wilt diseases.
**1. Symptoms of Cotton Wilt**
Cotton yellowing disease is a vascular disease characterized by brown streaks on the stems. It can affect plants at various growth stages.
**1.1 Seedling Stage Symptoms**
At the seedling stage, there are five distinct types of symptoms:
- **Yellow Mesh Type**: Leaves appear green with yellow net-like patterns.
- **Yellow Type**: Leaves turn yellow, sometimes with small dead spots.
- **Purple Type**: Leaves take on a reddish-purple color, with purple veins and eventual wilting.
- **Blue and Dry Type**: Leaves suddenly lose water, turning dark green and appearing dry and blue.
- **Shrinkage Type**: True leaves thicken and shrink, becoming dark green.
**1.2 Adult Plant Symptoms**
In mature plants, symptoms include yellowing, purpling, and blue-dry conditions, as well as a dwarf type. Affected plants show shortened internodes, thickened and wrinkled leaves, and many severely affected plants have dried-out leaves.
**1.3 Verticillium Wilt Symptoms**
Verticillium wilt typically appears after the plant starts budding. The first signs are light yellow irregular patches between the leaf veins. Over time, these patches expand into brown, dry areas, while the main veins remain green, resembling a watermelon rind pattern. During hot and dry periods, acute wilting may occur, where leaves appear burned and fall off rapidly.
**2. Onset of Cotton Wilt Disease**
Fusarium wilt usually begins in mid-May and peaks around late June during the bud stage. The disease slows down as temperatures rise. A second peak occurs in late August. Verticillium wilt generally becomes active during the budding phase, with the highest incidence during flowering. Factors such as continuous cropping, poor drainage, and untreated seeds contribute to higher disease rates in old cotton fields.
**3. Control Measures for Verticillium Wilt**
**3.1 Select Resistant Varieties**
Modern varieties like Zhongzhimian 2 offer better resistance to wilt diseases.
**3.2 Agricultural Practices**
- **Crop Rotation**: Rotate crops for at least 3–4 years; severe cases require more than 7 years of rotation.
- **Balanced Fertilization**: Apply phosphorus, potassium, and micronutrients to strengthen plants and improve resistance.
- **Remove Diseased Plants**: At the seedling stage, remove infected roots and soil, and deeply bury them. For mature plants, pull out and burn diseased material to disinfect the soil.
**3.3 Chemical Control**
- **Seed Treatment**: Soak 100 kg of seeds in 200 L of water with 1 kg of 40% carbendazim suspension for 24 hours to control wilt and seedling diseases.
- **Fungicide Spraying**: Use fungicides like Greenhenge No. 1, 3, 4, 8, or high-resistance NEB (En Yibi) from American Science and Technology to prevent disease spread.
- **Fulvic Acid Fertilizers**: These help suppress wilting and promote healthier cotton growth.
By combining proper variety selection, good agricultural practices, and timely chemical interventions, farmers can significantly reduce the impact of cotton wilt diseases and ensure sustainable production.
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