Cotton Seed Dressing and Prevention of Cotton Aphid
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Cotton aphids are a major pest that commonly affects young cotton plants. They are found throughout the country and are among the most significant pests in cotton-growing regions. These pests cluster on the undersides of leaves and tender shoots, feeding on plant sap. This feeding damages the cells, causing leaf curling, stunted growth, and the secretion of honeydew, which promotes fungal infections and interferes with photosynthesis.
In northern cotton regions, cotton aphids can complete 10 to 20 generations per year. Their damage typically begins in April and May, targeting newly emerged seedlings before spreading throughout the fields. The peak damage period usually occurs between May and June, and the population declines after mid-June. However, during dry years, the infestation can last longer. Miao Miao appears at the end of June, while Fuxi emerges in late July and August, adapting well to high temperatures. Heavy rain significantly reduces aphid populations, making rainy seasons unfavorable for them. On sunny days, however, their numbers can increase rapidly—Fuxi can complete one generation every 4–5 days, while Miao Miao takes over 10 days. Field generations often overlap.
Cotton aphids thrive at temperatures between 17°C and 24°C with humidity below 70%. Early sowing of cotton seeds increases the risk of infestation. When cotton is intercropped with wheat, rapeseed, or broad beans, the occurrence of aphids tends to be later and less severe.
To manage cotton aphids effectively, two main methods are used: seed treatment and chemical control.
**1. Seed Treatment**
(1) Using imidacloprid-based treatments, such as 10% imidacloprid EC or WP (100g per 3–5kg of seeds), or Weiyuan Fudie (70% imidacloprid dispersible powder, 15g per 3–5kg of seeds). The solution should be evenly sprayed on the seeds and mixed thoroughly, then left to soak for more than 24 hours. The longer the soaking time, the better, as it allows for full absorption of the insecticide.
(2) Treated seeds result in fewer seedling pests, reducing the need for pesticide use during the early growth stage. This not only protects the seedlings but also prevents resistance development in aphids. Farmers who have used this method report earlier budding and healthier plants. For example, in Qiuqiu County, farmers noticed that treated cotton began budding about seven days earlier than untreated cotton. Dong Xinghua, a farmer from Jixi, said he didn’t need to spray any insecticides from April 27 to May 31 after using imidacloprid-treated seeds. He plans to use a seed mixer next year for even better results. In contrast, neighboring farmer Chen Fusheng had to spray four times in the same period, which was physically exhausting. Seed treatment not only saves money on pesticides but also reduces labor significantly, proving its importance and necessity in modern cotton farming.
**2. Chemical Control**
Farmers should monitor key thresholds for intervention. When the leaf rolling rate reaches 45% on 2-3 leaf stages, and there are about 4,500 aphids per 100 plants, action is needed. After the third leaf stage, if the leaf rolling rate rises to 50% and there are around 6,000 aphids per 100 plants, control measures must be taken. For the fumonium prevention index, an average of 680 aphids per plant in early July indicates serious damage. In late July, when there are about 200 aphids per plant, it’s time to take action. When these thresholds are met, the following insecticides can be applied: 5% acetamiprid EC diluted 2500–4000 times, 3% acetamiprid ME diluted 1000–1500 times, 20% acetamiprid soluble liquid diluted 6000–8000 times, 25% imidacloprid WP diluted 6000 times, or 30% acephate EC diluted 1000–2000 times. Spraying should be thorough and precise to ensure maximum effectiveness.