How to prevent and control cotton seedling diseases? Take multiple measures to ensure strong seedlings

Because rain kept falling continuously during the cotton sowing period and after emergence, this year's seedling death is more serious than in previous years, and the most severe cases have already begun to be destroyed and replanted.

1. Main symptoms

After cotton seedlings emerge, yellow-brown lesions appear at the base of the stem (where it meets the soil surface), gradually expand, become sunken and rotten, turn dark brown in color, and the cotton seedlings wither and die. This is typical "damping-off," commonly known by cotton farmers as "black neck" disease.

2. Causes of seedling death

1. Early sowing date and low temperature. According to forecasts from the meteorological department, the temperature in April 2008 was on average 3-5°C lower than in previous years, but most cotton farmers did not delay sowing according to the temperature, and some even sowed earlier, causing cotton to emerge slowly, prolonging the time for pathogen infection, and resulting in severe disease.

2. Excessive rain and high humidity. Within 15 days after cotton seedlings emerge, their resistance is weakest, and when they encounter low temperatures and high humidity, seedling diseases occur severely. This year, starting in late April, rain has been continuous, and cotton seedlings have been almost soaked in rainwater, so the roots cannot breathe. Excessive humidity caused a major outbreak of seedling disease, and cotton seedlings died in patches. Cotton fields in low-lying areas, with poor drainage, and with heavy clay soil had the most severe disease.

3. Severe continuous cropping. Because most cotton in our province is planted year after year, the number of pathogens in the soil has accumulated too much and the number of beneficial bacteria is too few, resulting in relatively severe seedling disease.

4. Poor quality of cotton seed coating agents. Many seed coating agents claim to resist insects and diseases, but after cotton seedlings emerge, they resist neither disease nor insects, and pests and diseases break out severely.

3. Control methods

1. Seed treatment. When replanting is needed, when crops are destroyed and replanted, or when sowing cotton after wheat or sowing summer cotton, because the current soil temperature is low and humidity is high, it is essential to do a good job of preventing seedling disease. Before sowing, mix 10 ml of Gaogiao and 50 g of Yiwei microbial agent with 1.5 kg of cotton seed to treat the seed or apply a second coating. This can effectively control continuous cropping diseases, make cotton seedlings sturdy, keep the incidence of seedling disease below 10%, and prevent aphids for 50-60 days.

2. Agricultural control. After the rain stops and the sky clears, measures should be taken to pull soil away from the cotton seedlings and expose the roots, reducing humidity around the roots, raising soil temperature, and alleviating disease occurrence. In areas with excessive rain, it is recommended to remove the plastic film after the sky clears to reduce humidity and protect the seedlings.

3. Chemical control. For cotton fields that have already developed disease or have severe disease, spray the root and stem area promptly. Effective agents include Ruimiaooqing 2000-fold solution + Yiwei microbial agent 500-fold solution, or Ruimiaooqing 2000-fold solution + Bihu 10000-fold solution, which can effectively control seedling death.

4. Control aphids in time. Choose agents with a long residual effect to control aphids, such as 600-fold Jinhaonian or 3000-6000 Le, which can achieve a residual effect of more than 20 days.