Cotton disease control: grasp the key at the seedling stage

The main cotton seedling diseases include damping-off, anthracnose, black spot, seedling blight, and root rot. The main cause of cotton seedling disease is seed-borne and soil-borne pathogens; once suitable climatic and environmental conditions for disease development occur, cotton seedling diseases will break out severely, harming the normal growth of cotton seedlings, with the disease incidence in ordinary years being 30%-50%. In recent years, with the promotion of transgenic insect-resistant cotton, cotton seedling diseases have shown a trend of gradually worsening, directly threatening full stands from a single sowing and the early development of strong seedlings. Therefore, integrated control of cotton seedling diseases has become a safeguard measure that cannot be ignored for increasing cotton yields.

I. Strict seed disinfection. Vigorously promote the purchase and use of good-quality coated seeds to eliminate seed-borne pathogens and improve the effectiveness of disease and pest control. For any cotton field where coated seeds are not used, the cotton seeds used must also be treated with high-efficiency fungicides through seed dressing, seed smothering, or seed soaking, so as to carry out seed disinfection properly and prevent infection from seed-borne pathogens.

II. Timely sowing. Transgenic insect-resistant varieties have poor tolerance to low temperatures, emerge slowly, and have weak seedling vigor; sowing too early results in a long emergence period, high nutrient consumption, more opportunities for seedling disease infection, and severe disease. Therefore, sowing must not be too early or too late, and the principle of timely sowing must be followed. For ordinary cotton fields, it is advisable to sow when the soil temperature at 4 cm stabilizes at 14°C; for alkaline cotton fields, it is advisable to sow when the soil temperature at 5 cm stabilizes at 15°C-16°C.

III. Strengthen field management during the cotton seedling stage. In dry weather, for cotton fields with poor soil moisture, the seedling release holes should be sealed promptly as seedlings are released, so as to preserve moisture through the seeds; when soil moisture under the film is high and rainy days occur, the sealing of seedling release holes can be appropriately delayed, and the holes should be sealed only after the soil under the film becomes loose and the soil temperature is suitable, so as to facilitate moisture dissipation and reduce disease; for open-field cotton, soil should be loosened in time to keep warmth, moisture should be preserved in drought, moisture should be dissipated in waterlogging, and soil should be loosened near the seedlings; at the same time, timely thinning and final singling must be carried out, thinning after full emergence and final singling at one time when 1-2 true leaves have grown, so as to benefit the individual development of cotton seedlings and enhance disease resistance.

IV. Chemical control and nutritional strengthening of seedlings. After final singling, spray cotton seedlings with a mixture of fungicide and high-efficiency foliar fertilizer, which both prevents disease and strengthens seedlings, hitting two birds with one stone. When cotton seedling disease first appears, spray "Kejun" or carbendazim or thiophanate-methyl, plus 0.2% potassium dihydrogen phosphate or Duode rare earth pure nutrient agent. At the peak of disease occurrence, spray 2500-fold ethephon? No, 2500-fold "Eduling" plus 3500-fold Tianfengsu; for plots with severe cotton seedling disease, 1000-fold "Junjue" can be used alone for spray irrigation of cotton seedlings. During the cotton seedling stage, control is generally applied once every 7-10 days, for 2-3 consecutive applications, which can both reduce damage and losses and basically ensure the normal growth of cotton seedlings.