A Detailed Guide to the Application Methods of Several Chemical Regulators for Cotton

In cotton production, the commonly used chemical regulators include mepiquat chloride, chlormequat, ethephon, triacontanol, chitin, and others. Some of these chemical regulators can shape an ideal plant architecture, forming a high-photosynthetic-efficiency population per unit area; some can promote robust plant growth and reduce the occurrence of pests and diseases; and some have a ripening effect, effectively regulating the maturity period and thereby reducing the harm from disastrous weather. In short, scientifically applying various chemical regulators well in cotton production is beneficial for increasing yield and improving quality.

1. Mepiquat chloride can not only reduce cotton plant height, decrease the number of fruiting branches and boll shedding, and increase the number of set bolls, but also effectively coordinate the contradiction between individual development and population development, improve photosynthetic efficiency, and promote high yield. Generally, it can be applied 4 times during the cotton growing period. The first application is at the bud stage, spraying 0.51 g per 667 sq m mixed with 20 kg of water, to control upward growth and promote downward growth, stabilize growth and increase buds. The second is at the early flowering stage, spraying 1.51 g per 667 sq m mixed with 30 kg of water, to prevent excessive growth and increase boll setting. The third is at the flowering and boll stage, spraying 34 g per 667 sq m mixed with 30 kg of water, focusing on the plant canopy and the top of fruiting nodes, to regulate plant architecture growth. The fourth is before entering the boll-opening stage; if there is a tendency toward excessive growth, heavy regulation can be applied, using 34 g per 667 sq m mixed with 30 kg of water to top the plants, in order to control late buds, shorten the upper fruiting nodes, and prevent the proliferation of ineffective fruiting nodes and the clustering of redundant buds.

2. Chlormequat can not only repel insects, resist insects, and drive away insects, but also control excessive vegetative growth of cotton, making individual cotton plants grow compactly and robustly, enhancing the plant's physiological resistance, and reducing bud and boll shedding. To improve the spraying effect of chlormequat, application should be based on soil and seedling conditions. Generally, "third-grade seedlings" on poor soil, with insufficient water sources, and poor growth should not be treated. For fields with good fertilizer and water conditions showing excessive growth, 5 mL of 25% chlormequat per 667 sq m mixed with 40 kg of water can be sprayed once each at the full bud stage and early flowering stage. At the full flowering stage, 10 mL of 25% chlormequat per 667 sq m mixed with 40 kg of water can be sprayed once more.

3. Ethephon is mainly used in various late-maturing cotton fields and cotton fields that need ripening and early clearing of stubble. Spraying should be carried out when the temperature is above 20°C, which is favorable for the decomposition and release of ethylene. Application time and method: it is suitable to spray after the boll period of the upper cotton bolls reaches more than 40 days. In northern cotton regions, it is suitable to spray about 20 days before the arrival of the killing frost. Generally, 60 kg of a 300-800 times dilution of 40% ethephon aqueous solution per 667 sq m is sprayed. Note that when using ethephon for ripening, the solution should directly adhere to the boll body, minimizing interception by leaves; it must not be mixed with alkaline pesticides; and it should not be used on cotton fields that can open bolls normally, on low-productivity cotton fields, or on seed fields.

4. Triacontanol: When used before sowing, triacontanol can improve seed germination vigor and germination rate; when used at the full flowering stage and the end of the full flowering stage, it can reduce bud and boll shedding. The method is: before sowing, soak seeds with 0.1 mg/kg triacontanol for 8 hours; at the full flowering stage and the end of the full flowering stage, spray once each with 0.1 mg/kg triacontanol solution. When spraying triacontanol on cotton, it can also be mixed with pesticides (such as dimethoate, etc.) to control wheat aphids. For cotton with insufficient growth vigor in the middle and late stages, it can be mixed with quick-acting fertilizers (such as urea, potassium dihydrogen phosphate, etc.) for spraying.

5. Chitin can be used throughout the entire growth period of cotton. Application in the early stage can make the root system well developed, the stems and plants robust, and the leaves thick and large, and can also relieve the adverse effects of pesticide damage, fertilizer damage, and disastrous weather, enhance cotton's stress resistance, and promote balanced growth of cotton. It has a significant control effect on cotton damping-off, rhizoctonia rot, anthracnose, and especially on soil-borne diseases such as verticillium wilt and fusarium wilt. When applied in the middle and late stages, cotton buds are plump, boll shedding is reduced, cotton bolls expand quickly, and cotton quality is good. The application method is: for seed dressing, use a 50-100 times dilution, soak seeds for 12-20 hours, dry slightly, and then sow; when seedlings are 10-20 cm tall and at the bud stage, apply a 600 times dilution as a root drench once each; in the middle and late stages, spray 1-2 times with a 600-800 times dilution.