Key Technical Points for the Use of Different Chemical Control Agents on Cotton

Chemical control of cotton means using chemical regulation methods to shape cotton into an ideal plant type and create a high-photosynthetic-efficiency population. In this way, plants can grow vigorously, pest and disease occurrence can be reduced, cotton yield can be increased, and quality can also be improved. However, there are currently many chemical control agents, and correct application techniques should be adopted according to different agents to achieve better results.

1. Mepiquat chloride. At present, mepiquat chloride is widely used in cotton chemical control, and its effect is also relatively ideal. It can reduce cotton plant height, decrease the number of fruiting branches, promote the shift of photosynthesis toward reproductive growth, reduce cotton boll shedding, increase the number of set bolls, and coordinate the contradiction between individual development and population development. Mepiquat chloride is applied 4 times during the entire cotton life. The first application is at the bud stage, using 0.51 g per mu diluted in 20 kg of water, which helps control the top and promote the bottom, stabilize growth and increase buds. The second is at the early flowering stage, using 1.51 g per mu diluted in 30 kg of water, which can prevent excessive growth and increase bolls. The third is at the flowering and boll stage, using 34 g per mu diluted in 30 kg of water, focusing on spraying the plant canopy and the top of fruiting nodes, so as to help shape a good plant type. The fourth is at the late stage. If there is a "running high" phenomenon, heavy control can be used, with 34 g per mu for topping, so as to help control late buds, shorten the upper fruiting nodes, and prevent the increase of ineffective fruiting nodes and the clustering of superfluous buds.

2. Mepiquat chloride. At the full bud stage and early flowering stage, use 5 mL of 25% mepiquat chloride per mu diluted in 40 kg of water, and at the full flowering stage use 10 mL for one spraying each time. This can effectively control excessive vegetative growth of cotton and reduce bud and boll shedding and the occurrence of boll-stage diseases.

3. Chitin. It can be used throughout the entire growth period of cotton. Spraying on the leaves with a 600-800 times dilution can enhance the stress resistance and disease resistance of cotton, and especially has a good preventive effect on cotton seedling diseases, Verticillium wilt, and Fusarium wilt.

4. Triacontanol. Soaking seeds with 0.1 mg/kg triacontanol for 8 hours can improve seed germination vigor and germination rate. Spraying 0.1 mg/kg triacontanol solution at the full flowering stage and the end of the full flowering stage can reduce bud and boll shedding.

5. Ethephon. Ethephon is mainly used in various late-maturing cotton fields and cotton fields that need to be cleared early. It is not suitable for cotton fields that can open bolls normally and have very low yield levels. Spraying should be chosen when the temperature will be higher than 20 degrees for several days after application. Only temperatures above 20 degrees can decompose and release ethylene and take effect, and it should be carried out when the boll period of the upper cotton bolls is more than 40 days. In northern cotton regions, spraying about 20 days before the arrival of the frost period is appropriate. Generally, use 40% ethephon aqueous solution at 300-800 times dilution, 60 kg per mu. When using ethephon for ripening, special attention must be paid to ensuring the spray liquid directly adheres to the boll body, minimizing interception by leaves. It must not be mixed with alkaline pesticides. Adding 0.2% neutral laundry powder as a wetting agent gives a better effect. It must not be used in seed fields.