Thidiazuron is a new type of high-efficiency plant growth regulator with cytokinin activity. It can promote plant photosynthesis, increase crop yield, improve fruit quality, and increase fruit storage resistance. When used as a defoliant in cotton planting, after being absorbed by the plant, it can promote the natural formation of separation tissue between the petiole and the stem and fall off, making it a good defoliant.
Thidiazuron can promote the production of ethylene, inhibit the transport of auxin, and reduce the ratio of auxin to ethylene. 24 hours after the treatment of benzyl alcohol, the ethylene released by the leaves reaches a peak, and then maintains at a certain level until the leaves fall off. It can effectively remove both mature leaves and young leaves. It is currently the best harvesting aid for inhibiting secondary growth and removing young leaves, but the ripening effect is not as good as the defoliation effect.
Thidiazuron is slower to take effect than phosphate defoliants, especially at low temperatures, so it is not recommended to use it when the average daily temperature is below 21°C. Adding phosphate defoliants can increase the activity of thiazuron at low temperatures. Among all the harvesting adjuvants, thiadipyrone requires the longest rain-free time after spraying (24h), indicating that it is absorbed the slowest. Thidiazuron is also absorbed slowly in cotton subjected to drought stress. In this case, the dosage needs to be increased or adjuvants need to be added.
When the cotton bolls are cracked by about 70%, a solution with an active ingredient of 300~350mg/L is prepared and sprayed on the whole plant. The amount of solution used per mu is 30~40L. Leaves begin to fall on the 10th day, boll opening increases, reaching a peak on the 15th day, and decreasing on the 20th day. About 90% of cotton leaves can fall off, without harming the plants, and boll opening is normal. The efficacy of thiadipyrone is very obvious 5 days after use. The leaves still look green on the outside, but when the cotton leaves are touched lightly by hand, the leaves fall off from the base of the petiole, and the old leaves generally fall off faster than the young leaves. The peak of leaf shedding is 12~18 days after treatment, and the leaf shedding rate reaches more than 80% after 20 days. Benzodiazepine has a significant effect on the shedding of the lower leaves of cotton, which can improve the shade of the lower part of cotton in the late stage of cotton production, reduce cotton boll rot, increase the boll opening rate, and significantly increase the yield. When the natural boll opening rate of cotton reaches about 35%~40%, spraying the stems and leaves with thidiazuron 50%WP can effectively promote cotton defoliation, and also have a certain promoting effect on cotton boll opening, so that the proportion of flowers before frost is increased. Climate conditions (temperature, sunshine hours and humidity) have a certain effect on cotton defoliation rate and boll opening rate. High temperature and sufficient light before and after the application of the drug can promote the absorption of the drug, increase the defoliation rate and boll opening rate. It should be noted that: The application period should not be too early, otherwise it will affect the yield; Rainfall within 2 days after the application will affect the efficacy of the drug, and weather prevention should be paid attention to before the application; Do not pollute other crops to avoid drug damage.
