What are the key field management points for cotton during the flowering and boll-setting stage?
The flowering and boll-setting stage of cotton is the key period for yield formation. In addition to good fertilizer and water management, the following points should also be done well:
Chemical regulation
Carrying out chemical control during the flowering and boll-setting stage can shift more nutrients from vegetative growth to reproductive growth and reduce the shedding of squares and bolls.
It is recommended that for cotton fields with strong growth, at the beginning of flowering, spray 2.0-2.5 grams of mepiquat chloride per mu, or 8-10 milliliters of 25% chlormequat. At full flowering, carry out chemical control once more according to growth, spraying 2.5-3.0 grams of mepiquat chloride per mu, or 10-12 milliliters of 25% chlormequat. The final chemical control should be carried out 7-10 days after the cotton tops are removed, when three fruiting nodes have appeared on the top fruiting branches, spraying 3.5-4.0 grams of mepiquat chloride per mu, or 14-16 milliliters of 25% chlormequat, focusing the spray on the side tips of the fruiting branches, with 40-50 kilograms of solution sprayed per mu. This is used to seal the group tips, cut off ineffective flower buds, and achieve the control effect of locking all four gates.
Timely topping
The suitable topping time should be determined according to the cotton yield structure, combined with density, the number of fruiting branches per plant, and the growth condition at that time.
Under conventional density, each plant should retain 13-15 fruiting branches, and topping should be done around July 15. For cotton fields with strong growth and low density, topping should be appropriately postponed to around July 20, but not later than the 25th, so that each cotton plant has an average of 17-18 fruiting branches, in order to fully utilize soil fertility and the high-yield advantage of the variety. For wheat-intercropped cotton and cotton fields with high density or poor soil, the topping time should be advanced to finishing topping from July 10 to 13; otherwise, yield and quality will be affected. Topping should adopt the method of removing the small top with one heart and one leaf to prevent the phenomenon of pulling off large handfuls.
Disease and pest control
The main diseases appearing during the flowering and boll-setting stage include yellow wilt and Fusarium wilt, red-leaf stem blight, as well as cotton boll blight, black boll disease, red rot, and pink rot. Starting in early August, fungicides should be sprayed on cotton plants, using 50% carbendazim, 50% thiram, or 65% zineb at 400-500 times dilution alternately, spraying 40-50 kilograms of solution per mu, once every 7-8 days, until the end of August. For plants already affected by yellow wilt and Fusarium wilt, root irrigation should also be combined, using 300 times dilution of Junjue, pouring 200-250 milliliters of solution per plant, once every 7-8 days, for 2-3 rounds. The main pests during the flowering and boll-setting stage include cotton bollworm, summer aphids, mirids, and red spider mites, which cause relatively serious damage and pose a great threat to yield, so timely control is required.
When controlling, adjust the strategy well, distinguish the primary and secondary targets of control, scientifically select pesticides, and apply pesticides promptly according to the damage characteristics and activity patterns of the pests, applying them accurately and effectively.