How to manage cotton in the mid-to-late stage? Hebei strengthens technical guidance

At present, spring-planted cotton in Hebei Province is successively entering the flowering and boll-setting stage from south to north. Due to a good sowing foundation, timely field management, abundant early rainfall, and sufficient sunlight, the cotton in Hebei Province has a neat plant type, steady growth, relatively light pest and disease damage, and field growth is generally better than in previous years. Recently, the provincial cotton expert advisory group conducted a field survey of cotton in 21 counties (cities) across 4 cities: Handan, Xingtai, Hengshui, and Cangzhou. According to the survey, the average plant height is 60-70 cm, the number of main stem leaves is 15-17, and the number of fruiting branches is 8-12. The growth and development process is basically normal, and a foundation for high yield has been established. The main problems currently existing are: first, due to excessive early rainfall and untimely chemical regulation, individual plots are growing too vigorously with relatively tall plant types; second, due to recent sustained high temperatures, aphids, red spider mites, plant bugs, and other pests have occurred relatively severely in some cotton fields, bringing adverse effects on cotton growth. Currently, it is the cotton flowering period and also a critical period for mid-to-late stage cotton management. All localities are required to adapt to this year's climate characteristics, seize favorable opportunities, adjust measures to local conditions, provide classified guidance, and effectively strengthen mid-to-late stage cotton management to strive for a bumper cotton harvest.

The cotton expert guidance opinions for mid-to-late stage management are:

I. Scientific fertilizer and water management

1. Timely watering. After flowering, cotton fields enter the peak water demand period. Watering should be done according to weather and actual field conditions when drought occurs. Especially under the recent sustained drought and high temperature weather, attention should be paid to timely watering, and there should be no mentality of waiting for rain. The watering indicator is that when the top leaves of cotton plants wilt at 4 p.m., watering can be carried out.

2. Heavily apply flowering and boll-setting fertilizer. The flowering and boll-setting stage is a key period for cotton fertilizer demand. Combined with irrigation or rainfall, timely topdressing should be carried out. Generally, 10 kg of urea is applied per mu. For cotton fields showing a trend of premature senescence, an appropriate amount of potassium fertilizer should also be applied. Specifically, it depends on cotton growth performance and should be flexibly controlled according to weather changes. For cotton fields with drought weather, less base fertilizer, poor soil fertility, and weaker cotton plant growth, flowering and boll-setting fertilizer should be applied early and heavily, so as to "apply at flowering and use for boll-setting." Deep application by trenching is recommended to improve fertilizer efficiency.

3. Spray foliar fertilizer to prevent premature senescence. In the late growth stage of cotton, a 60-fold urea solution or a 500-fold potassium dihydrogen phosphate solution can be sprayed on the leaves, with 70 kg of solution sprayed per mu each time, once every 7 days, for 2-3 consecutive times.

II. Timely chemical regulation and timely pruning

According to the principle of "small amounts and multiple applications, first regulate then promote, light first and heavy later," scientific chemical regulation and timely pruning should be carried out according to cotton growth and rainfall conditions.

1. Scientifically apply mepiquat chloride. Chemical regulation should be flexibly controlled according to cotton growth and weather conditions. It should not be used when the soil is short of water and cotton growth is inhibited. Before topdressing and watering or rainfall during the flowering and boll-setting stage, timely chemical regulation should be carried out. Generally, after initial flowering, 2-3 grams of mepiquat chloride per mu is used; for cotton fields with poorer growth, 1-2 grams per mu; for cotton fields with excessively vigorous growth, it can be increased to 3-4 grams per mu, diluted with 50 kg of water, and sprayed evenly. If rain occurs after spraying, re-spray in time. For cotton fields with good fertilizer and water conditions and vigorous growth, it can be sprayed 2-3 times, with each interval no less than 1 week.

2. Timely topping. According to the principle of "when the time comes, do not wait for branches; when branches come, do not wait for time," cotton fields with medium fertility are generally topped on July 15-20, and late-developing cotton fields can be postponed to around July 25. The time for removing side shoots of cotton is generally before August 10. For cotton fields retaining leaf branches, when the fruiting nodes on leaf branches reach 3, the top should be removed in time, or when flowers appear on the cotton plant, the top of the leaf branch should be removed. Empty plants and empty branches should be removed in time to improve ventilation and light conditions.

3. Use chemical ripening technology. For cotton fields that show excessive vegetative growth and late maturity in the later stage due to low temperature, continuous rain, and insufficient sunlight, ethephon can be sprayed to promote cotton boll maturity.

III. Integrated prevention and control of pests and diseases

The main types of pests and diseases in cotton fields in our province include cotton bollworm, aphids, cotton plant bugs, and verticillium wilt. Based on analysis of the current occurrence and control situation of cotton pests and diseases and meteorological conditions, cotton areas such as Handan, Xingtai, and Hengshui should mainly focus on the control of summer aphids, while the Cangzhou cotton area should focus on the control of cotton plant bugs. When implementing pest and disease control, all localities should pay attention to simultaneously controlling other pests, especially the control of older larvae of the third generation of cotton bollworm.

1. Cotton bollworm. When the number of larvae of the 3rd instar or older reaches 5 per 100 plants, chemical control should be carried out. Pyrethroid, organophosphorus pesticides, or compound formulations with contact or stomach toxicity should be selected, and the amount of pesticide solution per mu should not be less than 60 kg.

2. Plant bugs. Pesticide application should seize the peak hatching period of larvae. The specific period is about 2-3 days earlier than the peak hatching period of cotton bollworm. In the central and southern cotton areas, it is generally in mid-July. When the number of insects reaches 5-10 per 100 plants, control should be carried out. Systemic insecticides and insecticides with strong knockdown power should be used, such as 50-75 ml of 40% profenofos emulsifiable concentrate or 70 ml of 25% phoxim-cypermethrin emulsifiable concentrate per mu, diluted with 60 kg of water for spray control. Applying continuously 2-3 times at 5-7 day intervals can simultaneously control summer aphids and cotton bollworm.