Limiting factors and Countermeasures of Cotton production (part two)

7. The phenomenon of premature senescence is mainly manifested as follows: firstly, after the peak boll setting period of cotton, the leaves lose green and chlorosis among the veins, the chlorosis leaves develop from top to bottom and from outside to inside from the farthest distance from the main stem, and the leaves gradually dry and fall off. Second, cotton late growth, leaves turn red, lose the function of manufacturing nutrients. The earlier the premature senescence of cotton appeared, the more serious the yield reduction.

Causes: First, poor soil, soil fertility is insufficient. Soil nutrients can not meet the requirements of cotton growth and development; second, insufficient fertilization. Especially when potassium fertilizer and nitrogen fertilizer are insufficient, some cotton farmers are afraid that when the amount of nitrogen fertilizer is large, it will cause cotton to grow vigorously; Third, the cotton field is dry or waterlogged, resulting in poor growth; Fourth, the excessive growth of cotton field, caused by imbalance of nutritional growth and reproductive growth; Fifth, the plastic film cotton develops early, the root system senescence is also early, and the plastic film is not removed during the growth period, resulting in poor root development; Sixth, the high-yield field has many bolls, and the nutrients cannot meet the requirements of cotton growth and development.

Countermeasures: First, rational fertilization. K fertilizer should be applied as basal fertilizer or early topdressing fertilizer, and N fertilizer should be applied steadily, heavily for flower and boll, and topdressing fertilizer for cover. The second is watering in case of drought. When watering, it should be controlled to separate the ditch with small water to prevent excessive growth caused by rain after watering. Third, after the mulched cotton enters the rainy season, the mulched film shall be removed in time to prevent drought under the mulched film and affect the development of cotton roots. Fourth, timely drainage in case of waterlogging.

8. Late chemical control: when precipitation is too much or fertilizer and water are too much, cotton plants are tall, closed in the field, ventilation and light transmission are poor, and the middle and lower buds and bolls are seriously dropped, resulting in yield decline and quality reduction.

Cause: Cotton farmers do not master the technology of fertilizer and water management and chemical control well, and chemical control is carried out after cotton grows vigorously or even grows excessively.

Countermeasures: First, early chemical control of cotton fields with prosperous growth trend, do not wait until after prosperous growth. Second, after topdressing, watering and rainfall, timely chemical control according to fertilizer and water conditions. Third, chemical control should start from seedling stage to keep cotton plant growing steadily. The dosage of auxiliary nutrient is generally 1~ 2ml per mu at seedling stage, 6~ 12ml from full bud to early flowering stage, and 12~ 15ml at full flower and boll stage. Fourth, the chemical control concentration is better to be low than high. If the chemical control is still prosperous, it can be controlled once after 7~8 days, and the chemical control in the whole process is 3~4 times. Fifthly, timely watering in case of drought after chemical control.

9. Fusarium wilt and verticillium wilt are mainly manifested as follows: dwarfing of cotton plants, yellowing of leaves, occurrence of various symptoms such as patches, reticulation, blight and deciduous leaves, browning of vascular tubes of longitudinal cotton stems, few bolls, and death of whole plants in severe cases. Fusarium wilt and Verticillium wilt have a long onset time. Fusarium wilt starts from seedling stage, Verticillium wilt starts from bud stage, and the disease period lasts more than three months. These two diseases have a great impact on cotton yield.

Countermeasures: Fusarium wilt, Verticillium wilt in the soil survival time is long, there is no specific control method, control disease development measures cotton farmers do not master well. First, select disease-resistant varieties. The second is to cultivate strong seedlings and improve the disease resistance of cotton. The third is the two peak periods of Fusarium wilt and Verticillium wilt, that is, the budding period in the middle and late June and the flowering and boll period in August. The drug is applied once every 7~10 days for 3~4 consecutive times. Fourthly, a peak of disease is formed after rainfall or watering, and timely medication is applied after rainfall or watering. Fifth, 50% carbendazim wettable powder 1000 times or 70% thiophanate-methyl 800 times plus humic acid foliar fertilizer mixed spraying to control the development of diseases.

10. The main harm of blind stink bug is as follows: the young bud is damaged at the cotyledon stage, showing that the top is withered to form "male cotton"; the leaf is damaged to form "broken leaf madness"; the young bud is damaged from yellow to black, and falls off after 2 to 3 days; the medium bud is damaged to form a mouth bud; the young boll is damaged to produce water-stained spots, and the heavy ones are rigid and fall off; the top center or the side center is damaged to form "broom cotton".

Cause: First, with the promotion and application of insect-resistant cotton, pesticide dosage is greatly reduced, blind stink bug rises from secondary pest to main pest, and insect body is small, more activity harm after evening, not easy to be discovered by people. Second, due to the migration habits of blind bugs, the control effect of one household alone is very poor.

Countermeasures: First, according to the symptoms of cotton victims to take unified control in a timely manner as well. Second, the time of application should be around evening, and it is better to control the surrounding cotton fields in a unified way by taking villages as units, and it is better to control them in a unified way by counties and townships. Thirdly, acephate and pyrethroid pesticides can be selected as pesticides, or Lesben and pyrethroid pesticides can be used for control. Fourth, when spraying, pay attention to spraying evenly and thoroughly, and it is better to evenly apply the medicine to the front and back of the leaves.