The stem blight of cotton leaves is a physiological disease, and it is one of the major diseases in the middle and late cotton. At present, the growth of cotton in our country has entered the middle and late stages, and there are some stem blight diseases in some cotton fields. The disease usually begins in August. From September to late October to October, the onset of disease peaked. The lightly injured plants had small bolls, short fibers, poor boll opening, and the cotton bolls were not able to mature normally, which greatly affected the yield.
Symptoms In the early stages of disease development, the edges of the leaves are slightly yellow, and the mesophyll tissue is greenish. Some of the leaves turn purple or reddish brown and the veins remain green. With the development of the disease, the leaves were all reddish-brown or brown, and the edges curled downwards. The photosynthesis was greatly reduced. The nutrients produced could not meet the needs of cotton growth and development. The flower buds and juveniles lost a lot, the quality of the bells dropped, and the boll weight decreased. . Severe diseased leaves withered and littered into light poles, eventually causing the whole plant to die. The roots of the diseased plants were poorly developed, the main roots were short and fine, and the number of lateral roots was significantly reduced, with many turning dark brown. Most of the diseased leaves are mostly from bottom to top, developing from the outside to the inside, and some of the symptoms of diseased plants are turning red from top to bottom or turning yellow again and turning red. Cut open the stalk, and the vascular bundle does not change color to distinguish between dry and verticillium wilt.
The cause of the morbidity of the soil is that the soil is very thin, and the application of basal fertilizers and top-dressing is insufficient. In particular, the sites with little or no application of potassium fertilizer are heavy. High-yield fields with high bell-tightness, early-onset cotton fields, soils with drought, water after rain, saline-alkaline soil, shallow plough layers, many years of heavy cropping, cotton fields without mulching or uncovering the membranes are often not available due to nutrients or The poor development of cotton roots caused the growth of the underground and aboveground parts of the cotton plants and induced the occurrence of the disease.
Prevention and control methods for the prevention and treatment of cotton leaf blight, early prevention and early treatment should be done, the cotton fields that have already occurred should seize the time to prevent and control, it may happen as soon as possible.
1. Foliage fertilization with 50% potassium sulfate 100 times, or high-quality potassium dihydrogen phosphate 300 times plus urea 100 times mixed spray, spray every 10-15 days 1, even spray 3-4 times. Foliar fertilizer can also be combined with pest control at the same time to reduce labor.
2. Drought-fighting and watering Since the summer, rainfall in some areas has been less, and drought has been more serious. According to the characteristics of water requirement in the later growth period of cotton, it is still necessary to resist drought and water, ensure the water supply, adjust the fertilizer with water, and meet the requirements of cotton growth and development.
3 heavy rain drainage If precipitation is too large, we must promptly rule out the accumulation of water in the field to prevent internal hemorrhoids. Extend the growth time of cotton roots and promote nutrient absorption.
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