Comprehensive Prevention Measures of Cotton Red Leaf Stem Blight

Cotton red leaf stem blight is a physiological disease. In recent years, cotton red leaf stem blight occurred in a large amount in the cotton area of the Yangtze River valley, and began to occur in the early flowering stage. the disease was more serious and common from full flowering stage to boll setting stage, and sporadic in July and August in our area. The disease reached the peak from mid-September to October, the light injured plants had few yellow thin bolls, short fiber and poor boll opening, while those with severe disease died ahead of time, and the cotton bolls could not mature, which had a great impact on the yield.

First, symptoms of the disease. In the early stage of the disease, the leaves appeared red and purple spots, which gradually expanded to the whole leaf reddish brown and brown, and the leaves fell off into smooth rods from bottom to top, and sometimes the diseased leaves could be red and yellow, accompanied by plant wilting, resulting in the death of the whole plant. The symptoms of wilting are particularly obvious when it first clears up after rain, which looks like cotton wilt from afar, but the vessel inside its stem and root does not turn black.

Second, etiology. Through years of investigation, it was proved that the occurrence of red leaf stem blight of cotton was more serious in the fields with insect-resistant cotton and less potassium application, and the occurrence of sandy loam soil was more serious than that of Magan soil. For example, in 2000, Red Leaf Stem Blight occurred in 150 mu of cotton in No. 1-4 of No. 8 Squadron of Menghu Farm, and all the leaves were lost on October 18, which had a great impact on the yield. According to the investigation, the four fields are all sandy loam, the cotton variety is insect-resistant cotton 410, the flower and boll fertilizer is not applied potash fertilizer and phosphate fertilizer, only cake fertilizer and urea are applied, and the amount of urea per mu is 40 kg and 25 kg respectively, which is 58.3% higher than that of the adjacent Menghu Seven Squadron.

In addition, the incidence of premature senescence is more serious, which is mainly due to the lack of fertilizer and water supply in the vigorous reproductive growth period, resulting in poor root growth environment, poor stress resistance of cotton plants and aggravating the incidence of red leaf stem and leaf disease. premature senile cotton plants are also easy to be infected by other bacteria and induce other diseases.

III. Prevention and control measures

1. Disease-resistant varieties were selected. Since the cotton bollworm occurred in the cotton area of the Yangtze River valley from 1998 to 1999, the pest disaster caused heavy losses to cotton farmers, and the planting area of insect-resistant cotton has reached more than 98%, which is one of the main reasons for the occurrence of cotton red leaf stem blight in our land. It is suggested that cotton varieties should be selected reasonably and hybrid cotton should be planted in an appropriate amount to inhibit the occurrence of cotton red leaf stem blight.

2. Fertilize reasonably and strengthen the management of fertilizer and water. To increase the application rate of organic fertilizer, topdressing should be applied step by step, the first light and then heavy, the reasonable proportion of nitrogen, phosphorus and potassium fertilizer, and appropriately increase the use of potassium fertilizer in potassium deficient fields. Do a good job in drought and drainage, timely irrigation and drought relief, coordinate the supply of fertilizer and water, and promote fertilizer with water.

3. Strengthen the field management. Timely mid-ploughing and dry season can cut off capillarity, reduce water evaporation, preserve soil moisture and promote the development of roots, which is beneficial to the growth of cotton plants and increase resistance. The diseased fields should be supplemented with available potassium fertilizer in time to reduce the occurrence of the disease.

4. Chemical control should be carried out in time. After the incidence of cotton, timely spray metalaxyl, carbendazim and other fungicides 2-3 times to prevent the invasion of other bacteria and alleviate the disease. When spraying, 100 grams of potassium dihydrogen phosphate can be used as foliar fertilizer, which can not only supplement fertilizer, but also achieve the effect of disease control.

Once cotton red leaf stem blight occurs, effective measures should be taken immediately to control the spread of the disease and reduce the loss.