Cotton Red Leaf Stem Blight and its Control measures

First, symptom recognition

After the disease, the leaves became dark green and thickened and brittle, and then scattered red dots on the leaves, and finally the whole leaves turned red, and the leaf veins remained green, which was called red leaf stem blight. When the disease is serious, the petiole base becomes soft, dehydration shrinks, causing the leaf to wither and fall off, and the top of the stem is dry-scorched. At the same time, it is easy to cause repeated infection of ring spot and brown spot, causing the diseased plant to scorch and die. Some plants can still sprout after falling off their diseased leaves. The plants with severe and early disease were short and small, the root system was poorly developed, and the main root and lateral root were short and thin.

Second, etiological analysis

The disease is a non-infectious disease, that is, a physiological disease of cotton, which is caused by a variety of abiotic factors. Environmental conditions such as fertilizer, water, soil, climate and farming system are closely related to the disease, especially drought and lack of nutrition.

1. The vegetative and reproductive growth of cotton is exuberant in the middle and later stage, and the demand for fertilizer and water is large. Once the fertilizer and water is insufficient in this period, it is easy to cause the disease.

two。 Long-term drought and high temperature, soil tillage layer lack of water, hinder the normal metabolism, resulting in physiological disorders, resulting in cotton plant "premature senility" and serious disease.

3. Plants in a state of low potassium content for a long time can easily cause the prevalence of this kind of disease; in addition, plants grow vigorously with excessive application of nitrogen fertilizer in cotton fields, glycosides accumulate in leaves, and some sugars are transformed into glucosides (anthocyanins, such as anthocyanins). Red leaf stem blight can also be caused by magnesium deficiency.

III. Conditions for onset of disease

1. Related to soil water content

In the early growth stage of cotton, there are many Rain Water, the aboveground part of cotton grows fast and the plant type is large, but the root system is shallow and the ability to absorb nutrients is poor, so it is susceptible to disease; from July to August, it is dry for a long time and can not be irrigated in time, which is easy to cause water shortage in the tillage layer and affect the root system to absorb nutrients. In the case of rainstorm and sudden sunny weather in the cotton field after a long drought, the transpiration of the plant increased sharply. Due to the excessive soil moisture, which affected the root absorption, the underground nutrients and water could not enter the plant, and the above-ground organic nutrients could not be formed, transported and distributed, resulting in serious physiological disorders of cotton plants.

two。 Related to the level of fertilization

In the cotton field with sufficient base fertilizer and topdressing, the plant growth is robust and the disease is mild; the disease in the cotton field without base fertilizer is more serious than that in the cotton field without topdressing flower and boll fertilizer; the disease is serious in successive years with single application of chemical fertilizer, especially in cotton fields with partial application of nitrogen fertilizer, no application of potassium fertilizer or less application of potassium fertilizer.

3. The relationship with the soil quality of cotton field

The disease is serious in sandy soil or poor soil with shallow tillage layer, because this kind of cotton field has poor ability of water and fertilizer conservation, weak growth potential and poor disease resistance.

4. The relationship between tillage and cultivation system

The disease is serious in cotton fields that are too deep and too shallow during farmland cultivation, because it is not conducive to root growth and absorption of water and fertilizer; long-term continuous cropping in the old cotton area leads to the decrease of soil fertility and the severity of the disease; in the later stage of early-maturing varieties, the supply of fertilizer and water is insufficient or not in time. It's easy to cause the disease.

IV. Prevention and control methods

1. intensive and meticulous farming

Leveling the land, turning over and improving the soil deeply, and combining the use of land with the cultivation of land to enhance the water and fertilizer conservation capacity of the soil. In arid areas, ploughing should be done frequently to reduce evaporation, promote cotton roots to root down and absorb water and nutrients from the soil, and improve drought resistance.

two。 Heavy application of base fertilizer and skillful topdressing

Farm manure is often used as base fertilizer, and where possible, green manure or wheat-cotton rotation can be planted to supplement the deficiency of organic fertilizer, so as to achieve the purpose of improving soil and improving soil fertility, and change the present situation of long-term single application of chemical fertilizer, so as not to destroy soil aggregate structure. reduce the ability of fertilizer and water conservation; according to the law of fertilizer demand in each growth period of cotton, apply topdressing skillfully. Generally light application of seedling fertilizer, appropriate application of bud fertilizer, heavy application of flower and boll fertilizer, supplementary application of top fertilizer; attention should be paid to the cooperation of nitrogen, phosphorus and potassium in the types of topdressing, among which potassium fertilizer is particularly important; in the late growth period of cotton fields with signs of premature senility, spraying Handilong, potassium dihydrogen phosphate and urea as early as possible for direct absorption and utilization of leaves, so that it can quickly exert fertilizer effect and have obvious effect of protecting leaves and increasing production.

3. Rational drainage and irrigation

The water requirement of cotton is different in different growth stages, and less in seedling stage and bud stage. However, there is a great demand for fertilizer and water in cotton flowering and boll stage, and it is often encountered unexpectedly in summer drought and high temperature season, so it is necessary to irrigate and fertilize in time to achieve the purpose of disease resistance and yield increase. Drainage should be done in time when it is rainy in autumn to prevent poor root absorption and growth caused by waterlogging.

4. Re-application of flower and boll fertilizer

Early maturing varieties or early sowing cotton field cotton seedlings develop early, there are many peaches in the early stage and are easy to encounter the dry season, so the phenomenon of "premature senility" often occurs, so it is necessary to apply and re-apply flower and boll fertilizer as early as possible to ensure the backward movement of fertilizer and water and ensure the steady growth of cotton. In order to reduce or avoid the occurrence of cotton red leaf stem blight.