Multiple measures for comprehensive control of cotton diseases with symptoms

Symptom Identification of Cotton Fusarium Wilt and Verticillium Wilt

Fusarium wilt of cotton can occur in the whole growth and development period of cotton, but it occurs more seriously in the seedling stage, and it will also occur in the adult stage if favorable conditions are encountered. Ralstonia solanacearum type: the leaf suddenly loses water, the leaf droops and wilts, the leaf color is dark green, the leaf becomes soft and thin, the whole plant is green and dry and dies, but the leaf generally does not fall off and the petiole is curved. Yellowing type: it can occur at both seedling stage and adult stage. The yellowing type mostly occurs from the edge of the leaf, the local or whole leaf turns yellow, the leaf dies or falls off at last, and the vessel of petiole and stem turns brown. Purplish red type: mostly occurs in the seedling stage, the diseased leaves appear purple-red disease spots locally or entirely, the veins of the diseased leaves also show reddish brown, the leaves wilt and wither, and the cotton plants die. Shrinking type: it can occur at both seedling stage and adult stage, and the typical symptoms are leaf shrinkage, thickening, dark green leaf color, shortening of internodes, dwarfing of plants, and general non-death. Yellow reticulate pattern: mostly appeared in the seedling stage, the leaf veins of the diseased plants turned green, the mesophyll remained green, the leaves showed yellow reticulation in part or most of the leaves, and finally the whole leaves wilted or fell off. Half yellowing type: mostly occurred in the seedling stage, only half of the infected cotton plants showed yellowing wilt, the other half grew normally, when mixed with Verticillium wilt, the symptoms were dwarf wilt or wilt, and the xylem showed deep stripes in the longitudinal section of the diseased stem. Acute wilting type: most of them occur in the adult stage, sunny after heavy rain, acute wilting symptoms often appear in seriously diseased fields, cotton plants suddenly lose water, wilt, green wilt, droop, leaves, buds and flowers fall off to form light culms, and the top of the main stem and fruit branches are scorched.

Cotton Verticillium wilt can occur in the whole growth period, but there are few symptoms in the seedling stage under natural conditions. generally, about 40 days after sowing, the cotton plant bud stage begins to occur, and the disease in the middle and later stage is more serious than that in the early stage. Macular type: most of them show symptoms in the budding stage and develop slowly. The diseased plants begin to develop from the lower leaves and gradually develop upward. At the initial stage of the disease, the edges of the leaves curl upward, the flesh spitting between the veins produces light yellow irregular disease spots, and the veins remain green. Generally, the leaves do not die in the early stage and the leaves do not fall off. Leaf withered type: the leaf showed local withered spot or palm-shaped withered spot, and the leaf fell off after death, but the cotton plant generally did not form a light culm. Wilting type: it mostly occurs in the boll setting period, and there can be a kind of acute yellow wilt after heavy rain, which produces water-like light green plaques between the main veins of the leaves, and the leaves wilt and droop quickly. Deciduous type: the damaged plants generally showed the symptoms of the upper leaves first, and the typical symptoms were that the leaves wilted and drooped and fell off rapidly, and the cotton plant had formed a light culm before dying.

The difference between Fusarium wilt and Verticillium wilt of cotton Fusarium wilt causes leaf vein yellowing, verticillium wilt causes mesophyll yellowing; Fusarium wilt cotton plants are easy to fall leaves into light culms, Verticillium wilt cotton plants only appear sudden leaf wilting in a few years after prolonged drought and rainstorm or soaking in heavy water, and then fall off into light culms. The dwarf Internode of Fusarium wilt cotton plant type becomes shorter, and the cotton plant of Verticillium wilt is generally not dwarfed, but the cotton plants with earlier and more susceptible disease sometimes become dwarf, but the symptoms are generally not obvious; the vascular bundles with Fusarium wilt become dark brown after cutting, and those with Verticillium wilt are light brown.

Select varieties to highlight the word "resistance"

The selection of varieties with strong disease resistance can effectively control the degree of disease, which is the most important basic factor for disease control. In this regard, it is recommended that the vast number of cotton farmers look for varieties with strong disease resistance in the actual planting of cotton farmers around them, and do not believe the lies of "stooges" who only know "to sell more seeds for themselves." Only by selecting a variety with strong disease resistance recognized by the majority of cotton farmers in actual planting can we ensure that cotton has less disease and less medication.

The quality of cotton seed includes two aspects: one is the strength and weakness of the disease resistance of the variety itself, and the other is the good and bad of seed chemical treatment. In general, enterprises that produce excellent cotton seeds with strong disease resistance, in order to make their own cotton seeds "better and better", will use high-grade and high-efficiency seed coating agents such as Shileshi plus Apron or Weifu (Weifu Ling plus thiram) for seed coating treatment. this has a very good effect on effectively reducing the early disease of cotton and alleviating the disease in the later stage.

Field management highlights the word "strong"

In the field planting management, strengthening scientific planting management can not only effectively reduce the occurrence of cotton Fusarium wilt and Verticillium wilt, but also help to increase cotton production and efficiency.

Under the condition of rotation, rotation with Gramineae crops for more than 3 years should be carried out as far as possible, so as to effectively reduce the source of soil bacteria. Measures such as winter ploughing, deep ploughing and high ridge planting can be adopted as far as possible in the old cotton area without the condition of crop rotation.

In addition to drying seeds before sowing (early emergence and strong seedlings), appropriate late sowing (shortening seedling emergence and promoting strong seedlings), formula fertilization (especially paying attention to stabilizing phosphate fertilizer, increasing potassium fertilizer and adding micro-fertilizer, which can obviously reduce the incidence of disease), the practice in various places has proved that cotton seedling transplanting is also a measure to reduce the occurrence of diseases. Raising seedlings in a nutrient bowl of disease-free soil or transplanting seedlings without soil can effectively reduce the infection of pathogens in the seedling stage, postpone the disease, and significantly improve the disease resistance of cotton plants.

Cotton is a potassium-loving crop, the application of potassium fertilizer can significantly reduce the incidence of disease and help to increase production. However, in the case of soaring fertilizer prices this year, more cotton farmers have used compound fertilizer or compound fertilizer with less phosphorus and potassium. If the use of pure phosphorus and pure potassium is too little, it should be replenished in time in the full bud stage to strengthen cotton plants and enhance disease resistance.

During watering, 0.5 kg potassium permanganate per mu can be applied with watering, which can better inhibit the disease.

Chemical control highlights the word "prevention"

Compared with other varieties, the disease of cotton varieties with strong disease resistance is lighter under the same conditions, but it does not mean that "immortal seedlings" and "immortal trees" ("immortal seedlings" and "immortal trees" are often exaggerated propaganda for selling seeds. At present, no cotton species can achieve "immune" resistance), nor can it be controlled without pesticides.

According to the experience of cotton popularization and planting for many years, the author puts forward the idea of "one control and two promotion" in chemical control, and summarizes several formulations, which have achieved remarkable results in some cotton planting areas in Hebei, Shandong, Henan, Anhui, Hubei and Tianjin. Specific methods: fungicide (control disease) plus nutritional agent (promoting strong seedling) plus promotive regulator (promoting strong seedling).

The better fungicides are more than 80% carbendazim, Liugao brand allicin, 70% sodium sulfonate, 3% antimycin, Yizhiling, Yizhikang 3 (high purity allicin plus synergist), 36% cotton kujing (trichloroisocyanuric acid, should not be mixed with organophosphorus pesticides), 70% carbendazim, etc.

The better nutrients are high-quality potassium dihydrogen (need to beware of products impersonated by magnesium sulfate in the market), Hongfu diammonium solution, cotton disease resistance and high yield, boron, potassium, zinc, titanium fertilizer, potassium fulvic acid and so on.

The better promotive regulators are brucine neku, DA-6 (amine ester), compound sodium nitrate, Nongxi 10-potent and so on.

Usage: choose one of the above products in each category and mix them at the same time. Pay attention to the alternate use. Spraying prevention before each rain or watering, and spraying again after rain or watering can effectively control the spread of bacteria and significantly reduce the incidence of the disease. At the same time of spraying, the effect of root irrigation on seriously diseased plants and cotton plants within 1 meter radius was obviously better than that of simple spray.