Cotton wilt

Symptoms are also known as half yellow, golden yellow, wilting disease. Cotton can be affected throughout the growing period and is a typical vascular disease. Symptoms often manifest themselves in multiple types: blue-yellow, yellow-yellow, yellow reticulate, wrinkled, red-leaf, etc.; budding, wrinkled, half-yellow, bleb-type, and apical-type. , light stalk and so on. The green and dry cotton strains were suddenly dehydrated after being infected by pathogens, and the leaves became soft and drooping and wilting, and then the cotton plants died of blue and dry. The yellowing type mostly occurs from the edges of the leaves, yellowing locally or in the whole leaves, and finally the leaves are dead or fall off, and the ducts and stems of the petioles become brown. The yellow reticulate cotyledon or true leaf veins turn green and yellow, and the mesophyll remains green. The diseased area shows reticular markings, gradually expands into plaques, and finally the whole leaf wilts or falls off. This type is one of the common symptoms of this disease. Shrinkage is characterized by leaf shrinkage, thickening, dark green leaves, shortened internodes, dwarfing plants, and sometimes with other symptoms. The red-leafed seedlings encountered low temperatures, some or all of the diseased leaves developed purplish red lesions, and the diseased leaves were also reddish-brown. The leaves shed with this withering and the cotton plants died. Half of the yellowing type cotton plants showed diseased yellowing withered in the half of the leaves and the other half grew normally. The disease sometimes occurs in combination with Verticillium wilt, and the symptoms are more complicated, with dwarf withering or withering. The longitudinal stem shows dark brown stripes in the xylem. When the humidity is high, the pinkish mildew appears in the diseased part, which is the pathogenic bacteria conidiophore and conidia.

The pathogen Fusarium oxysporum f. sp. vesinfectum (Atk.) Snyder et Hansen called Fusarium oxysporum wilt specialization, belonging to the semi-known fungus Subphylum fungi. The hyphae are transparent, separated, and conidia are produced on the lateral spores. Large conidiophores were sickle-shaped, slightly curved, slightly pointed at both ends, with 2-5 septa, mostly 3, size 22.8-38.42.6-4.1 (μm). There are three types of cultured spores of Fusarium solani in China: Type I spheroids or even sickles, with more than 3-4 septae, and obvious or indistinguishable footpods, which are typical tip spore types. Type II conidia are broad or short and slender, mostly 3-4 septa, with large morphological changes. The type III conidia are obviously short and wide, the top cells have blister or blunt, the spores are narrow and wide, and there are 3 septa. Small conidia are ovoid, colorless, mostly single cells, size 5-11.72.2-3.5 (μm). Chlamydospores are terminal or meristem, yellow, solitary or 2-3 consecutive, spherical to ovoid. Colonies of Fusarium oxysporum vary depending on the strain, physiological race, and culture medium. There are 6 foreign races of the pathogenic bacteria reported in China. In addition to the No. 3 race, the new races No. 7 and No. 8 of the new race in China, among which the race No. 7 is widely distributed in China, and the disease is strong, which is a small advantage. Species.

Transmission routes and conditions Fusarium oxysporum mainly overwinters in seeds, diseased bodies or soil and manure. The transportation of the seed with bacteria and the seed and fertilizer has become the main primary infestation source in the new ward, and the cultivation, watering and agricultural operations in the diseased cotton fields are the main approaches for close communication. In the case of field crops, debris from leaves and branches grow up under conditions of high humidity and spores spread by air or wind and rain, infecting the surrounding strains. The bacterium can survive for 5-8 months both inside and outside the seed. The diseased corpse survives for 0.5-3 years. When there is no residue, it can rot in the cotton field for 6-10 years. The conidia, chlamydospores, and microsclerotia of germs germinate under suitable conditions, producing hyphae, which invade from the wounds of the cotton roots or directly from the epidermis or root hairs of the roots, expand within the cotton plant, and enter the vascular tissue. Afterwards, conidia are produced in the catheter and extend upward to stems, branches, petioles, stalks and seeds of cotton bolls, resulting in discoloration of leaf or veins, tissue necrosis, and wilting of cotton plants. The occurrence of the disease is closely related to temperature and humidity. The temperature begins to appear at about 20°C, and the temperature rises to 25-28°C. When the ground temperature is higher than 33°C, the growth and development of the bacteria is inhibited or a temporary disability develops. When the ground temperature drops to around 25°C, the second peak will occur again. After the heavy rain or heavy rain in summer, the fall in the ground temperature is prone to disease. Poor terrain, soil viscosity, partial alkali, poor drainage or partial application, over-application of nitrogen fertilizer, or application of organic fertilizers that are not adequately decomposed with bacteria, or root-knot nematodes, have a higher incidence of cotton fields.

Control methods (1) Selection of resistant and resistant varieties. Disease resistant varieties include Shan 401, Shan 5245, Chuan 73-27, Lukang 1, No. 86-1, Jinmian No. 7, Yanmian No. 48, Shan No. 3583, Chuan 414, Xiangmian No. 10, and Sumian No. 1 No. 7, Qinmian No. 7, Liaomian No. 10, Lumian No. 11, Zhongmian No. 99, No. 6661, No 2031, No. 343, Jinmian No. 12, No. 21 and so on. Disease-resistant varieties include Liaomian No. 7, Jinmian No. 16, Zhongmian No. 18, and No. 252. In regions with mixed wilt and verticillium wilt, we advocate the selection of resistance to wilt disease, verticillium wilt, or resistant varieties such as Shan 1155, Liaomian 7, Yumian 4 and Zhongmian No. 12. (2) Implement a large area of ​​rotation. It is advisable to rotate with grass crops and promote rotation with rice. The effect of disease prevention is obvious. (3) Serious quarantine protection for the disease-free area. At present, China has no disease in about two-thirds of the cotton area, so we must do everything possible to protect the disease-free zone. Non-disease cotton species must not be drawn from the ward. Use of non-hot pressed cotton cake in the ward area is strictly forbidden to prevent the introduction of blight and Verticillium wilt. Promote the use of composted compost or decomposed organic fertilizers. (4) Eradicate the bacteria source in the soil to remove sporadic diseased plants. The diseased field with a disease rate of 0.1% or less is classified as a star disease field. When the diseased plant was found, the sick plants around the diseased plant were detected before the cotton growing period or after the cotton culm was collected after flowering, and the soil was disintegrated after the soil within 1 m of the diseased plant. Use 50% cotton wettable powder 140g or cotton wool powder 70g to mix well with loose soil, and then water 15-20L to make it infiltrate into soil and close tightly with dry fine soil; also use nitrogen 16 1% of agricultural ammonia water is applied to 9 parts of water, and 45L of liquid medicine is applied to every m2 of sick soil. After 10-15 days, the soil of watering liquid is dispersed to avoid residual poison or phytotoxicity. (5) Disinfection of cotton seeds and cotton cakes. The cotton seeds are soaked with sulfuric acid and 0.2% antibacterial agent 402 liquid is used, warmed to 55-60°C warm soaking for 30 minutes or 063% 50% carbendazim suspension is soaked at normal temperature for 14 hours, after drying sowing. When the cotton cake is used as a fertilizer, the cotton cake prepared by stir-frying the cottonseeds at 60° C. for 4 minutes or 100° C. steam for 1-1.5 minutes is sterile. (6) Transplant with seedling-free seedlings. (7) Continuously clean the cotton fields. In the past years, the litter and sick bodies in disease fields have been removed and burned on the spot, which can reduce the source of bacteria.