Cotton angular spot

Symptoms The disease not only damages the cotton seedlings, but also damages the stems and leaves of the adult plants and the developing bolls. The damaged cotyledons at the seedling stage suffer from water-stained irregular or round lesions, dark brown, and severe cotyledons withering off. The leaves of the diseased leaves firstly produce dark green dots and then expand into oil-like shapes. The leaves are positively spotted and polygonal. Sometimes the lesions spread irregularly along the veins, causing the leaves to fall off. The stem lesions are the main lesions in the current water situation. After the expansion of black or rot, the disease department sunken, the bacteria bent to one side. The top bud became infected and formed a "rotten top", resulting in the death of the whole plant. When the humidity is high, the diseased department secretes a thick yellow bacterial pus, which becomes dry under dry conditions. Film or broken into powder. Cotton stained with primary oil, dark green spots, later expanded into a nearly round or multiple lesions fused into an irregular shape, brown to reddish-brown, the Ministry of depression, young bell off, into Bell part of the heart rot. Pathogen Xanthomonas campestris pv. Malvacearum (EFSmith) Dowson said the Xanthomonas campestris var. mairei disease species (Xanthomonas oryzae) is a bacterium, rod-shaped bacteria, size 1.2-2.40.4-0.6 (( Μm), 1-2 flagellum on one end, can swim, have decidua. Gram-negative staining. Form light yellow circular colonies on PDA medium. 2-3 cell lines often become chains. The growth of the bacteria is suitable for 曙25-30), the highest temperature is 36-38°C, and the lowest is 10,50-51°C. It is lethal for 10 minutes. However, it can withstand 80°C high temperature and -21°C low temperature under dry conditions. In the process of differentiation, 18 physiological races have been identified. Transmission routes and pathogenic conditions Pathogenic bacteria are mainly wintered on seeds and soil diseased bells and other diseased bodies. Late spring cotton is sown by rain splashing and insects to carry out the spread and spread. The bacteria are sent to the main table after raining on cotton bolls. The water film invades from the pores or cracks in the epidermis and insect infestations, propagates in the intercellular space, destroys the tissues in the leaves, and produces symptoms after 8-10 days. The pathogens often invade into the vascular bundles through the diseased tissue, and then reach the seeds, causing seeds. The bacteria on the shells fell into the soil along with the diseased body and became the source of infestation at the beginning of the year. The disease is mainly transmitted by seeds, and the seed carrier rate is 6% to 24%. It survives within the seed for 1-2 years. The cotton area in the river basin occurs from June to September, and from July to August into the peak period. The relative humidity is higher than 85%. The number of rainfalls is large, and the amount of rainfall is large and susceptible to disease. In the event of a typhoon, the incidence is heavy. Island cotton susceptible Disease prevention and control methods (1) After the picking is completed, the residues of the diseased cotton field should be promptly removed, and the manure should be concentrated or burned. (2) Selection of cotton seeds, proper close planting, timely drainage after rain, prevention of moisture retention, and timely removal of diseased plants in combination with seedlings and seedlings. (3) The use of formula fertilization technology, promote the application of enzyme composting composting, avoid partial application, over-application of nitrogen fertilizer. (4) Promote the use of ridge cultivation or sorghum, scientific irrigation, and prohibit flood irrigation, string irrigation, and timely cultivating. (5) Seed treatment. Concentrated sulphuric acid is used for degreasing to eradicate cottonseeds. The specific method is shown in Verticillium wilt in cotton. It can also be soaked in warm water (55-60°C) for three and a half hours. (6) Selection of disease-resistant varieties. The cotton wool system in upland cotton has strong resistance, and Chinese cotton is also more resistant to disease. (7) Strengthen field management, apply fertilizer in time after typhoon and heavy rain, and spray 1:1: 120_200 times Bordeaux mixture or 25% Yezizole wettable powder 500 times solution or 72% agricultural streptomycin sulfate 4000 times solution .

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