Early blight is the main disease of celery, which can occur severely in both open and protected areas. The pathogen infects the celery leaf and petiole, causing disease spots, causing the leaves or whole plants to be yellow, causing severe reduction in production and quality. It is necessary to timely carry out pesticide control.
[Symptoms] The diseased leaves have near-circular or irregular lesions with a diameter of 5 to 10 mm, taupe, dark brown edges, and a clear boundary with the surrounding healthy parts. Under humid conditions, gray-white mildew, which is the conidiophore and conidia of the pathogen, is produced on the lesion. Two or more lesions can meet each other, and the diseased leaves turn yellow and withered. The diseased spots on the petiole and flower stalks are initially elliptical, long fusiform, light brown, slightly sunken, and later developed into long strips of dark brown lesions. The diseased part is collapsed, yellow or black rot, causing the disease to stagnate. . Grayish white mold is also produced on the petiole and flower stem lesions.
[Pathogen] is a celery fungus Cercosporaapii Fres., is a pathogenic fungus.
[Pathogenesis] The pathogens mainly follow the disease in the field, and when the conditions are appropriate, the overwintering disease produces conidia, which is transmitted by airflow, rainwater and farming operations, and invades from the celery pores or directly penetrates the leaves and stem epidermis. . Celery seeds can also be transmitted by bacteria. In addition, early blight can continue to occur on celery cultivated in the greenhouse, providing a source of bacteria for the onset of celery in the open field. Conidia produced by celery in the open field can also infect shed celery. The onset temperature is 25 Â° C ~ 30 Â° C, high temperature and rain or nighttime dew condensation, early blight is prone to prevalence when the relative humidity is high. In the absence of water, lack of fertilizer, and poor growth of plants, the incidence is also serious. According to the China Pesticide Network , the protection of the wind is not timely, the stagnation of the stagnation of heat, high temperature difference between day and night, easy to dew, the disease is aggravated.
[Control methods] There are differences in disease resistance or disease incidence among breeds. Disease-resistant and light-sick varieties can be used, such as Jinnan Shiqin No. 1, American Utah, Bailey Celery, California King, and Ventura. Seed disinfection. Dilute with hot water at 48 Â° C - 49 Â° C for 30 minutes or hot water for 52 minutes at 52 Â° C, stir while stirring, then transfer to cool water to cool, remove and dry to sow. In order to compensate for the decrease in germination rate, the seeding rate can be increased by 10%. The celery varieties have different heat resistance, so it is advisable to first carry out the soaking test to determine the effect on the germination rate.
At the beginning of the onset of pesticide control, spraying prevention and treatment began. The available effective pesticide fungicides are: 75% chlorothalonil wettable powder 600-700 times liquid, or 30% ether fungus ester water 1000 times liquid, or 50% immunized (fluazidin) 800 times liquid, or 32.5 % spike (benzoxypyrimidine) 1200 times solution, or 50% carbendazim WP 500 times solution, or 72.56 bacteria can be net (Rumocarb) 800 times solution, or 40% tetrachlorodan wettability Powder 500 times solution, or 43% tebuconazole suspension 8000 times solution, or 18.7% enoyl pyrazole ester solution 1000 times solution, or 60% azole ether Â· Daisen water combination 1000 times solution, or 40% more Â·Sulfur suspension agent 500 times liquid, or 72% manganese zinc â€¢ frost urea cyanide water agent 800 times liquid, etc., usually sprayed once every 7-10 days, continuous control 2 to 3 times. The shed celery can be sprayed with 5% chlorothalonil dust (15 kg per hectare) or 6.5% methicillin dust, or 45% chlorothalonil (3 kg per hectare).
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