Rape downy mildew
Symptoms Rape downy mildew is an important disease in all areas of rapeseed in China. The damage in the Yangtze River basin and the southeast coast is heavy. Spring rapeseed areas are less frequent and lighter. The disease mainly damages leaves, stems and pods, causing the victim to turn yellow and grow white mold. The pedicel became swollen and curved at the top of the disease, showing a "head-turning" shape. The petal hypertrophy turned green and was not strong, resulting in a white frosty mould. The leaves began to appear light green spots, and later expanded into polygonal yellow patches, the back of the leaves grow white mold.
The pathogen Peronospora parasitica (Pers.) Fr. (synonyms P. brassicae Gaumann) called parasitic fungi, flagellin subphylum fungi. The mycelium is colorless and does not have a septum. It spreads between cells. It absorbs moisture and nutrients by sucking into the cells. The blister is shaped like a pear or stick. The cyst stems growing from the hyphae stick out from the stomata. They are solitary or 2-4 bunches. They are colorless and undivided. The trunk base is slightly larger and is made of repeated bifurcated branches. The top is 2-5 times. Branches, 154.5-515 μm in length, the main axis and branches are in sharp angles, and the small ones at the top are sharp and curved, with one sporangium per end. The sporangia are colorless, single cells, oblong to oval, 19.8-30.918-28 (μm) in size. When germinating, they often produce germ tubes from the side and do not form zoospores. Oval spore spherical, unit cell,
Yellow-brown, smooth surface, size 27.9-45.3μm, egg diameter 12.4-27.5μm, cell wall thickness, surface shrinkage or smooth, strong resistance, if conditions are appropriate, can directly generate germ tube infection. The strain is a parasite that can only survive on living organisms and has obvious physiological differentiation. It is reported that the three species of the genus Peronus, Radish, and Viola in the cruciferous families of Cruciferae in China are different, and the main difference is their respective infective abilities. The genus of this genus has strong invasiveness to this genus, and has weak invasiveness to radish and is not easy to infect leeks; radish is a variant that has strong invasiveness to radish and weak infectivity to genus Amaranthus, does not infect leeks; Varieties, only infect leek, do not infect other cruciferous plants. Among the pupa species, according to the pathogenicity difference, they were divided into 6 physiological races. The rapeseed cultivars belonged to the cultivar No. 1 and were specialized for PPfrapiferae. Rape strains produced the optimum temperature for sporangia 8-12°C. The temperature of sporangium germination was 7-13°C, the highest temperature was 25°C, the lowest was 3°C, and the infection temperature was 16°C. The optimum temperature for the growth and development of mycelia in the plant body is 20-24°C. The oospores are easy to form under the condition of 10-15°C and relative humidity of 70%-75%.
Transmission routes and conditions In winter rapeseed areas, the germs use oospores to grow in the soil, in the manure, and in the seeds during the summer, after the germination in the autumn, the seedlings are infested, and sporangia are formed on the lesions to re-infect. Diseases in winter are unpleasantly spread, and hyphae are used to overwinter in diseased leaves. The temperature in late spring increases, and sporangia produce infested leaves, stems and pods again through rain and rain. The rapeseed enters mature stage and the diseased department produces oospore. Can be repeatedly infested. Long-distance transmission mainly depends on the oospore mixed in the seeds. As for near-distance transmission, oospore mixed in seeds and manure is directly transmitted to the sick fields, and is mainly spread by airflow, irrigation water or rainwater. The sporangia radiates from the tips of small stems to airborne due to the shrinkage of the cyst stems.
Spread to the healthy plants, the propagation distance is 8-9m, and the oospores on the debris in the soil flow through the water. The sporangia produced after germination are splashed onto the healthy seedlings with rain. The temperature of sporangia formation is 8-21°C, the optimum temperature for infection is 8-14°C, and the relative humidity is 90%-95%. It has been reported that it germinates at 4-6 hours below 15°C and adhering to sporulation at 12 hours. The illumination time is less than 16 hours. The cotyledon stage of the seedlings can infect. The degree of infection is positively correlated with the number of sporangia. The sporangia falls on the susceptible host. The temperature is suitable to produce the bud tube first and the adventitious cell grows into the invasive silk. Invasion through the stratum corneum, sometimes through stomatal invasion, mycelial invasion extends to 7-8μm, and grows in the mesangial zone between the peristaltic wall of the epidermis, and then branches in cells in all directions, in the host cells. There is a long suction device. Observed under the electron microscope, the cell wall initially in contact with the mycelium partially expanded and appeared a microfibril structure. The branch of the inhaler penetrated through a hole of 1-2 μm in size and formed a bacillus ring structure around the base of the stimulator. When the sweller swelled, the host was generated. Sheathing of the plasma membrane. When the nutrients in the cells have been consumed, the cells begin to die, showing yellowing or dead tissue. The occurrence of the disease is closely related to climate, species and cultivation conditions. The temperature is 8-16°C, relative humidity is 90%, and weak light is conducive to the infection of the bacteria. The production of low temperature, rain, high humidity, and less sunlight contribute to the occurrence of diseases. The winter temperature in the rapeseed area of ​​the Yangtze River basin is low, and the incidence of rain is light. The temperature in spring rises, and the rainfall is high. The humidity in the field is often susceptible to disease or causes the epidemic of the disease during flowering. Continuous cropping, early sowing, partial application of nitrogenous fertilizers or potassium-depleted plots, and high density and moisture retention plots in the field are prone to disease. Low-lying land, poor drainage, planting cabbage, or mustard-type rape are more serious.
Control methods (1) Plant disease-resistant varieties according to local conditions. Such as Zhongshuang 4th, Liangyou 586, Qinyou 2, Baiyou 1, Qingyou 2, Huyou 3, Xinyou 8, Xinyou 9, Rongyou 3, Jiangyan 1, Grease No. 4 and so on. Promote the cultivation of Brassica napus, such as Brassica napus L. or Brassica napus, and other disease resistance. (2) Promoting a two-year rotation with grassy crops such as big wheat can greatly reduce the amount of oospores in the soil and reduce the source of bacteria. (3) Seed dressing with 1% of the seed weight of 35% thioredoxin or metalaxyl. (4) It is not too early to strengthen field management and achieve proper sowing. Determine the reasonable density based on the fertility of the soil and the variety characteristics. Using formula fertilization technology, reasonable application of nitrogen, phosphorus and potassium fertilizers to improve disease resistance. Drain the water promptly after the rain to prevent moisture retention and flooding. (5) Focus on the prevention and control of dryland cultivation of cultivated Chinese cabbage rape, generally in early March in the convulsing period to investigate the condition of the disease, when the disease rate of 20% or more, began to spray 40% cream Epimedil wettable powder 150-200 Diluent or 75% chlorothalonil wettable powder 500 times, 72.2% Precive 600-800 times, 64% antiseptic M?8 wettable powder 500 times, 36% lupestar suspension 600-700 Times of liquid, 58% metalaxyl MnZn WP 500 times, 70% EB MnZn WP 500 times, 40% chlorothalonil suspoemulsion 600 times, spray every 667m? Liquid 60-70L, once every 7-10 days, continuous control 2-3 times. In downy mildew, white spot mixed areas, 40% cream WP can be used 400 times and 25% carbendazim WP 400 times. In downy mildew and black spot mixed areas, 90% triethylphosphonate wettable powder 400 times liquid plus 50% aprotinine wettable powder 1000 times liquid or 90% triethylphosphonate aluminum wettable powder can be used 400 times liquid plus 70% mancozeb WP 500 times, both prevention and excellent effect. The area where resistance to the above fungicides can be used can be changed to 72% DuPont Kelu, 72% clenbuterol, 72% frost urea manganese zinc or 72% frost WP wettable powder 600-700 times. Promote the application of 69% Anke manganese zinc wettable powder 900-1000 times liquid.
Beef Jerky Sticks,Chomps Beef Sticks,Beef Jerky Sticks Bulk,Teriyaki Beef Jerky Sticks
Jiangxi Welton Pet Products Co., Ltd. , https://www.weltonpetcare.com