Powdery mildew on green radish. I planted dozens of acres of green radish in Guangzhou. During this time, my green radish seemed to be infected with powdery mildew.

Prevention and treatment methods found on the Internet! Growers on both sides of Longxi Avenue pay attention to the occurrence of cross-infection of diseases caused by the same irrigation water source!

1． Incidence pattern: Powdery mildew mycelium overwinters on diseased buds, branches or fallen leaves, and can occur year-round in the greenhouse. When the temperature rises the following spring, the germs are spread by airflow or water droplets. When the spring temperature in the open field is around 20°C, powdery mildew begins to grow and develop, and produces a large number of conidia to spread and infect the plants. When the temperature and humidity are high in summer, a large number of conidia will be produced, which will expand and infect again. The conidia will germinate in the leaves and enter the tissues from the leaf stomata to absorb nutrients from the leaves. . In terms of cultivation and management, excessive nitrogen fertilizer application, excessive watering, and too dense planting are suitable conditions for the occurrence of this disease mainly in an environment with insufficient light, poor ventilation, high air humidity, excessive application of nitrogen fertilizer, calcium deficiency or excessive dryness. Light sandy soil, drastic temperature changes, and excessively dry soil in flower pots are all conducive to the occurrence of the disease.

2 The prevention method is to have sufficient light, ventilation, frequent fertilization, and spray copper sulfate soap solution or crude sodium carbonate solution (4-5g dissolved in 1L water) on diseased plants for prevention and control. Spray diseased plants with a fertilizer mixture.

To prevent and control plant diseases, you can also use garlic juice (25g of crushed garlic mixed with 1L of water and soaked for one day and night), and wash the plants every 6 days. You can also spray a mixture of 1g salicylic acid, 3g alkali, 5mg denatured alcohol, 10g soap and 1L water, dilute it 3 times before use.

3． Prevention and control methods: Strictly disinfect the soil and utensils used, and use materials that do not contain pathogenic bacteria for planting. When purchasing seedlings, disease-infected plants must be strictly eliminated to eliminate the source of the disease. When propagating, it is necessary to cut disease and insect-free cuttings or root tillers as vegetative propagation materials. Cultivation varieties If possible, try to choose disease-resistant varieties. For timely pruning of diseased branches, diseased buds, and diseased leaves, and cleaning of rotten branches and leaves in the garden to reduce the source of infection; strengthen cultivation management, and avoid excessive planting density and potted flower placement; pay attention to ventilation and light transmission; increase phosphorus application Potassium fertilizer and nitrogen fertilizer should be appropriate; spray Baume 2~4 degree lime sulfur mixture during the dormant period, and during the growing season, spray 70% Tropezin Methyl Wettable Powder 700~800 times liquid or 50% Desenium 800~1000 times Liquid or 50% carbendazim wettable powder 500~1000 times liquid. Sulfur powder is very effective in preventing powdery mildew and is often used in greenhouses. The sulfur powder can be left to volatilize on heating equipment, or a heater (such as the heat from a light bulb) can be used to volatilize the sulfur powder. The appropriate temperature for using sulfur powder is 15~30℃, and it is best to do it in the evening to avoid injuries during the day. After the onset of the disease, promptly cut off the infected branches and leaves and burn them, then spray 50% carbendazim with an application interval of 10 to 15 days.

In production practice, there are mainly the following ways to prevent and control powdery mildew.

(1) Crop rotation with non-host flowers and trees for 2 to 3 years to reduce the source of the disease.

(2) Strengthen cultivation and management. During the overwintering period from late autumn to early spring of the following year, nurseries should be thoroughly cleaned, dead branches and leaves removed, and diseased and insect-infested branches cut off and destroyed centrally. During the growth period, timely remove infected branches and leaves, thoroughly remove fallen leaves, cut off diseased branches and excessively dense branches in the middle and lower parts, and destroy them collectively. It is not advisable to plant too densely, and the greenhouse should be ventilated to reduce humidity. Eliminate accumulated water in fields and flower pots in a timely manner. Watering should not be excessive. Water from the edge of the pot to avoid watering the stems and leaves to reduce the spread of germs and the chance of disease. Apply more phosphorus and potassium fertilizers and less nitrogen fertilizers to make the plants grow strong, and apply more fully decomposed organic fertilizers to enhance the disease resistance of the plants.

(3) Prevent the disease of flowers and trees in the greenhouse. Before planting seedlings in the greenhouse, thoroughly remove all plants in the greenhouse, clean the greenhouse, and strictly disinfect with chemical fumigation and other means. Strictly prevent diseased seedlings from entering the house, try to plant a single variety of flowers and trees in the shed, and avoid mixed planting to prevent cross-infection. In early spring, before the flowers and trees sprout in the open field, the shed can be opened only after thoroughly destroying the diseased plants in the shed to prevent the spread of spores outside the shed.

(4) During the overwintering period, spray or paint the branches with Baume 3 to 5 degree diluted lime sulfur mixture. Note that flowers susceptible to pesticide damage, such as cineraria, cannot be applied. Spray sulfur powder on the ground, usually 25 to 30 grams per 70 square meters, to eliminate the sources of overwintering bacteria.

(5) During the growth period, protective agents can be sprayed before the onset of the disease, and systemic agents should be sprayed after the onset of the disease. According to the symptoms of the disease, the growth and climate conditions of flowers and trees, and the characteristics of the pesticide, pesticides should be applied every 5 to 20 days. , apply 2 to 5 times continuously. A systemic agent can only be applied 1 to 2 times per season to flowers and trees. Pesticide types should be changed frequently to prevent germs from developing resistance.

(6) Frequently used protective agents include 50% sulfur suspension agent 500 to 800 times liquid, 45% lime sulfur crystal mixture 300 times liquid, 50% antibacterial wettable powder 800 times liquid, 75 times liquid % chlorothalonil 500 times solution, 70% mancozeb 400 times solution.

(7) Systemic agents include 50% carbendazim 500 times solution and 75% thiophanate methyl 1000 times solution. When the disease is in full bloom, you can spray 15% fentanin 1000 times.

(8) Antibiotics include 2% antimycin aqueous solution 200 times, 10% polymycin (Polyan) 1000 to 1500 times solution.

(9) Other drugs include baking soda 500 times, which can be sprayed every 3 days in the early stage of the disease, and sprayed 3 to 6 times continuously.

In addition, you can also use 1000 times of liquor (alcohol content 35%), spray once every 3 to 6 days, spray 3 to 6 times continuously, and rinse the leaves until there is no white powder. For flowers and trees planted in greenhouses, greenhouses and other protected areas, in addition to spraying the above-mentioned chemicals, fumigants and dusts can also be applied. The empty shed must be disinfected before or after planting. Use 250 grams of sulfur powder and 500 grams of sawdust per 100 square meters, mix evenly, divide into 10 piles, ignite with red-hot briquettes or charcoal, do not burn with open flames, and close the shed for a day and night. Be careful about fire during the fumigation process. Smoking during the growth period of flowers and trees is prone to phytotoxicity and should be used with caution. During the plant growth period, before the onset of disease, use 45% chlorothalonil fumigation agent at 25 grams per 67 square meters or spray 5% chlorothalonil dust at 100 grams per 67 square meters.