How to prevent and cure powdery mildew?

Powdery mildew mainly damages wheat leaves, but also stems and ears. It can occur from seedlings to heading. Yellow dots begin to appear on leaves, and then expand and develop into round or oval disease spots. There are white powdery mildew layers on the surface, which interfere with normal metabolism and cause premature senescence. Yield is lost. Let's take a look at how to control powdery mildew.

Symptoms of powdery mildew

Powdery mildew occurs in leaves, tender stems, flower stalks and flower buds, petals and other parts, the initial yellow-green irregular spots, the edge is not obvious. Then the disease spots continue to expand, white spots on the surface, and finally countless black spots. The affected part turns gray, covering its surface continuously, with unclear edges, showing dirty white or pale gray white. When the damage is serious, the leaves shrink and become smaller, the tender shoots are twisted and deformed, and the flower buds do not bloom.

Agricultural control of powdery mildew

1. Select disease-resistant varieties, strictly eliminate infected plants when purchasing seedlings, and eliminate the source of disease. For propagation, cuttings or root shoots without diseases and pests should be cut as asexual propagation materials. When seedlings come out of nursery, pesticide control shall be carried out to prevent sick seedlings from being introduced into new areas.

2. rotate with non-host flowers and trees for 2 to 3 years to reduce the source of disease. Thoroughly clean the nursery, remove dead leaves, cut off diseased branches and destroy them in a centralized manner. During the growth period, the infected branches and leaves shall be removed in time, the fallen leaves shall be thoroughly removed, the diseased branches and over-dense branches in the middle and lower parts shall be cut off, and the branches shall be destroyed in a centralized manner. It is not advisable to plant too densely. Ventilation should be strengthened in the shed to reduce humidity.

3. Remove accumulated water in the field and flower pots in time. Watering should not be too much. Watering should be done from the edge of the pot. Do not sprinkle the stems and leaves, so as to reduce the spread of germs and the chance of disease. Increase phosphorus and potassium fertilizer, less nitrogen fertilizer, so that plants grow robust, apply more fully decomposed organic fertilizer, in order to enhance plant disease resistance.

4. Before planting seedlings of flowers and trees in the greenhouse, thoroughly remove all plants in the shed, clean the shed, and strictly disinfect them by means of drug fumigation. Strictly prevent sick seedlings from entering the room, try to plant a single variety of flowers and trees in the shed, avoid mixed planting, and prevent cross infection. Before budding of flowers and trees in the open field in early spring, the shed can be opened only after the diseased plants in the shed are completely destroyed to prevent the spores from spreading outside the shed.

Chemical control of powdery mildew

1. Spray or coat branches with 3 to 5 degrees of stone sulfur mixture diluent in winter. Note that melon and other vulnerable flowers can not be applied. Sulfur powder is sprayed on the ground, generally using 25 to 30 grams per 70 square meters to eliminate overwintering bacteria.

2, the growth period before the disease can be sprayed with protective agents, after the disease should be sprayed with internal suction agents, according to the symptoms of the disease, flower growth and climate conditions and the characteristics of pesticides, 5 to 20 days interval application once, even 2 to 5 times. A season of flowers and trees, an internal suction agent can only be applied 1 to 2 times. Change pesticide types frequently to avoid resistance.

3. When the disease is full, spray 15% triadimefon 1000 times solution, 2% antimycin 200 times solution, 10% multi-antibiotic 1000 to 1500 times solution. Traditional medicine produces antibody due to repeated use, and the effect is sharply reduced. Therefore, alternate use is advocated. In addition, white wine (alcohol content 35%)1000 times liquid can be sprayed once every 3 to 6 days, continuously sprayed 3 to 6 times, washing leaves until there is no white powder.

4, planted in greenhouses, greenhouses and other protected areas of flowers and trees, in addition to spraying the above-mentioned various agents, but also can apply fumigants and dust agents. Before or after planting, the empty shed shall be disinfected. 250g sulfur powder and 500g sawdust shall be mixed evenly every 100 square meters, divided into 10 piles, ignited with red-hot briquettes or charcoal, and shall not be burned with open fire. The shed shall be closed for one day and night. Fire should be strictly prevented during fumigation. Fumigation of flowers and trees during their growth period is prone to phytotoxicity and should be used with caution. 45% chlorothalonil smoke agent was used before disease onset in plant growth period.