How to prevent and cure kidney bean gray mold

Kidney beans cultivated in greenhouse and other protected areas are seriously damaged by Botrytis cinerea. First of all, from the kidney bean rhizome upward about 15cm began to appear cloud spots, the surrounding dark brown, the middle light brown to light yellow. When dry, the epidermis of the disease spot is broken and fibrous, and when it is wet, there is a layer of gray Mucor on the disease spot. The disease occurs at the branches, forming small stains, depressions, and then wilting. When kidney bean cotyledons were damaged at seedling stage, water stains became soft and saggy, and white gray mold appeared at the edge of cotyledons gradually. During the podding period, when kidney beans thank flowers, the humidity is high, which infects the wilted Corolla and causes kidney beans to drop pods. When infecting leaves, 1-2cm waterlogged irregular dark brown patches appeared.

Grey mold disease

Infection. The pathogen of kidney bean gray mold is the same as tomato and cucumber, conidia accumulate, colorless unit cell, great difference between the two ends, like water droplets. Sporophore light brown, septate. Under suitable temperature and humidity, the pathogen of Botrytis cinerea produces a large number of sclerotia. The sclerotia has strong stress resistance and long survival time. Once it meets the right temperature and humidity again, it will grow hyphae or spore peduncles, directly infect kidney bean plants and spread the harm. The disease can be caused by rotten diseased fruits, diseased leaves, diseased tendrils and decaying diseased flowers falling on healthy parts of kidney beans.

The condition of occurrence. The mycelium could grow at 4: 32 ℃, and the optimum temperature was 13: 21 ℃. The temperature for spore production was wide, and the optimum temperature was 21: 23 ℃. When the air relative humidity is more than 90%, the spores fly away and spread the disease. The spore germination temperature is 5: 30 ℃, and the optimum temperature is 13-29 ℃. Higher humidity is needed for spore germination, and spores do not germinate when the humidity is less than 90%. Bacterial infection generally weakens the resistance of the host disease at first, and then causes kidney bean rot and mildew. As long as the air humidity is high and the temperature is about 20 ℃, Botrytis cinerea is very easy to be prevalent in greenhouse production.

Prevention and treatment. Botrytis cinerea has the advantages of fast infection, long incubation period, easy to produce drug resistance and difficult to control, so it needs the combination of agricultural control and chemical control. To strengthen the environmental control under the condition of greenhouse, timely application of water and fertilizer, strengthening ventilation and dehumidification, and suitable temperature should be helpful to control the occurrence and spread of diseases. Remove diseased leaves and pods manually in time, take them out of the shed and destroy them thoroughly and bury them deeply. When kidney beans appear sporadic diseased leaves, spray control. The commonly used agents are 50% Sukeling wettable powder 1 000 times 1 500 times, or 50% prohydantoin wettable powder 1 000 times 1 200 times, once every 5-7 days, 2 times in a row. According to the experiment, the effect of spraying powder is better than spraying, the investment is small, the time effect is long, with 5% carbendazim, 1.5 kg per mu, the disease can be controlled.