Detailed Explanation of the Latest Control Methods for Cucumber Gray Mold
Cucumber gray mold is a disease that occurs year after year in protected cucumber cultivation. It is caused by infection with the fungus Botrytis cinerea of the Deuteromycotina (Fungi Imperfecti), and vegetable growers often call it fruit rot or moldy rot. In recent years its incidence has become more severe year by year, because the fruit is often affected and causes rot. Now let us take a look at the control methods for cucumber gray mold!
Symptoms of Cucumber Gray Mold
Cucumber gray mold mostly begins infecting from spent female flowers. Initially, water-soaked lesions appear at the flower base, and a grayish-brown mold layer gradually grows, causing the floral organs to soften, shrivel and rot, and gradually spreading to the young cucumber. The diseased part of the fruit first turns yellow, and later produces white mold that gradually turns pale gray, causing the diseased cucumber to stop growing, soften, rot and shrivel, and finally rot and drop off. When leaves are infected, the lesions are initially water-soaked, then become irregular light brown lesions with distinct edges, and sometimes a small amount of grayish-brown mold layer grows on the lesions. Under high humidity conditions, the lesions expand rapidly, forming large lesions 15-20 mm in diameter. When stems and vines are infected, the stems rot and the vines break, causing the plants to rot.
Occurrence Pattern of Cucumber Gray Mold
The pathogen overwinters as mycelium, conidia and sclerotia attached to diseased plant residues or left in the soil, and spreads through wind and rain and agricultural operations. The fruiting stage of cucumber is the peak period for pathogen infection and disease occurrence. It is prone to occur under high humidity (relative humidity above 94%), relatively low temperature (18-23°C), insufficient light and weak plant growth. When the temperature exceeds 30°C and the relative humidity is below 90%, the spread stops. Therefore, this disease mostly occurs in greenhouses with low temperature and scant light in winter.
Control Methods for Cucumber Gray Mold
1. Remove diseased plant residues: In the late harvest period, thoroughly remove diseased plant residues, deep-plow the soil more than 20 cm, turn the diseased residues left on the soil surface into the lower layers, and spray a soil disinfectant plus New High-Lipid Film to disinfect the soil, reducing the initial infection sources in the greenhouse. During the seedling stage and before the cucumbers swell, promptly remove diseased flowers, diseased cucumbers and diseased leaves, take them out of the greenhouse and deep-bury them, reducing the sources of re-infection.
2. Strengthen cultivation management: Strengthen ventilation and air exchange, water moderately, avoid watering on cloudy days, prevent excessively high temperatures, pay attention to keeping warm, and prevent cold waves from invading. In hot seasons, deep-plow and irrigate in the greenhouse, remove floating matter from the water surface, and deep-bury or burn it in a centralized manner to keep the greenhouse clean.
3. Regulate temperature and humidity: In planting greenhouses, regulating temperature and humidity can control pathogen infection. Raise the indoor temperature to 31-33°C, begin ventilating when it exceeds 33°C, maintain the temperature at 20-25°C in the afternoon, close the vents when it drops to 20°C, and keep the nighttime temperature at 15-17°C.
4. Disinfect and sterilize the greenhouse. Before planting in a seedling greenhouse or production greenhouse, use 5% procymidone smoke agent at 1 kg per mu for closed-house fumigation for 24 hours, and spray thoroughly with 40% pyrimethanil suspension concentrate at 1000-1500 times dilution, or 50% iprodione suspension concentrate or wettable powder at 800 times dilution, or 70% thiram at 300 times dilution.