1. Symptoms of Damage: This disease primarily affects flowers and young fruits. In the case of flower bud infection, the buds gradually soften, wither, and rot. A dense layer of brown fungus forms on the buds and receptacles, leading to the eventual falling off of infected flowers or, in some cases, their retention on the plant. These retained flowers can lead to infections in young fruits. When the disease affects young fruits, it begins with small, light green circular spots on the fruit surface. As the lesions expand rapidly, the color changes to dark brown, causing the fruit to stop growing. Severe cases result in fruit rot, and the affected fruits eventually shrink and remain hanging on the branches like dried-up fruits.
2. Control Methods
(1) Before warming up the greenhouse, it is essential to thoroughly clean the garden area and deepen the tree trays to reduce the initial sources of infection.
(2) Proper thinning of flowers and fruits is important to minimize contact transmission caused by field activities such as artificial pollination, especially when there are too many flowers and fruits.
(3) Diseased flowers, fruits, and any remaining flower parts on young fruits should be removed promptly to prevent the spread of the disease. Before the onset of gray mold, diseased flowers and fruits should be carefully picked and placed in sealed plastic bags, then taken outside the greenhouse for burial or incineration.
(4) Careful management of irrigation is crucial. Watering should be done on sunny days only, avoiding cloudy days. During the morning, maintain high temperatures inside the greenhouse to quickly evaporate dew from the top. In the afternoon, extend the ventilation time to increase air circulation and reduce humidity. Even if there are many cloudy days and low temperatures during flowering and fruit development, proper ventilation must still be maintained. Additionally, mulching can significantly help in reducing the occurrence of gray mold.
(5) Limit the use of nitrogen fertilizers to prevent excessive growth of new shoots, which can create favorable conditions for the disease. Ensure good ventilation within the orchard to further reduce the risk of infection.
(6) It is best to avoid intercropping plants that are highly susceptible to gray mold, such as canola, lettuce, and peppers, in the greenhouse environment.
(7) Apply a preventive fungicide before spraying. After flowering, spray once every 10 days, repeating this process 2–3 times. Rotate different fungicides to prevent resistance. Recommended agents include: 50% Carbendazim WP diluted at 1500 times, 50% Benomyl wettable powder at 1200 times, 65% Triadimefon WP at 1000 times, 50% Bleomycin wettable powder at 600 times, or a mixture of 50% Carbendazim 500 times and 50% Thiram 500 times. Another option is a combination of 75% Chlorothalonil 600 times and 70% Mancozeb 500 times. Additionally, before the disease appears, you can use fast-spraying smoke agents for fumigation treatment at a rate of 300 grams per mu.
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