The new leaves of the bitter gourd plant have become narrow, elongated, shriveled, hardened, and twisted. The affected plants are significantly stunted, making it difficult for fruits to develop properly. Even when fruits do form, they are often deformed, hardened, and show mottling on their surface. Recently, a local farmer brought a diseased bitter gourd vine to the plant protection station, seeking help to identify the issue and find solutions. He was clearly worried and asked me to explain what might be causing the problem.
From my understanding, since the farmer did not use hormones or excessive pesticides in the early stages of growth, this is likely a case of bitter gourd virus disease. Based on the symptoms observed, it seems to be the yellowing and shrinking type of viral infection.
Bitter gourd virus disease is one of the most common and widespread diseases affecting the crop. It occurs in both open fields and greenhouses, with higher incidence during the summer and autumn seasons. On average, the disease affects 5-10% of crops, but under severe conditions, the rate can exceed 15%, which greatly impacts yield and fruit quality.
When the disease occurs, the entire plant is usually affected, mainly targeting the leaves and growing tips. The top shoots show clear signs of infection. In addition to the yellow and wrinkled variety, there's also a mosaic-type virus, which causes yellow and green mottling on the upper leaves, uneven leaf surfaces, deformed and hardened new leaves, shortened internodes at the top, and reduced flower fertility. Fruits may fail to set or develop abnormally, resulting in deformed produce.
This disease thrives in hot, sunny, and dry conditions. Overcrowded planting, weed infestation, nearby melon crops, and high locust populations can all contribute to its spread. Additionally, water shortages, poor soil fertility, and weak plant growth make the plants more susceptible to infection.
Currently, there is no effective treatment that can completely eliminate the virus. However, prevention and control measures can help reduce its spread. First, controlling insect vectors like aphids and whiteflies is crucial. You can spray 25% Actara wettable powder diluted 6000–8000 times, 70% Imidacloprid wettable powder at 10000–15000 times, or 5% Imidacloprid emulsifiable concentrate diluted 2500–3000 times. Focus on spraying the underside of leaves and the growing points.
Second, applying a virus inactivator such as 20% Virus A wettable powder at 400–600 times, or 1.5% Lingzhiling emulsion at 1000 times, every 7–10 days for 2–3 applications, can help boost the plant’s resistance. You can also use a 0.1% potassium permanganate solution or Antitoxin No. 1 diluted 300 times. In the early stages, spraying 5% Mycorrhizal Bactericidal Agent at 200–300 times once or twice can also be beneficial.
During field work such as pruning, harvesting, and tying vines, it's important to separate diseased and healthy plants to avoid spreading the virus manually. This helps minimize cross-infection.
In regions where bitter gourds are grown year-round and viral diseases are common, proactive measures should be taken. These include selecting virus-resistant varieties, using seeds from healthy plants, disinfecting seeds before sowing, covering with medicinal soil after planting, applying insecticides before transplanting, and maintaining proper moisture levels. Increasing humidity, reducing pest infestations, and using growth-promoting bacteria or phytoalexins can also help. A mixture of potassium dihydrogen phosphate, black soap, and laundry soap in a 1:1:250 ratio can be sprayed every 5–7 days, up to 4–5 times, for added protection.
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