In recent days, a farmer approached the plant protection station with concern, holding a diseased bitter gourd vine. He was worried about the strange symptoms appearing on his plants and sought advice from both the station and the author to identify the issue and find a solution. The affected vines showed signs of new leaves becoming narrow, elongated, curled, hardened, and twisted. The plants were significantly stunted, making it difficult for fruits to develop properly. Even when fruits did form, they were often deformed, hard, and mottled on the surface.
The author believes that since the farmer didn’t use hormones or excessive pesticides earlier, the problem is likely due to a viral infection. Based on the symptoms, it appears to be a yellowing and shrinking type of viral disease commonly seen in bitter gourd crops.
Bitter gourd virus disease is one of the most common and widespread diseases affecting this crop. It occurs in both open fields and protected environments, with higher prevalence during summer and autumn. On average, the disease affects 5–10% of the plants, which can impact yield and quality. In severe cases, the infection rate can exceed 15%, causing significant losses in production.
The disease typically affects the entire plant, with the leaves and growing tips being the main targets. Symptoms include yellowing, wrinkling, and curling of the leaves. There are different types of viral infections, such as mosaic virus, which causes irregular yellow and green spots on the leaves, leading to uneven leaf development. New leaves may become deformed, hard, and the top internodes may shorten. This results in sterile flowers, poor fruit set, or malformed fruits.
The disease thrives under high temperatures, strong sunlight, and drought conditions. Excessive weeds, nearby melon crops, and heavy locust infestations can also contribute to its spread. Additionally, water shortages, nutrient deficiencies, and weak plant growth increase susceptibility to the virus.
Currently, there are no effective chemical agents that can completely eliminate the virus, so prevention is key. One approach is to control insect vectors like aphids and whiteflies, which transmit the virus. Insecticides such as 25% Actara wettable powder (diluted 6000–8000 times), 70% Imidacloprid wettable powder (10000–15000 times), or 5% Imidacloprid emulsion (2500–3000 times) can be used, focusing on the back of the leaves and the growing tips.
Another method is to apply virus inactivation agents, such as 20% Virup wettable powder (400–600 times), 1.5% Lingzhiling emulsion (1000 times), or 0.1% potassium permanganate solution. These can help improve the plant’s resistance to the virus. Spraying 5% mycorrhizal bactericidal agent at 200–300 times in the early stages can also be beneficial.
During field operations like pruning, harvesting, and tying vines, it's important to separate diseased and healthy plants to avoid human transmission of the virus. This helps reduce cross-infection.
In areas where bitter gourd is grown year-round and viral diseases are common, proactive measures should be taken. These include selecting disease-resistant varieties, using seeds from healthy plants, disinfecting seeds before sowing, covering with medicinal soil, spraying insecticides before transplanting, maintaining proper moisture levels, reducing pest populations, applying growth-promoting bacteria, and using solutions like a mixture of potassium dihydrogen phosphate and black soap (1:1:250 ratio). Repeating these treatments every 5–7 days for 4–5 times can help manage the disease effectively.
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