The new leaves of the bitter gourd plant have become narrow, elongated, shriveled, hardened, and twisted. The affected plants are visibly stunted, making it hard for fruits to develop properly. Even when fruits do form, they tend to be deformed, tough, and mottled on the surface. Recently, a farmer came to the plant protection station with a diseased bitter gourd vine, clearly worried about what was happening to his crop. He was seeking advice from both the station and the author to identify the problem and find a solution.
The author believes that since the farmer did not use hormones or excessive pesticides in the early stages of growth, the issue is likely due to a viral infection. Based on the symptoms, it seems to be the yellowing and shrinking type of virus disease commonly seen in bitter gourds.
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 incidence 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, especially the leaves and growing tips. Symptoms include yellowing, wrinkling, and curling of the leaves, along with deformities in new growth. Some strains cause mosaic patterns, with yellow and green spots appearing on the leaves, leading to uneven leaf development. The young shoots at the top may also show signs of stunting, with shortened internodes, reduced flowering, and poor fruit set. When fruits do develop, they often become misshapen and hard.
The disease thrives under high temperatures, intense sunlight, and dry conditions. Poor management practices, such as excessive weed growth, proximity to other melon crops, and heavy infestations of pests like aphids, can worsen the situation. Additionally, water stress, nutrient deficiency, and weak plant growth can make the plants more susceptible to infection.
Currently, there is no known treatment that can completely eliminate the virus. Prevention is the key. One approach is to control insect vectors, such as whiteflies and aphids, which transmit the virus. Insecticides like 25% Actara wettable powder (diluted 6000-8000 times), 70% Imidacloprid wettable powder (10000-15000 times), or 5% Imidacloprid emulsion (2500-3000 times) can be applied, focusing on the back of leaves and growing points.
Another method is to apply virus-inactivating agents, such as 20% Virazole wettable powder (400-600 times) or 1.5% Lingzhiling emulsion (1000 times). These should be sprayed every 7-10 days, with 2-3 applications in total. Other options include 0.1% potassium permanganate or Antitoxin No. 1 (300 times), which can help boost the plant’s resistance to the virus.
In the early stages of infection, applying 5% Mycorrhizal Bactericidal Agent (200-300 times) 1-2 times can also provide some relief. During field operations like pruning, harvesting, and tying vines, it's important to avoid spreading the virus by keeping infected and healthy plants separate.
In areas where bitter gourd is grown year-round and viral diseases are common, prevention must start early. Farmers should choose resistant varieties, collect seeds from healthy plants, disinfect seeds before planting, and use treated soil. Applying insecticides before transplanting, maintaining proper moisture levels, reducing pest populations, and using bio-stimulants like phytoalexins or growth promoters can help. A mixture of potassium dihydrogen phosphate, black soap, and laundry soap (1:1:250) can also be sprayed every 5-7 days, up to 4-5 times, to improve plant health and reduce virus impact.
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