Cucumbers are one of the most popular crops, but farmers often face a serious threat known as "rotten vines" or "stem rot." This disease is particularly concerning when the plants start producing a lot of fruit. If high temperatures and humidity occur at this stage, the entire row of vines can wilt within just a few days, with visible lesions appearing on the stems. The cause of this issue is a fungus from the Ascomycete group, which not only affects the stems but also damages leaves and fruits.
When the stem is infected, oily spots appear near the nodes—oval or prism-shaped, pale grayish-white, slightly sunken, and exuding an amber-like fluid. As the area dries, it shrinks lengthwise, and numerous small black spots form on the surface. The lesions spread quickly in wet conditions, leading to wilting and death of the upper parts of the plant, while the stem rots around the affected areas.
On the leaves, the lesions are typically round, sometimes forming a "V" or semi-circular shape, with colors ranging from pale brown to yellow-brown. These spots are often filled with many tiny black dots. Fruits are usually infected through the flower buds during their early growth stages, resulting in soft, light brown flesh and internal rot.
The main sources of infection include contaminated seeds and soil. Storms, irrigation, and water movement act as carriers for the pathogen. The bacteria enter through stomata, water pores, and wounds, and infected seeds can directly affect the cotyledons. High soil moisture, frequent contact between stems and water, and high relative humidity in the field all increase the risk of disease.
Overcrowded planting, excessive nitrogen fertilizer use, poor air circulation, or insufficient nutrients and weak plant growth can worsen the situation. To prevent cucumber blight, it's best to avoid continuous cropping. Choose well-drained, deep-lying land, add plenty of organic fertilizer, and manage planting density properly.
Before sowing, seeds should be disinfected using 0.3% Bolin solution. Once the disease appears, the following fungicides should be applied immediately:
1. Behenyl or chlorothalonil (40% suspension) diluted 600–800 times.
2. Baoning (60% Duofu WP) diluted 800–1000 times.
3. Thiophanate-methyl (70% wettable powder) diluted 800–1200 times.
All fields should be sprayed every 4–5 days for 2–3 consecutive applications. Additionally, applying the same solutions directly to the stem lesions at a concentration of 50–100 times can significantly improve results. Early detection and timely treatment are crucial for controlling this devastating disease.
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