Anthracnose is one of the most prevalent and serious diseases affecting watermelon crops. It is widely distributed across watermelon-growing regions in the country, particularly in the humid southern areas where heavy rainfall creates favorable conditions for its spread. This disease significantly impacts the stable production, yield, and quality of watermelons, making it a major concern for farmers.
The symptoms of anthracnose can appear at various growth stages, from seedlings to mature plants, and affect leaves, vines, and fruits. When seedlings are infected, the stems near the soil surface turn dark brown and collapse. On the leaves, the initial symptoms are small, yellow, water-soaked spots that gradually enlarge into brown lesions. A purple-black border forms around the spot, with small black dots or pink, sticky masses appearing on the surface. As the lesions grow, they merge into larger patches, leading to leaf death when dry. On petioles and vines, narrow brown depressions develop, which can cause the stems to die if left unchecked. If the fruit stem is infected, the young fruit becomes dark and shrivels, eventually dying. On mature fruits, the disease starts as a water-soaked ring, followed by a crater-like spot with concentric rings of small spots. The affected area is covered with pink, sticky spores, and severe infections lead to deformed fruit, extensive lesion fusion, and eventual rotting.
To manage anthracnose effectively, several preventive and control measures should be implemented. First, selecting resistant varieties is crucial. Varieties such as Qingfa No. 8, Humidity-proof 8802, Huami No. 8, Qingnong No. 5, Huami No. 10, Zhengkang No. 7, Extra-large Zhengkang No. 3, Qingfa No. 12, and Lubao Golden Flower King have shown strong resistance to the disease. Seed treatment before planting also plays an important role. Soaking seeds in a 0.1% potassium permanganate solution for 5–6 hours or in a 100-fold diluted agricultural streptomycin solution for 10 minutes can help prevent infection. After soaking, rinse the seeds thoroughly with water 3–4 times before sowing.
Crop rotation is another effective strategy. In paddy fields, a 3–4 year rotation period is recommended, while in dry lands, a 5–6 year interval is advised. Applying well-decomposed organic manure along with phosphorus and potassium fertilizers, while reducing nitrogen input, helps improve plant resistance. Additionally, using deep furrow and mulch film techniques can lower soil moisture and humidity, creating an environment less favorable for pathogen development.
Field management practices, such as proper pruning, pinching, and maintaining good air circulation, are essential. Avoiding flood irrigation also reduces the risk of disease spread. Chemical control measures should be applied early in the disease cycle for best results. Fungicides like 70% thiophanate-methyl (600x), 15% pyrethroid (1000x), 20% carbendazim (3000x), 60% chlorothalonil (500x), or 80% benzothiadiazole (800x) can be used. Alternatively, 70% mancozeb at 500x concentration is also effective. Spraying every 7 days and alternating between different fungicides can enhance the control effect.
Author unit: Vegetable Station of Malipo County Agriculture Bureau, Yunnan Province.
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