Watch out for the rainy season
Watermelon blight, also known as Phytophthora, is a serious fungal disease that affects both seedlings and mature watermelon plants. This soil-borne disease thrives in high humidity and warm conditions, making it particularly prevalent during the late growth stages of the plant. The disease often becomes severe following heavy and prolonged rainfall, especially when the rainy season starts early. The timing of the outbreak is usually closely linked to peak rainfall periods, leading to significant crop losses if not managed properly.
The symptoms of the disease are quite distinct. On the leaves, dark green, round or irregularly shaped water-soaked spots appear, which can quickly turn into soft, rotten areas resembling scalded tissue under high humidity. In dry conditions, these lesions become light brown and brittle, easily breaking off. At the base of the vines, spindle-shaped, water-soaked, dark green spots develop, eventually causing the stem to rot and the entire plant to die.
On the fruit, the disease manifests as dark green, water-soaked depressions that rapidly expand, leading to full fruit rot. Affected fruits emit a sour, fermented odor, and a dense layer of white mycelium appears on the surface.
To prevent and control this disease, it's important to act early. Apply fungicides such as 50% mancozeb wettable powder diluted at 700–800 times, 72.2% propamocarb hydrochloride at 800 times, 64% acibenzolar-S-methyl WP at 500 times, or 58% metalaxyl-Mn zinc wettable powder at 500 times. Spray every 7–10 days, and repeat up to 3–4 times if necessary. For better results, the same solution can be used for root irrigation, applying 0.4 to 0.5 liters per plant. Combining foliar sprays with root drenching enhances the effectiveness of the treatment.
Regular monitoring and timely application of preventive measures are crucial in managing Phytophthora in watermelon crops. Early intervention can significantly reduce the risk of severe outbreaks and protect yield quality.
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