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 pathogen thrives in warm and wet conditions, making it particularly problematic during the late growth stage of the plant. The disease tends to occur more frequently when the rainy season starts early, lasts for an extended period, and involves heavy rainfall. As a result, the outbreak occurs earlier and becomes more severe, leading to significant crop losses.
The symptoms of the disease vary depending on the part of the plant affected. On the leaves, dark green, round or irregularly shaped water-soaked spots appear, which may become soft and sunken when humidity is high. In dry conditions, the lesions turn light brown and easily break apart. 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.
When the fruit is infected, dark green, water-soaked depressions form on the surface. These spots quickly expand, leading to full fruit rot with a fermented odor. A dense layer of white mycelium often covers the diseased area, further indicating the severity of the infection.
To manage this disease effectively, early intervention is crucial. Farmers can apply fungicides such as 50% mancozeb wettable powder diluted at 700–800 times, 72.2% propamocarb hydrochloride at 800 times, 64% triazoxide WP at 500 times, or 58% metalaxyl-Mn wettable powder at 500 times. Spraying should be done every 7–10 days, and multiple applications (3–4 times) may be necessary for best results. In addition, the same solutions can be used to drench the roots, applying 0.4 to 0.5 liters per plant. Combining foliar sprays with root irrigation usually provides better control and helps reduce disease spread. It's important to monitor weather conditions and act promptly to prevent widespread damage.
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