Potato wilt
Early symptoms of the disease include wilting. When you cut open the affected stems, you'll notice that the vascular bundles of the tubers turn brown. In high humidity conditions, the disease often produces white to pink fungal mycelia on the surface.
The pathogen responsible for this disease is *Fusarium oxysporum* Schlecht. (Schlecht.), commonly referred to as *Fusarium* spp. The mycelium appears gray-brown in color. Large conidia are produced in clusters or individually, and they are sickle-shaped, curved, with a rounded base and three septa. Their size ranges from 19–45 × 2.5–5 μm, while five-septate conidia measure 30–60 × 3.5–5 μm. Small conidia are typically one to two cells, oval or kidney-shaped, measuring 5–26 × 2–4.5 μm. These small conidia are scattered throughout the mycelium and are generally not mixed with the larger ones. Chlamydospores are spherical, smooth or wrinkled, mostly single-celled, and can be found at the tips or along the hyphae, with sizes ranging from 5–15 μm. This fungus can also infect tomatoes, onions, garlic, melons, and straw, among other crops.
The pathogen overwinters in the soil or on infected potato debris in the form of mycelium or chlamydospores. During the growing season, conidia produced on infected plants are spread by rain or irrigation water and enter through wounds. High humidity, temperatures above 28°C, and low-lying fields with poor drainage create ideal conditions for disease development.
To manage the disease, several preventive measures can be taken. First, implement a four-year crop rotation with grasses or green manure crops to reduce pathogen buildup in the soil. Second, select healthy sweet potato seedlings, apply well-decomposed organic fertilizers, and maintain proper water and nutrient management to lower disease incidence. If necessary, apply a 12.5% carbendazim solution diluted 300 times, which can help control the infection effectively when used appropriately.
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