Phlebitis, commonly known as Phytophthora, is one of the most destructive diseases affecting the production of squash. Proper prevention and control measures are essential to ensure high yields and maximize income. This disease is a serious soil-borne infection caused by species such as *Phytophthora capsici* and *P. bergii*. It can affect the entire growth cycle of the plant, targeting roots, stems, and leaves. The disease typically appears in July and August during hot and rainy periods or after irrigation. Symptoms begin with water-soaked lesions on the surface of the soil, which then develop into dark green spots that gradually turn yellowish-brown and rot. The roots may become soft and shriveled, leading to wilting and eventual plant death.
In the early stages, the stems show water-stained spots that expand over time, becoming sunken and gray-brown. When vines are infected, the damage often occurs near the tips, starting with dark green, waterlogged depressions. As the disease progresses, the upper parts of the plant wilt and collapse. On the leaves, large round or irregular water spots appear, eventually turning brown and causing the leaf to wither and fall off. Fruits show initial dark green water spots that enlarge, leading to complete rot. In humid conditions, a white or gray mold develops, accompanied by an unpleasant odor.
The primary source of infection is oospores present in the soil and plant debris. These spores survive winter and spread through wind, rain, or irrigation. The disease thrives in temperatures between 10–37°C, with the ideal range being 28–30°C and soil moisture above 85%. Heavy rainfall followed by sudden dry weather increases the risk of outbreaks. Water from canals tends to carry more pathogens than well water. Flood irrigation or prolonged watering (over 4–6 hours) can lead to rapid infection, with symptoms appearing within 2–3 days. Clay soils are more prone to infection compared to sandy or loamy soils. Continuous planting of cucurbits without crop rotation worsens the problem. Mulched fields have lower incidence compared to open fields, and raised bed cultivation is more effective than flatbeds. Drip irrigation is better than flood or furrow irrigation. Overwatering, especially at noon, increases the risk. Excessive tillage and undecomposed organic manure also contribute to disease development.
To manage Phytophthora effectively, a comprehensive approach is needed. First, implement a rational crop rotation system, avoiding consecutive planting of melons. Rotate with non-cucurbit crops like wheat, corn, or legumes for at least four years. Choose well-drained, fertile soils with good structure and drainage. Second, use high-quality seeds with high purity, germination, and low moisture content, such as varieties like New Seed Melon No. 1 or Min Melon No. 1. Treat seeds with a 2.5% Clarion solution before sowing. Third, adopt drip irrigation under mulch or deep ridge cultivation to improve water efficiency and reduce disease risk. Fourth, apply scientific irrigation practices, avoiding overwatering and ensuring proper drainage. Finally, use fungicides like 64% Oxycarboxin WP, 58% Metalaxyl WP, or 72% Ridomil Gold WP as a preventive measure. Spray immediately after heavy rains and repeat every 5–7 days. Combining foliar fertilizers with fungicides can help reduce costs while improving plant health.
Author: Emin 164 groups
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