High temperature, high humidity, vegetable disease prevention

In the summer of this year, our province has experienced an increase in hot and rainy weather. This unusual climate has led to poor vegetable growth and a higher risk of pest and disease infestations. The combination of high temperature and humidity creates ideal conditions for root rot, leggy growth, and other undesirable phenomena. It also promotes the spread of pests and diseases, which can lead to plant death and reduced yields. High humidity is particularly problematic for vegetables. Under such conditions, plants are often waterlogged, making them more prone to legginess—especially eggplants and melons. Prolonged exposure to moisture weakens cell walls, reducing the resilience of plant tissues. This makes them more susceptible to heat stress, resulting in sunburn and damage that affects both growth and yield. Additionally, saturated soil leads to low oxygen levels around the roots, increasing the risk of root infections and soil-borne diseases, which can cause entire plants to die, commonly referred to as "dead trees." High temperatures also pose serious challenges. Continuous heat and rain during the autumn seedling stage can hinder normal growth, causing wilting, stunted development, and issues with flower bud formation. This often results in early flowering, fruit drop, and malformed fruits, significantly lowering the economic returns for farmers. In Shouguang City, where most vegetables are currently in the nursery stage, damping-off and blight are common, especially in eggplants and melons. Damping-off is characterized by a water-soaked base at the seedling’s stem, which eventually collapses. Bacterial infections typically appear once true leaves emerge, with symptoms like daytime wilting and stem contraction. The prevalence of these diseases is currently high, along with other issues like sclerotinia, gray mold, and downy mildew. To manage these problems, several control methods are recommended. Agricultural practices include improving drainage, keeping fields clean, using sunny mornings, and enhancing greenhouse ventilation. Chemical treatments involve smoke fumigation when humidity is high—such as using 20% smoked spirit or 20% fast-smoked tablets in a 200-square-meter greenhouse. In clear weather, spraying with 58% metalaxyl or 68% gold mine at 600 times dilution helps prevent dampness and downy mildew. For damping-off and other fungal diseases, 50% procymidone at 1500 times or thiophanate-methyl at 1000 times is effective. For solanaceous vegetables, careful watering is essential to avoid over-saturation. Water should be applied only when necessary, and the focus should be on maintaining dry conditions to prevent disease. After planting, products like Hymexazol (2000x) or Root Cork (600x) can be used for root treatment. During harvest, applying Jian Jian Bao at 40–60 kg per acre helps prevent disease. For melons, controlling growth and maximizing production is key. Temperature and irrigation must be carefully managed to avoid excessive growth under high-temperature and high-humidity conditions. Nighttime temperature control and increased ventilation help improve nutrient transport. Potash fertilizers should be applied appropriately to boost yield. For powdery mildew, early intervention with 10% World High Water Dispersant (1000–1500x) or 40% DuPont Fuxing (5000x) is recommended. Alternatively, heating greenhouses to 42–45°C for two hours at noon can effectively kill pathogens. Leafy vegetables grown outdoors require attention to drainage during heavy rainfall to prevent waterlogging. Diseases like cruciferous soft rot can be controlled with 72% agricultural streptomycin (4000x), neophytin (4000x), or 77% copper oxychloride (600–800x). Timely harvesting is crucial to avoid rain damage and maintain market value. For pest control, specific measures are recommended: 1. Melon locusts: 0.6% Excision Ling at 1250–1500x. 2. Yellow song jumpers: 90% trichlorfon (800x) spray, repeated 2–3 times. 3. Diamondback moth: 5% Rui Jin (1000–1500x) or 5% Suppository EC (2000x). 4. Starscream: 20% wolfberry (3000x) plus 1% insect worm light (3000x). By implementing these strategies, farmers can better protect their crops and ensure healthier, more productive harvests despite the challenging weather conditions.

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