Cucumber chalk disease prevention and control measures

Cucumber chalk disease primarily affects the base of the stem or the fruit near the ground. The infected area turns dark brown and is covered with white, fluffy mycelium that spreads radially with clear boundaries. In later stages, numerous small, brown sclerotia resembling radish seeds develop. When humidity is high, the fungal hyphae spread to the root area or the surface of nearby fruits, leading to the formation of more sclerotia. As the base of the plant rots, the stems and leaves begin to wilt or die. Prompt application of **pesticides** is essential for effective control. The disease thrives under specific environmental conditions, with an optimal temperature of 30°C and relative humidity above 95%. High temperatures and humidity greatly favor the development and spread of the disease. In the spring of 2000, the city experienced unusually warm weather, with average temperatures from early March to mid-April reaching 12.4–13.4°C—2.1–3.1°C higher than normal. Greenhouse temperatures often reached 28–30°C. These conditions, combined with excessive watering, created a perfect environment for the outbreak of chalk disease. Several factors contribute to the prevalence of the disease. Poor land preparation, improper planting density, lack of proper management, overwatering, poor ventilation, insufficient organic fertilizer, low-lying terrain with poor drainage, and failure to remove infected plants in time all play a role. Greenhouses are particularly vulnerable due to these unfavorable conditions. To manage the disease effectively, the following measures can be taken: 1. Apply 100–150 kg of slaked lime per acre to adjust soil pH to neutral, or add large amounts of fully decomposed organic fertilizer. 2. Immediately remove and destroy any infected plants to prevent further spread. 3. At the early stage of infection, apply 40% pentachloronitrobenzene or 15% triadimefon (Pulverine) wettable powder. Alternatively, mix 1 part of 50% methyl chlorpyrifos (Liques) WP with 100–200 parts of fine soil and sprinkle it around the roots of affected areas. This treatment has proven highly effective. If needed, spray 20% methyl chlorophosphorus emulsifiable concentrate diluted 1000 times every 7–10 days, applying it once or twice as a preventive measure. 4. Utilize *Trichoderma* species for biological control. Mix 0.4–0.45 kg of *Trichoderma harzianum* Rifai with 50 kg of fine soil and apply it to the base of infected plants at a rate of 1 kg per mu. This method can significantly reduce disease progression. By combining cultural, chemical, and biological control methods, the occurrence and impact of cucumber chalk disease can be effectively managed. Regular monitoring and timely intervention are crucial to maintaining healthy crops and minimizing economic losses.

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