With the expansion of greenhouse cucumber cultivation, plant diseases have become a major challenge affecting both yield and quality. Common diseases include downy mildew, gray mold, powdery mildew, fusarium wilt, and anthracnose. Below are detailed descriptions and control measures for these prevalent issues.
**1. Cucumber Downy Mildew**
**Symptoms:**
This disease affects both seedlings and mature plants, primarily targeting the leaves. Early symptoms appear as water-soaked lesions on the leaf margins or back, especially noticeable in the morning. These lesions gradually expand, confined by leaf veins, forming irregular brown or yellowish-brown spots. High humidity leads to the development of a gray-black mold layer on the leaf surface. As the disease progresses, the lesions rupture, causing leaf curling and drying.
**Control Measures:**
- **Chemical Control:** Apply 75% chlorothalonil WP diluted at 600 times, 70% EDPA-MnZn WP at 500 times, or 72.2% Propineb 800 times. Spray every 7–10 days, ensuring thorough coverage on both leaf surfaces.
- **Cultural Control:**
- **Temperature Management:** In the morning, ventilate for 30 minutes before sealing the greenhouse. Raise the temperature to 28°C or higher, then introduce a light breeze when it reaches 30°C. Maintain temperatures between 28–32°C in the morning, and lower them to 20–25°C in the afternoon. At night, keep the temperature around 18–20°C, with a minimum of 14°C.
- **High-Temperature Fumigation:** On sunny days in April, close the greenhouse and raise the temperature to 45°C for 2 hours to kill pathogens. Repeat this weekly as a preventive measure. Use non-dripping films and ensure proper watering and nutrition to strengthen plants.
**2. Gray Mold**
**Symptoms:**
Gray mold affects flowers, fruits, stems, and leaves. Infected flower pedicels become water-soaked and discolored, leading to soft rot and the appearance of brown mold. Affected fruits may rot, and infected flowers can fall onto leaves, creating large dead spots. Stems and leaves may also show water-soaked lesions with a gray-brown mold layer.
**Control Measures:**
- **Chemical Control:** Apply 50% carbendazim WP at 1500 times, 50% iprodione WP at 2000 times, or 28% gray mold WP at 500 times. Spray every 6–7 days for 3–4 applications, using about 60 liters per 667 square meters.
- **Cultural Control:** Monitor temperature and humidity, remove diseased parts promptly, and dispose of infected materials outside the greenhouse.
**3. Powdery Mildew**
**Control Measures:**
Spray 40% Fungin EC at 8000–10000 times, 25% Triadimefon at 1500 times, or 50% carbendazim WP at 600–800 times. Alternate between these agents every 7–10 days for 2–3 treatments.
**4. Fusarium Wilt**
**Control Measures:**
Apply 50% carbendazim WP at 500 times, 70% thiophanate-methyl WP at 800 times, or 70% dextromethorphan WP at 1000 times. Water the roots with 250 ml per plant, repeating every 7 days for up to three applications.
**Additional Prevention Strategies:**
Select resistant varieties, treat seeds before planting, practice crop rotation, use grafting techniques, improve cultural practices, and maintain cleanliness in the growing area.
**5. Anthracnose**
**Control Measures:**
Use 70% mancozeb at 400 mg/L, 200 times agricultural anti-120, 2% Wuyimycin (BO-10) at 200 times, 70% thiophanate-methyl WP at 800 times, or 75% Streptomyces 500 times. Ensure even spraying on both sides of the leaves.
By implementing these integrated management strategies, growers can effectively reduce the impact of common cucumber diseases and improve overall crop health and productivity.
Lemon Tea
DIYAS development Limited , https://www.diyastea.com