Chrysanthemums are commonly affected by three major diseases: rust, gray mold, and black spot. These diseases often occur together, which can significantly impact the plant's flowering and reduce its ornamental value. Over the past few years, our research has focused on understanding these diseases and developing effective prevention and treatment strategies.
**1. Rust**
Rust primarily affects the leaves and stems of chrysanthemums, with the leaves being the most vulnerable part. In the early stages, small yellow spots appear on the leaves, which later turn brown and slightly raised—these are uredia spores. As the disease progresses, they release a yellow-brown powder known as summer spores. In later stages, dark brown or black oval-shaped swellings develop on the leaves, sometimes on the petioles and leaf stems. These are winter teliospores. Severe infections can lead to the death of entire leaves. Factors such as poor cultivation practices, inadequate ventilation, poor drainage in low-lying areas, nutrient deficiencies (especially nitrogen), and high humidity contribute to the development of rust.
**Control Methods:**
- **Improve Cultivation Practices:** Ensure proper drainage, especially in high-humidity soils. Keep pots free of clogged drainage holes. Apply balanced fertilizers with an emphasis on phosphorus and potassium to enhance plant resistance.
- **Remove Infected Parts:** Immediately cut off and dispose of infected leaves and branches. Burning or burying them helps eliminate pathogens.
- **Chemical Control:** Apply 65% zinc oxide at a 500x dilution once symptoms appear. Alternatively, use a 0.3–0.5° Baume sulfur solution. For long-term control, spray lime sulfur at 4–5° before spring growth begins, repeating this for several years.
**2. Gray Mold**
Gray mold mainly affects the leaves, stems, and flowers of chrysanthemums. Infected leaves show brown, rim-like wrinkles along the edges, while the petioles and pedicels become soft and eventually rot. When flowers are affected, seed production is impacted. High humidity, excessive nitrogen fertilizer, overcrowded planting, and heavy soil conditions all favor the development of gray mold.
**Control Methods:**
- **Use Disease-Free Soil:** The pathogen survives in the soil during winter. Always use clean, new soil for both garden and potted plants.
- **Remove Diseased Plants:** Promptly remove and destroy infected parts by burning or deep burial to prevent spread.
- **Preventive Treatment:** Soak newly planted chrysanthemums in a 65% zymogen zinc solution diluted 300 times for 10–15 minutes before planting.
- **Improve Air Circulation:** Enhance ventilation and light exposure. Avoid overuse of nitrogen fertilizer. During rainy seasons, ensure proper drainage and avoid watering directly on the soil. Early-stage treatments include applying a 0.3–0.5° Baume sulfur solution or fungicides like zineb or carbendazim.
**3. Black Spot**
Black spot disease mainly targets the leaves of chrysanthemums. Initially, small black spots appear and gradually grow larger. The edges turn dark brown, while the center becomes grayish-black. In severe cases, multiple lesions merge, causing the leaves to turn completely black and fall off. This disease is more common after heavy rains.
**Control Methods:**
- **Drain Excess Water:** Ensure proper drainage during the rainy season to reduce soil moisture.
- **Prune Regularly:** Remove old, lower parts of the plant to improve air circulation and reduce humidity between plants.
- **Remove Infected Leaves:** Immediately remove any diseased leaves and spray the plants thoroughly with a 0.3–0.5° lime sulfur solution.
By following these preventive and control measures, gardeners can effectively manage these common chrysanthemum diseases, ensuring healthier and more vibrant blooms throughout the growing season.
Hydrogen Water Machine,Hydrogen Water Generator,Best Hydrogen Water Machine,Molecular Hydrogen Water Machine,Hydrogen Water Maker
Shenzhen Yibainian Investment Industrial Co., Ltd. , https://www.100hydrogenwater.com