**Prevention and Treatment of Ginseng Fruit Black Spot Disease**
**Symptoms**
The disease primarily affects the leaves of ginseng plants. Initially, small black spots appear on the leaf surfaces, which gradually expand into nearly circular or irregular shapes. As the infection progresses, these lesions often merge into larger patches, leading to leaf drying or death.
**Morphological Characteristics of the Pathogen**
The pathogen is an *Alternaria* species, a type of fungus. The mycelium is filamentous with septa. Conidiophores emerge from the stomata in clusters, typically 1–5 per cluster. These stalks are cylindrical or short rod-shaped, dark brown in color, and contain 1–4 septa. Their size ranges from 30.6–104 μm in length and 4.3–9.19 μm in width. The conidia are long, oval, or inverted stick-like, pale yellow, measuring 85.6–146.5 μm in length and 11.7–22 μm in width. They have 1–9 septa, spaced 7–13 apart, with a long, clear apex. Most conidia contain 1–3 septa, with dimensions of 6.3–74 × 3–7.4 μm. The pathogen can grow between 1–45°C, with optimal growth at 26–28°C. Conidia germinate in water within 1–2 hours at 6–24°C, while at 28–30°C, germination occurs in just 35–45 minutes. Each spore can produce 5–10 germ tubes.
**Disease Characteristics**
The pathogen overwinters on infected plant debris, seeds, and diseased tissues. It can directly invade through stomata, lenticels, or the epidermis, causing initial infections. Symptoms appear after 2–3 days of incubation, and conidia are produced within 3–4 days. The disease spreads through wind and rain, leading to repeated infestations. When the average temperature remains around 21°C for five consecutive days and relative humidity exceeds 70% for an extended period, the disease becomes active. Rainy seasons significantly influence the spread of the disease, as rainfall affects humidity levels. Additionally, the pathogen is a facultative saprophyte, and poor management practices or replanting ginseng in the same field can lead to insufficient base fertilizer, increasing the risk of infection.
**Control Methods for Ginseng Fruit Black Spot Disease**
1. In protected areas, focus on ecological prevention. Due to large temperature fluctuations during early spring—daytime temperatures of 20–25°C and nighttime temperatures of 12–15°C—the high humidity (over 80%) leads to dew formation, which favors disease development. Adjusting the temperature and humidity inside the greenhouse can help reduce disease spread.
2. At the onset of the disease, apply 5% chlorothalonil powder using the dust method. Use 1 kg per 667 square meters, repeating every 9 days for 3–4 applications.
3. Apply 45% chlorothalonil or 10% quick-acting smoker at a rate of 200–250 g per acre.
4. Follow proper fertilization guidelines by applying sufficient base fertilizer and timely topdressing to enhance the plant’s resistance to disease.
5. Before symptoms appear, spray a 1000-fold solution of 50% phlegm hyacinth powder, a 600-fold solution of 75% Dake Ning (chlorocide) WP, a 600-fold solution of 80% spray WP, or a 500-fold solution of 70% Dyson Mn-Zn wettable powder.
6. Special control agents such as bacterial ampicillin ester may also be used for effective treatment.
By implementing these strategies, ginseng growers can effectively manage and prevent the occurrence of black spot disease, ensuring healthier crops and higher yields.
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