What to Do If a Peony Gets Southern Blight? A Detailed Guide to Prevention and Control
Southern blight of peony mainly occurs at the stem base of seedlings near the ground. Soil and fertilizer are the sources of infection, and the disease is especially severe when sweet potato or soybean was the previous crop. It is more likely to occur around flowering and during hot, rainy seasons. In the early stage, there are no obvious symptoms on the aboveground parts; as temperature and humidity rise, mycelium spreads from the rhizome out onto the soil surface, densely covering the area around the rhizome in a cloud-like form, and finally forming brown, millet-grain-like sclerotia. The top shoots of diseased plants wither, the leaves wilt and droop, and eventually the whole plant dies.
Prevention and control methods:
1. Choose rotation with gramineous crops; it is not suitable to rotate with root and rhizome medicinal herbs, sweet potato, peanut, broad bean, and other such crops.
2. Select disease-free seedlings and disinfect healthy seedlings. For disinfection, use a 50% thiram or 70% thiophanate-methyl or carbendazim 800-1000 times solution and soak for 10-30 minutes.
3. To prevent disease at the seedling stage, treat the soil with 70% quintozene powder, using 2.5 kg per mu, adding 50 kg of dry fine soil, mixing evenly, and spreading it in the sowing or cutting furrows before sowing or cutting. After planting, spray with Xin Gao Zhi Mo to isolate pests and diseases and protect the healthy growth of the plants.
4. When diseased plants are found, dig them out promptly with the soil and burn them, and disinfect the diseased holes with lime.
5. In the early stage of disease, spread 70% quintozene powder at 2.5 kg per mu in the nursery, then loosen the soil after application so that the powder mixes evenly into the soil; alternatively, irrigate the seedling roots with a 50% carbendazim wettable powder 500 times solution or 1% copper sulfate solution.
How to Prevent and Control Peony Southern Blight
Southern blight of peony mainly occurs at the stem base of seedlings near the ground. Soil and fertilizer are the sources of infection, and the disease is especially severe when sweet potato or soybean was the previous crop. It is more likely to occur around flowering and during hot, rainy seasons. In the early stage, there are no obvious symptoms on the aboveground parts; as temperature and humidity rise, mycelium spreads from the rhizome out onto the soil surface, densely covering the area around the rhizome in a cloud-like form, and finally forming brown, millet-grain-like sclerotia. The top shoots of diseased plants wither, the leaves wilt and droop, and eventually the whole plant dies.
Prevention and control methods:
1. Choose rotation with gramineous crops; it is not suitable to rotate with root and rhizome medicinal herbs, sweet potato, peanut, broad bean, and other such crops.
2. Select disease-free seedlings and disinfect healthy seedlings. For disinfection, use a 50% thiram or 70% thiophanate-methyl or carbendazim 800-**** times solution and soak for 10-30 minutes.
3. To prevent disease at the seedling stage, treat the soil with 70% quintozene powder, using 2.5 kg per mu, adding 50 kg of dry fine soil, mixing evenly, and spreading it in the sowing or cutting furrows before sowing or cutting. After planting, spray with Xin Gao Zhi Mo to isolate pests and diseases and protect the healthy growth of the plants.
4. When diseased plants are found, dig them out promptly with the soil and burn them, and disinfect the diseased holes with lime.
5. In the early stage of disease, spread 70% quintozene powder at 2.5 kg per mu in the nursery, then loosen the soil after application so that the powder mixes evenly into the soil; alternatively, irrigate the seedling roots with a 50% carbendazim wettable powder 500 times solution or 1% copper sulfate solution.
How to Prevent and Control Peony Southern Blight
Symptoms:The symptoms of various susceptible plants are broadly similar. The disease mainly occurs at the stem base of seedlings near the ground. When it first appears, the epidermal layer of the diseased part turns brown and gradually spreads outward, and white silky mycelium is produced on the diseased part. The mycelium fans out and spreads to the nearby soil surface, after which rapeseed-like tea-brown sclerotia form on the surface of the seedling base or on the mycelial layer on the soil surface. After the seedlings become diseased, the stem base and root cortex rot, the transport of water and nutrients in the plant is cut off, the leaves turn yellow and wilt, and the whole plant dies.
Pathogen;Sclerotium rolfsii Sacc. (Sclerotium rolfsii). Sclerotium rolfsii belongs to the Deuteromycotina, Hyphomycetes, Mycelia Sterilia. This fungus does not produce asexual spores and rarely produces sexual spores. The mycelium is initially white and later slightly brownish, 3-9 micrometers in diameter; in the later stage, the mycelium can densely cluster together to form rapeseed-like sclerotia.
Transmission routes;The pathogen generally overwinters as mature sclerotia in the soil, on infected weeds, or on diseased plant residues. It spreads through rainwater. Sclerotia can survive in the soil for 4-5 years. Under suitable temperature and humidity conditions, the sclerotia germinate and produce mycelium that invades the plant body. In the Yangtze River basin, the disease generally begins to occur in early June, with July-August being the peak period of the disease, and it basically stops occurring after September. Under conditions of 18-28°C and high humidity, it takes only 8-9 days from sclerotial germination to the formation of new sclerotia, and about 9 days from sclerotial formation to maturity.
Disease conditions:The pathogen prefers high temperature and high humidity. The optimum temperature for growth is 30-35°C, and development stops above 40°C. Soil pH 5-7 is suitable for disease occurrence, and the disease occurs very little in alkaline soil. In garden plots with rich soil humus, high nitrogen content, heavy clay soil, and relatively acidic conditions, the disease incidence is high.
Prevention and control methods:
1. To prevent disease at the seedling stage, treat the soil with 70% quintozene powder, using 250 g per 67 sq m, adding 5 kg of dry fine soil, mixing evenly, and spreading it in the sowing or cutting furrows before sowing or cutting.
2. In the early stage of disease, 70% quintozene powder can be spread on the soil surface in the nursery, also using 250 g per 67 sq m; after application, loosen the soil so that the powder mixes evenly into the soil. Alternatively, irrigate the seedling roots with Bi Jun Sha 800-**** times solution, 50% carbendazim wettable powder 500-800 times solution, or 50% thiophanate wettable powder 500 times solution, or 1% copper sulfate solution, or carboxin 10 ppm, or oxycarboxin 25 ppm, which can control the spread of the disease.
3. In spring and autumn, remove soil and expose the roots. After symptoms appear on the aboveground parts of the tree, remove the soil near the main root at the base of the trunk and expose it to the sun, which can inhibit the development of the disease. Root exposure can be carried out from early spring in March until leaf fall in autumn. Before the rainy season arrives, the tree hole can be filled level to prevent adverse effects. When exposing the roots, also note that soil ridges should be built around the hole to prevent water from flowing in.
4. Select disease-free seedlings. When transporting seedlings, inspect them strictly, remove diseased seedlings, and disinfect healthy seedlings. For disinfection, use Miao Jun Ling 200-300 times solution, 70% thiophanate-methyl or carbendazim 800-1000 times solution, 2% lime water, or 0.5% copper sulfate solution and soak for 10-30 minutes, then plant. They can also be soaked in 45°C warm water for 20-30 minutes to kill root pathogens.
5. Treatment of diseased trees. After determining that the roots are diseased based on symptoms on the aboveground parts of the tree, dig away the soil at the base of the trunk to find the affected area. After confirming it is southern blight, use a knife to thoroughly scrape off the lesions on the root crown, disinfect the wound with antibacterial agent 401 at 50 times solution or 1% sulfuric acid solution, then apply a protective agent such as Bordeaux mixture externally, and cover with new soil.
6. Dig isolation ditches. Around diseased plants, dig isolation ditches to block off the diseased area.