Symptoms and control methods of tulip southern blight

Symptoms: The whole plant wilts, with white mycelial strands or rapeseed-like tan-brown small sclerotia wrapped around the stem base, and the affected parts turn brown, rot and decay. Large amounts of white mycelial strands and tan-brown fungal bodies are visible on the soil surface.

Pathogen: Sclerotium rolfsii Sacc., called southern blight, belongs to the Deuteromycotina fungi. The hyphae are white and silky, spreading in a fan-like or radial pattern, then gathering into mycelial strands or tangling into sclerotia. The sclerotia resemble rapeseeds, initially white to yellowish-white, later turning tan-brown, round, with a smooth surface. In addition, it has been reported that Corticium rolfsii (Secc.) Curzi. is also a pathogen of this disease.

Transmission routes:

① The pathogen overwinters in the soil as sclerotia or mycelial strands remaining in diseased plant debris. When conditions are suitable the following year, the sclerotia or mycelial strands produce hyphae for primary infection.

② The silky hyphae produced by diseased plants extend to contact neighboring plants, or the sclerotia spread through water flow for secondary infection, causing the disease to spread and expand. The disease is severe in continuous cropping, or with heavy clay soil, low-lying terrain, or in years or seasons with high temperature and high humidity.

Control methods: When diseased plants are found, pull them out promptly and burn them. Drench the planting holes and neighboring plants with a 1000-1600 times dilution of 5% validamycin aqueous solution, or a 500-600 times dilution of 50% Tian'an aqueous solution, or a 1000 times dilution of 20% tolclofos-methyl emulsifiable concentrate, or a 500 times dilution of 90% fenaminosulf wettable powder, drenching 0.4-0.5 liters per plant (hole). In conjunction with plowing, mix in 100-150 kg of lime powder per mu to make the soil slightly alkaline, which can inhibit the reproduction of the southern blight pathogen.