Symptoms and Control Methods of Southern Blight in Hyacinth and Carnation

[Symptoms] The whole plant wilts, with white mycelial strands or rapeseed-like small tea-brown sclerotia winding around the stem base, and the affected parts turn brown and rot. Large numbers of white mycelial strands and tea-brown sclerotia are visible on the soil surface. The disease occurs at the stem base near the soil surface, causing browning and rotting. When the diseased stem tissue is cut open, tea-brown or dark-brown rot develops from the outside toward the center; the xylem also discolors upward, and white mycelium growing in a feathery, radiating pattern can spread to the surrounding soil surface; afterward, on the diseased parts and the mycelium on the surrounding soil surface, sclerotia form that are initially white and later turn yellow-brown and are the size of rapeseeds. After the plant becomes infected, it usually lodges and dies as a whole. On cutting beds, wet rot begins at the callus formation area of the cuttings and can also cause severe crown and root rot.

[Occurrence pattern] The pathogen overwinters in the soil as sclerotia or mycelial strands with diseased residues. When conditions are suitable the following year, the sclerotia or mycelial strands produce hyphae for primary infection. The silky hyphae produced by diseased plants extend and 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 years or seasons with continuous cropping, heavy clay soil, low-lying terrain, or high temperature and high humidity. The pathogen has a wide host range and can damage dozens of plant species, including cactus, orchid, squirrel's tail, cineraria, chrysanthemum, snapdragon, cosmos, dahlia, iris, tulip, hyacinth, lily, and hosta. The pathogen persists as mycelium or sclerotia in diseased residues, diseased plants, wild plants, and soil. Sclerotia can survive in soil for 3 to 4 years, but their survival period in water and wet soil is very short. High humidity favors the spread of the pathogen, and the peak period of disease occurrence is in summer.

[Control methods] 1) Avoid continuous cropping with susceptible plants; the base fertilizer applied should be thoroughly decomposed to prevent the fertilizer from carrying the pathogen; provide proper ventilation and avoid planting too densely. 2) Disinfect the soil before planting, or use 50% Tuzet at 59 per square meter. Remove and burn diseased plants promptly when found, and drench the diseased holes and neighboring plants with 5% Jinggangmycin aqueous solution at 1000-1600 times dilution, or 50% Tian'an aqueous solution at 500-600 times dilution, 20% tolclofos-methyl emulsifiable concentrate at 1000 times dilution, or 90% dexon wettable powder at 500 times dilution. Drench 0.4-0.5 L per plant (hole). When plowing the soil, mix in 100-150 kg of lime powder per 667 sq m to make the soil slightly alkaline, which can inhibit the reproduction of the southern blight pathogen.

Carnation Southern Blight Control Methods

[Distribution]Shanghai, Hangzhou.

[Symptoms]The disease occurs at the stem base near the soil surface, causing browning and rotting; when the diseased stem tissue is cut open, tea-brown or dark-brown rot develops from the outside toward the center; the xylem also discolors upward, and white mycelium growing in a feathery, radiating pattern can spread to the surrounding soil surface; afterward, on the diseased parts and the mycelium on the surrounding soil surface, sclerotia form that are initially white and later turn yellow-brown and are the size of rapeseeds; after the plant becomes infected, it usually lodges and dies as a whole. On cutting beds, wet rot begins at the callus formation area of the cuttings and can also cause severe crown and root rot.

[Pathogen]The pathogen is a fungus, Sclerotium rolfsii; the sclerotia are superficial, 0.5-1.0 mm in diameter, smooth and glossy, and shaped like rapeseeds.

[Occurrence pattern]The pathogen has a wide host range and can damage dozens of plant species, including cactus, orchid, squirrel's tail, cineraria, chrysanthemum, snapdragon, cosmos, dahlia, iris, tulip, hyacinth, lily, and hosta. The pathogen persists as mycelium or sclerotia in diseased residues, diseased plants, wild plants, and soil; sclerotia can survive in soil for 3 to 4 years, but their survival period in water and wet soil is very short. High humidity favors the spread of the pathogen, and the peak period of disease occurrence is in summer.

[Control methods]

(1) Horticultural control: Avoid continuous cropping with susceptible plants; the base fertilizer applied should be thoroughly decomposed to prevent the fertilizer from carrying the pathogen; provide proper ventilation and avoid planting too densely.

(2) Chemical control: Disinfect the soil before planting (see orchid southern blight), or use 50% Tuzet at 5 grams per square meter. If disease occurs during the growing period, dig out diseased plants promptly, disinfect the diseased holes with lime, or drench with 65% zineb at 600-800 times dilution; other fungicides may also be drenched. A 20% emulsifiable concentrate at 1000 times dilution can also be sprayed or drenched to control carnation southern blight.

Carnation Southern Blight

[Distribution] Shanghai, Hangzhou.

[Symptoms] The disease occurs at the stem base near the soil surface, causing browning and rotting; when the diseased stem tissue is cut open, tea-brown or dark-brown rot develops from the outside toward the center; the xylem also discolors upward, and white mycelium growing in a feathery, radiating pattern can spread to the surrounding soil surface; afterward, on the diseased parts and the mycelium on the surrounding soil surface, sclerotia form that are initially white and later turn yellow-brown and are the size of rapeseeds; after the plant becomes infected, it usually lodges and dies as a whole. On cutting beds, wet rot begins at the callus formation area of the cuttings and can also cause severe crown and root rot.

[Pathogen] The pathogen is a fungus, Sclerotium rolfsii; the sclerotia are superficial, 0.5-1.0 mm in diameter, smooth and glossy, and shaped like rapeseeds.

[Occurrence pattern] The pathogen has a wide host range and can damage dozens of plant species, including cactus, orchid, squirrel's tail, cineraria, chrysanthemum, snapdragon, cosmos, dahlia, iris, tulip, hyacinth, lily, and hosta. The pathogen persists as mycelium or sclerotia in diseased residues, diseased plants, wild plants, and soil; sclerotia can survive in soil for 3 to 4 years, but their survival period in water and wet soil is very short. High humidity favors the spread of the pathogen, and the peak period of disease occurrence is in summer.

[Control methods]

(1) Horticultural control: Avoid continuous cropping with susceptible plants; the base fertilizer applied should be thoroughly decomposed to prevent the fertilizer from carrying the pathogen; provide proper ventilation and avoid planting too densely.
(2) Chemical control: Disinfect the soil before planting (see orchid southern blight), or use 50% Tuzet at 5 grams per square meter. If disease occurs during the growing period, dig out diseased plants promptly, disinfect the diseased holes with lime, or drench with 65% zineb at 600-800 times dilution; other fungicides may also be drenched. A 20% emulsifiable concentrate at 1000 times dilution can also be sprayed or drenched to control carnation southern blight