Methods for Preventing and Controlling Southern Blight in Clivia and Points to Note

Symptoms

The rhizome near the ground surface shows water-soaked yellow-brown to reddish-brown wet rot, the leaves can be pulled away very easily, and the diseased part develops a distinct white mycelial layer and rapeseed-like sclerotia; the plant wilts and dies.

Conditions for Disease Onset

Plants grown in soil carrying the pathogen are prone to the disease in hot, rainy and humid summers. Under humid and hot greenhouse conditions, the disease can occur earlier.

Pathogen

Sclerotium rolfsii Sacc. belongs to the subdivision Deuteromycotina, order Mycelia Sterilia, genus Sclerotium, species Sclerotium rolfsii. The hyphae are white with a silky luster, spreading in a feather-like radial pattern over the substrate, and are septate; the sclerotia are spherical or elliptical, 0.5-1.0 mm in diameter, and up to 3 mm for the large ones, smooth and glossy, initially white and later turning brown.

Transmission Route

The pathogen mainly overwinters in the soil as sclerotia, and can also survive as mycelium on diseased plant residues. The sclerotia directly produce hyphae that spread through soil cracks and pores to cause damage.

Prevention and control methods:

1. Chemical control:

1. 50% Dexon wettable powder at 1000 times dilution.

2. 50% Folpan wettable powder at 3000 times dilution.

3. 75% Mepronil wettable powder at 1000 times dilution (the solution should be sprayed onto the growing medium, and watering should be stopped for 5-7 days after spraying).

2. After southern blight is found, the diseased leaves, diseased plants and nearby growing material should be removed and burned, and nearby plants should immediately be sprayed with control chemicals more than three times.

3. Before planting, the medium should be sterilized with steam, or drenched with 0.6% urea and then covered for one week for disinfection.