Orchid southern blight is a disease caused by fungi

OrchidSouthern blight (Orchid southern blight) is also calledOrchidbasal rot (Orchid basal rot) Distribution range: worldwide; common in southern China. Pathogen: Sclerotium rolfsii. Hosts: Cattleya, Cymbidium, Oncidium, Phalaenopsis, Spathoglottis, Vanda, etc. Symptoms: The earliest sign of infection is yellow to light brown water-soaked lesions appearing at the base of the stem. The pathogen mainly damages the base of the plant and infects young leaves and roots. Affected leaves turn yellow, wilt, and die. Subsequently, rapid decline and rot of the roots and pseudobulbs occur. If it spreads upward, ring-shaped cankers appear on the stem, followed by rot, leading to the death of the entire plant. The network of mycelium is first white, then becomes brown or black small round bodies called sclerotia, about 2-4 mm in diameter. They can survive for many years in the soil, on benches, or on flower stands. Control: Once this disease signal appears, immediately cut off the diseased stems and soak the whole plant oforchidin a 1% copper sulfate bath solution (i.e. 10 g copper sulfate mixed with 1 L water) for disinfection. Contaminated flower pots, potting soil, flower stands, etc. can be disinfected by spraying with a 50% zineb 500-1000 times dilution. Using 50% carbendazim wettable powder (5-10 g/sq m) mixed with fine soil and incorporated into the soil, or spraying the rhizosphere soil with a 1000 times dilution, can also control the spread of the disease. Note: This disease is relatively common in the south, and infected Chinese orchids are occasionally found. It is reported that a basal rot quite similar to southern blight has been found in Shanghai, harmingCymbidium ensifolium. On diseased plants, light brown water-soaked spots first appear at the leaf base, then spread to the entire leaf, eventually rotting and causing death. However, the pathogen is not yet clear, and the control methods are the same as above. (Chen Xinqi, Ji Zhanhe)