What pathogen causes sclerotium disease?

The sclerotium disease pathogen of Chinese orchids mainly harms the bracts of the orchid plant. The function of the bracts is mainly to protect the growing point of the meristem. If the bracts are harmed by sclerotium disease, the growing point is generally more prone to necrosis, affecting the chance of lateral bud germination. In the early stage of the sclerotium disease pathogen harming the bracts, irregular brown lesions appear at the very tip or along the leaf edge, gradually turning gray, and the tissue dies. On the dried bracts, numerous round black sclerotia of varying sizes form, and when the sclerotia mature they form sclerotial bodies and fall into the medium; when conditions are suitable, the sclerotia will infect other healthy bracts again. Control methods: (1) If an orchid plant is found to be infected with sclerotium disease, the diseased bracts should be cut off, and the diseased cut leaves should be burned immediately; replace the sphagnum moss and medium to block the spread of the pathogen. (2) When supplying water, try to prevent water from accumulating inside the bracts. (3) During periods of root development and new shoot growth, the bracts are more easily injured, and the pathogen easily invades and infects through these wounds, so chemical control should be applied more often. (4) Maintain a good ventilation environment, and do not place plants too densely together. (5) Avoid human-caused or mechanical injury. (6) Choose a medium with good aeration, free of contaminating microorganisms, and fully piled and fermented,cultivationmedium, such as Lanbaole,orchidfour-in-one special organic planting material, etc. After division and repotting, immediately apply 75% thiophanate-methyl wettable powder at a dilution of one thousand times, adding a spreader-sticker at one thousand five hundred times. Spray the bracts, stem base, and drench the medium. Place in a cooler spot, and do not water by drenching within two days. (7) After removing diseased leaves during division, immediately apply chemicals to kill the pathogen. Generally,cultivationmanagers growing Chinese orchids find that their bracts are more susceptible to pathogen infection. The causes of bract rot or withering are none other than: (A) The orchid plant itself carries the sclerotium disease pathogen,cultivationand the manager did not remove it and carry out proper control when planting, so the pathogen infects other healthy bracts again; (b) caused by poor ventilation between plants and in the orchid room; (c) caused by improper watering timing, with water accumulating on the bracts for a long time; (d) during periods of root growth and new shoot growth, the bracts crack and are injured, and the pathogen takes the opportunity to invade through these wounds, while the cultivation manager fails to apply chemical control in time to stop the pathogen from continuing to spread; (e) during planting, the orchid is planted too deep or the sphagnum moss is wrapped too tightly, resulting in poor aeration and poor water accumulation; (f) the cultivation medium has not been fully piled and fermented, and the population density of beneficial microorganisms is too low to suppress the growth of harmful pathogens, giving the sclerotium disease pathogen a large space to survive and reproduce. The presence or absence of bracts is closely related to the overall aesthetic appearance of the orchid plant, its commercial value, and the protection of the growing point. When the bracts necrose, the growing point is relatively prone to necrosis as well, affecting the reproductive yield of Chinese orchids. Therefore, if cultivation managers want to grow Chinese orchids with high yield, good quality, and a good selling price, the first prerequisite is to keep the bracts robust. Normally, it is most necessary to regularly use chemicals to suppress the proliferation of the pathogen, remove the causes of bract infection, and apply the microbial additive Mandian 18 to antagonize the growth of the genus causing sclerotium disease.