Occurrence, epidemic patterns and damage characteristics of sitting-chang disease

The optimum growth temperature for Fusarium is 20°C-30°C. At this temperature it can produce large numbers of conidia for primary and secondary infection, while under unsuitable conditions it forms chlamydospores that can survive in the soil for many years. Fusarium is a typical soil-inhabiting fungus, so the parts of the host plant it infects and parasitizes are mainly the underground rhizome area. When we buy a whole pottedorchidwith pathogen-contaminated potting soil, the pathogen is brought into the orchid nursery. When the plants are divided, the pathogen attached to the soil enters the orchid plants through the cut surfaces of the pseudobulb heads and root wounds, and lies dormant there. From April to June, warm and humid weather promotes its growth, and it spreads with rainwater or splashing from watering. In Guangdong, it first appears in early April, begins to break out in late May, peaks in early June, and as the high-temperature weather of July arrives, its spread is somewhat inhibited. Excerpted from "OrchidBible" Shunde Guolan Association Hu Yingdong