Comprehensive Control of Orchid Diseases

White silk disease, caused by fungi, is one of the main diseases of orchids, second only to anthracnose. Once this disease occurs, the harm and loss will be far more than anthrax!

1. The pathogen: orchid white silk fungus is caused by sclerotium rolfsii, its sclerotia is small, it is formed by white silk-like mycelium, at first it is milky white, gradually turns beige, and finally becomes dark brown, similar to the size of rapeseed. The optimum temperature for growth is 25-35 degrees, and stop growing when it is below 10 degrees or higher than 40 degrees. If you exceed 100 degrees, you will die.

two。 Symptoms of the disease: the damaged orchid plant appeared brown and rotted at the base of the stem and fleshy root close to the basin surface, and soon appeared on the surface of white silk, which radiated and continued to spread to the surface of the basin soil around the root. in the later stage, many particles (sclerotia) shaped like rapeseed were formed on the white filaments, and the sclerotia was white at first and gradually turned dark brown.

3. The incubation period of white silk disease is very short and can occur within 1 week after invasion. Acid soil is beneficial to the occurrence of the disease, and the disease is more likely to occur in the environment of high temperature and humidity. Therefore, it is easy to cause this disease in the high temperature and rainy season. The damage of white silk disease was mainly caused by the buds and seedlings of orchids, and the hyphae began at the base of the leaf sheath and gradually extended to the base of the central leaves of the seedlings, until the young bulbs and tender roots were disintegrated, the yellow liquid exuded and rotted, and finally led to the lodging of the orchid leaves and the death of the whole seedling. If a vaccine is not treated in time after infection, the plants in the same basin will not be spared.

4. Preventive measures:

(1)。 Create an environment suitable for orchid growth: the incidence of white silk disease of orchids is related to the high humidity of the environment. Potted orchids should avoid direct rain for a long time, especially in the plum rain season from May to June and the hot August to September. Therefore, orchids had better be cultivated in sheds, with rain shelter and sunshade facilities to create ventilation. a transparent environment.

(2)。 Choose clean plant materials to plant: orchid white silk disease is a soil-borne disease, mycelium can also die in the hot sun. Therefore, the cultivated soil should be disinfected at high temperature and the immature plant residues should be screened out. The use of small powder substrates should be avoided when planting.

(3)。 Artificial control: keep the surface of the basin soil a little drier, which is beneficial to inhibit sclerotia germination. Orchid pots should not be too dense. Organic fertilizers must be fully fermented and rotten. Remove weeds on the surface of orchid pots in time (weeds are also host plants of white silk disease). Reduce the infection source of bacteria.

5. Chemical control: in the disease-prone season, the 1000-fold solution of 70% methyl thiophanate wettable powder or 75% chlorothalonil wettable powder can be sprayed to the basin or the base of leaves, once every other week for 2 to 3 consecutive times. The other 25% carbendazim 1000 times solution and 50% thiram wettable powder solution also had a good effect on the control of orchid white silk disease. Once it is found that the plants are infected by white silk disease, the seriously damaged plants should be removed and burned and sprayed with 800 times of thiram or chlorothalonil to prevent further infection. When spraying, focus on the base of the stem of the orchid, combined with watering the root will be better. Watering should be reduced during this period. At the same time, check every day, if the disease continues to occur, you should turn the basin, remove all rotten roots and soak the whole orchid in 800 times chlorothalonil for half an hour. Then put on new plant materials and plant to small pot isolation, and stop fertilization, mainly to clean-up.

To sum up, the prevention and control of white silk disease of orchids should be as follows: prevention, rain protection, selection of clean plant materials and strengthening ventilation. Light transmission, medication prevention during the onset of the disease, early removal of diseased plants and isolated planting. (Xinyuanxuan)