Prevention and Control of White Silk Disease of Orchid

Orchid white silk disease is one of the main diseases of orchids, also known as white silk disease, Sclerotinia sclerotiorum and so on, which is second only to anthrax. Once it occurs, the harm and loss will far exceed anthrax. Usually, the infection begins from April to May, and the disease occurs rapidly during the peak period from June to August, resulting in the rot and death of the injured orchid plants. Let's take a look at the prevention and control methods of orchid white silk disease.

Develop symptoms

White silk disease began from the stem of the orchid plant near the ground, showed yellow to light brown running water disease spots at first, then browned to black brown rot, and spread on the surface of the rhizosphere soil and at the base of the stem, destroying the stem and infecting young leaves and roots, and white hyphae were produced in leaf sheaths and roots. The injured part was waterlogged, decayed and softened, blackened, until the leaves withered, the bacteria spread to the pseudobulb, the sclerotia changed from white to reddish brown to brown necrosis, and in severe cases, the whole plant withered.

Characteristics of the disease

The pathogen of orchid white silk disease is a subphylum fungus, which overwinters with sclerotia in soil or fertilizer and on undecayed remains. In areas with high winter temperature, hyphae can also overwinter on undecayed remains. Sclerotia germinated the following year, spread in the soil and invaded from the base of orchid leaves. Bacteria check has strong resistance to adverse environment and can survive in the soil for several years. It can be spread by running water, irrigation water, Rain Water sputtering and fertilization. The soil is sour and the disease is the most serious, and the disease is easy to be induced in high temperature and humid weather. The infection began from April to May, and the disease occurred rapidly during the peak period from June to August, resulting in the rot and death of the injured orchid plants.

Prevention and cure method

1. Orchid white silk disease is easy to occur when the substrate is sour (pH less than 5.3), so mixing plant ash with a volume ratio of 10 in the substrate, or pouring 0.3% lime water to increase the pH value to about 6.5, can reduce the occurrence of white silk disease, and the effect is obvious.

2. The orchid matrix soil is disinfected with 0.2% pentachloronitrobenzene 500 times solution and 50% carbendazim wettable powder 600 times solution, or the rhizosphere and soil can be sprayed with pentachloronitrobenzene 500 times solution or 70% methyl thiophanate 800 times solution, or 50 grams of pentachloronitrobenzene powder mixed with 4 to 5 kilograms of semi-dry and wet fine sand, sprinkled on the rhizome of diseased plants to inhibit the spread of the disease.

3. In the rainy season from May to June in the south, the soil moisture is high, and white silk disease is easy to occur on the basin surface. The orchid should be quickly removed, the substrate infected with mycelium should be removed, the diseased root should be cut off, and 1000 times solution of potassium hyperoxylate can be sprayed to disinfect the root and wound. 1500 times solution of methyl topiramate can also be used to spray roots and wounds, and sprinkle fresh plant ash around the orchid root, then cover with substrate to protect the root, and then water the root after 2 to 3 days. If the matrix is wet, the rewatering can be postponed for 5 to 7 days, and the control effect is good.

4. During the occurrence of orchid white silk disease, 2000 times aqueous solution of medical chloramphenicol injection was used to sprinkle the diseased plants once a day for 3 times. Once the disease occurs, the diseased leaves should be cut off, the ventilation conditions should be improved, and the whole orchid should be soaked in 10% copper sulfate solution for disinfection. To the nearby orchid plant, also want to spray comprehensively, wet the base, basin surface, spray once a day, apply twice in succession, can control the disease, the control effect is good.

5. After the new buds of orchids grow out of the soil, 0.05% chloramphenicol is sprayed once a week for 2 to 3 times. If the potted soil is dry, this medicine can be used to prevent bacterial infection. It can also be sprayed with 1500 times aspirin solution, which can enhance the immunity of the orchid plant and prevent the invasion and spread of bacteria.

6. during the period of new bud extension and leaf expansion of orchid, medical penicillin, streptomycin, chloramphenicol or penicillin can be diluted to 2000 times, sprinkle the diseased plant, and spray comprehensively, once every 3 to 4 days, twice in succession, the control effect is good.

7. After the orchid attack, spray 50% benzoate wettable powder 1000 times, or 50% carbendazim wettable powder 500x, or 50% thiophanate wettable powder 500x liquid or 70% chlorothalonil wettable powder liquid 1000 times, every 7 to 10 days, spray 2 to 3 times, the control effect is good.

8. Orchids can be sprayed before and after overcast rain or before and after rain. 500 times of 50% Sukeling powder or 500 times of 50% Nongliling powder, 500 to 600 times of detoxification alum, and 300 times of Jinggangmycin water can be sprayed on stems, leaves and pots with remarkable control effect.