Orchid disease-- fungal disease

Like other plants, orchid diseases are caused by pathogens, such as mold, bacteria, viruses, viroids, mycoplastids, parasites of parasitic plants, or physiological factors, such as nutrients, water, temperature, pollution, and so on. The following examples of mycosis are as follows:

The most important diseases of orchids are caused by fungi, accounting for at least 2% of the total diseases. Fungi are mostly small organisms that can only be seen under a microscope. It has no chlorophyll, can not produce nutrients, and has to absorb nutrients from living or dead plants, or even animals. Fungi consist of many branched filaments, namely hyphae. The mycelium can reach 1Oum in diameter and several meters in length, which can produce a large number of clasps. Hugs are spread by flowing air, water, insects or other animals.

The fungi that infect orchids are parasitic. They absorb nutrients from the host and destroy the tissue, thus causing many symptoms of the host, such as rot (the infected part decays), rust (the affected part is ferruginous), sudden collapse (rapid decay, resulting in the death of the whole seedling), wilting (turning brown and then dying), ulcers (local festering or sunken wounds), anthrax (ulcerative necrosis with black depressions), scab spots (slightly convex or sunken). Breakable), spots (foliar damage, including tissue death and collapse), mildew (infection partially covered with powder), tissue death, plant decay (reduced metabolism, blockage of vascular bundles, etc.).

Some fungi are parasitic on the surface of orchid plants and insert into epidermal cells with special hyphae; others grow between or around living cells; but most fungi indiscriminately pass through tissues (including cells) and cause them to die. The examination of mycosis must be observed under a microscope or transmission electron microscope, and the infected part needs to be specially treated and then sliced for observation. Identification needs the help of special reference books.

Because pathogenic fungi are transmitted through air and water. Direct contact with insects, other animals, humans, or plants themselves. Therefore, in order to prevent the disease, we should first pay attention to cleanliness and hygiene, develop good horticultural practice and operation habits, and control the infectious vector in order to put an end to the source of the disease. Only when the above measures are not effective can it cause fungal disease and be forced to use chemicals.

As far as we know, there are more than 30 genera and 100 species of fungi harmful to orchids. The more common genera are Collectotrichum, Sclerotium, Botrytis, Phytophthora, Fusarum, Uerdo, Coleosporium and so on. (Chen Xinqi, Ji Zhanhe)