Biological factors that are biological pathogens are also called pathogenic bacteria, invading the vegetation body to cause a small group of individuals, but the degree of harm is very large organisms, has always been in the place where there is vegetation, so far, through scientific research, has summarized some causes, the following to analyze one by one:
[1] Parasitic seed plants
Common parasitic plants are silkworm seeds, is a completely parasitic herb, climbing, rootless, the leaves have been degraded into scales, strong reproductive ability, can be seed reproduction, can also stem reproduction, with the help of climbables can be grown, can not be photosynthesis.
[2] Nematodes
Nematodes are a low-grade animal, the body is small, according to its own nature some grow in the soil, some parasitize in the roots of plants, some parasitize on the leaves of vegetation, the harm to flowers is very large, often causing the occurrence of diseases. Such as: chrysanthemum leaf wilt nematode disease.
[3] Phytoplasma
Pathogenic symptoms: yellowing, bushes, dwarfing, flower changes, etc., such as bubble hole bush disease, chrysanthemum yellowing disease. The bacteroid body is bounded between bacteria and microorganisms, the individual is larger than the virus and smaller than the bacteria, belongs to the lower cell organisms, mainly by plant grafting, leafhopper insects as the vector for transmission.
[4] Viruses
After vegetation is infected with the virus, the leaves or flowers appear growth deformity, clumps, plant shortness, internodal shortening, leaf shrinkage, local necrosis, yellowing, wrinkles, mottled, yellow-green flowers and leaves. Viruses have very small particles composed of nucleic acids and proteins, which are smaller than bacteria and can pass through ordinary filter paper and need to be highly magnified with a microscope. It is transmitted through various reproductive methods of insects and plants. Chrysanthemum virus disease, a string of erythrovirus disease.
[5] Bacteria
The bacterial body is smaller than the fungus, is a single-celled organism, but also a low-grade plant, using the method of division to reproduce, the bacteria that harm garden plants are soft rot, root cancer, bacterial leaf spot disease and so on.
[6] Fungi
Fungi are low-grade plants, visible under the microscope, multicellular bodies, can not make their own required nutrients, but there are vegetative organs and reproductive organs, reproduction and higher plants are similar, the conditions are suitable for the spore produced by wind, rain, insects and other spread infection, resulting in epidemic diseases.
