Special terminology for plant diseases

1. Plant non-infectious diseases

Due to the unsuitable growth conditions or the influence of harmful substances in the environment, there is no infection of other organisms, so it can not be transmitted to each other, so it is generally called non-communicable diseases.

2. Plant infectious diseases

Compared with non-infectious diseases, plants are parasitized by pathogens to cause infectious diseases, which can also be called parasitic diseases or infectious diseases.

3. A general term for organisms that cause plant diseases. Fungi, bacteria (mycoplasma), viruses (viroid), nematodes and parasitic seed plants are known. In addition, a small number of actinomycetes and algae can also infect plants, such as potato scab caused by actinomycetes (Actinomyces scabies) and red rust algae (Cephaleuros virescens) on tea and many other evergreen trees.

Most plant diseases are caused by fungi, and hyphae are the most common vegetative structure of fungi. Spores are usually produced in the stage of sexual planting, which is the main source of primary infection of plant diseases.

4. Parasitic parasites must obtain the biological characteristics of living substances (water, nutrients, etc.) from the cells and tissues of living hosts for their own growth and development.

It can be divided into specific parasitism and facultative parasitism, which means that parasites must live on living hosts under natural conditions in order to grow and develop; facultative parasites can not only live on host organisms, but also engage in saprophytic life in dead bodies or organic matter.

The vast majority of plant pathogenic fungi and all plant pathogenic bacteria are facultative parasites.

5. The characteristics of diseases caused by pathogenic pathogens infecting host plants.

6. the symptoms of the disease are discoloration, necrosis, decay, wilting and deformity.

Discoloration: refers to the change of the original color of diseased plants, which is the most common and earliest type of disease. Discoloration is usually the most obvious in the early stage of viral disease, and there are many types of discoloration, such as mosaic, yellowing and streak. Plant viral diseases and some non-infectious diseases (especially element deficiency) often show discoloration symptoms.

Necrosis: the death of a local or large area of diseased tissue. Commonly seen are: leaf spots, withered spots, leaf withering, branch withering, ulcers, standing withering, perforation, and so on.

Decay: diseased tissue is affected by various enzymes and toxins of bacteria, pectin and cell wall are broken down, cells are destroyed, and the original tissue structure and appearance are disintegrated. It can be divided into dry rot and wet rot (soft rot).

Wilting: the vascular bundle of the root or stem of the diseased tissue is necrotic and loses its transport function, especially the ductal system is seriously damaged, and the water in the root can not be transported upward, resulting in the drooping of aboveground branches and leaves.

Malformation: abnormal growth of local tissue of plants stimulated by hormones of pathogens, which is generally characterized by proliferation, proliferation and reduction.

7. Infection cycle of disease

The disease began to occur in the previous growing season and continued again in the next growing season. It is composed of pathogen primary infection, re-infection, overwintering (or summer) and transmission.

Primary infection: an overwintering or summer pathogen that causes the initial infection after the plant begins to grow.

Re-infection of plants infected for the first time can produce spores or other vegetative forms, which can cause re-infection after transmission, and most plant diseases may occur multiple infections in one season.

8. Transmission of pathogens the process in which pathogen inoculum spreads from the source of infection. Most pathogens can be transmitted by airflow, water flow, mediators (insects, mites, fungi), soil and man-made.

9. The degree of disease includes morbidity and severity, which generally refers to the percentage of disease in diseased fields, plants or organs, while severity refers to the degree of damage to plants or organs in the field.

10. Plant disease control is based on the principle of system cybernetics, and the optimal disease management method is selected to keep the occurrence of plant disease below the level of economic damage. At present, for the treatment of diseases, we mainly adopt the policy of giving priority to prevention, comprehensive prevention and advocating ecological management. The occurrence and spread of diseases can be controlled by means of plant quarantine (legal control), agricultural control, disease resistance breeding, chemical control, biological control and so on. (it clears up when it snows fast)