Fungicides are a major category in the pesticide market, and different fungicide products have different mechanisms of action, which can be basically divided into the following four categories.

1. Protective bactericide

The main mode of action of the protective fungicide is to form a film on the surface of the plant after the application of the fungicide, so that the pathogen can not be infected.

Such fungicides are particularly effective for air borne pathogens, such as Bordeaux solution to control downy mildew of various crops; treatment of plant seeds or seedlings to prevent the infection of seed borne diseases, such as Triadimefon seed dressing to prevent black ear disease of cereal; carbendazim dip in sweet potato seedlings to prevent seedling diseases; Formica and Carbendazim soil treatment to prevent soil borne diseases of various crops, such as suddenness Lodging and blight, etc.

2. Eradicative fungicide

This kind of fungicide has a direct and strong killing effect on pathogenic bacteria, but the plants can't bear this kind of fungicide in the growing period of plants, so it can only be used for soil treatment, plant dormancy period or seedling treatment before sowing.

It is common to disinfect the seeds with formalin and tebuconazole can eliminate wheat stripe rust and powdery mildew.

3. Therapeutic bactericide

After the plant is infected, some non inhaling fungicides, such as sulfur, can be used to kill the bacteria directly, or the fungicide with the function of infiltration can be used to penetrate into the interior of the plant tissue, kill the bacteria, or the fungicide with the function of treatment with the transportation and transmission of the plant body fluids.

The common ones are carbendazim, tobuzin, chunleimycin, azoxystrobin and chlorothalonil.

4. Antiviral activator

This kind of fungicide is the activator of plant disease resistance, which can induce the whole plant disease resistance by identifying the pathogen. However, the fungicide can not directly show fungicidal activity, but can be resistant to disease for a long time after use, so it is not easy to produce resistance.

The common agents are oxalic acid, benzothiadiazole and allylbenzothiazole.