There are two ways of action of fungicides: one is a protective fungicide, and the other is a systemic fungicide. The protective fungicide directly contacts the pathogenic bacteria in vitro or on the surface of the plant, killing or inhibiting the pathogenic bacteria, making it unable to enter the plant, thereby protecting the plant from the pathogen. These fungicides are called protective fungicides. They have two functions: one is to contact the pathogen after spraying, and directly kill the pathogen, that is, "contact sterilization"; the other is to spray the agent on the surface of the plant. In the above, when the pathogenic colony is exposed to the agent on the plant body and is poisoned, it is called "residual bactericidal effect".

Different fungicides work differently. It is called a protective fungicide, that is, a protective agent, which is applied to the surface of plants before the infection of the pathogen; it can eliminate the infected bacteria at the application site, and is called a scavenging fungicide; it can be absorbed by plants and The system is called a systemic fungicide, which is also a systemic fungicide. Many scavengers are also systemic. Most of them have chemotherapeutic effects. Therefore, it is often practical to simply separate the bactericide into two modes of action: protective and systemic.