The protective agent treats the plant or the surrounding environment with the agent before the pathogenic microorganism does not contact the plant or is not immersed in the plant body, so as to inhibit the germination of the pathogenic spore or kill the germinal pathogenic spore to protect the plant from its damage. This effect is called protection. effect. Agents with this effect are protective agents. Such as Bordeaux liquid, daisen zinc, copper sulfate, green milk copper, mancozeb, chlorothalonil, etc.
The pathogenic microorganism of the therapeutic agent has been immersed in the plant, but the plant manifests the disease in a latent period. The drug penetrates into the plant tissue from the plant epidermis, and is transduced, diffused, or produces metabolites to kill or suppress the pathogen, so that the diseased plant is no longer harmed and restores health. Agents with such therapeutic effects are called therapeutic agents or chemotherapeutic agents. Such as thiophanate-methyl, carbendazim, kasugamycin and so on.