Fungicides are also known as biocides, bactericidal algaecides, microbicides, etc. They usually refer to chemical agents that can effectively control or kill microorganisms in the water system-bacteria, fungi and algae. In the international arena, it is usually used as a general term for the prevention and treatment of various pathogenic microorganisms.
According to investigations, there are more than 80,000 kinds of pathogenic microorganisms (fungi, strong bacteria, rickettsia, mycoplasma, viruses, algae, etc.) harmful to plants in the world. Plant diseases have caused huge losses to agriculture, resulting in an average annual reduction of about 500Mt of crops in the world. There have been many disasters in history that caused severe famines due to the prevalence of certain plant diseases, and even starved to death of a large number of people. The use of fungicides is an economical and effective method to prevent and control plant diseases.
There are two modes of action of fungicides: one is protective fungicides, and the other is systemic fungicides. Protective fungicides directly contact with pathogens outside or on the body surface of plants to kill or inhibit pathogens so that they cannot enter plants, thereby protecting plants from the harm of pathogens. Such fungicides are called protective fungicides, and their effects are in two aspects: one is to directly kill the pathogens after spraying with the pathogens, that is, "contact sterilization"; the other is to spray the pesticides on the surface of the plant. In the above, when the pathogenic colony comes into contact with the medicament on the plant body and is poisoned, it is called "residual bactericidal effect".