According to the survey, there are more than 80,000 kinds of pathogenic microorganisms (fungi, strong bacteria, rickettsia, mycoplasma, viruses, algae, etc.) harmful to plants all over the world. Plant diseases cause huge losses to agriculture, and crops around the world are thus reduced by an average of about 500 Mt per year.
In history, there have been many disasters caused by a certain plant disease epidemic, causing severe famine and even starving a large number of people. The use of fungicides is a cost-effective method of controlling plant diseases.