The first is the selection of fungicides. The selection of fungicides refers to active the differences between the control target and non-target, which usually be indicated by the degree of safety coefficient.

The second is the safety factor of fungicides that is the safety degree of Fungicides on plants. The highest concentration and recommended that the crops on the biocide can endure concentration ratio. When safety factor is more than 1, it can be used in the production; more than 2.5 is relatively safe.

The last is that safety factor affects the safety coefficient. Many factors influence the safety factor, including medicine categories and properties, types of crops, crop growth period, environment (humidity, temperature and pH of soil), and micro ecological system.