Does the questioner want to ask "What means are used to achieve plant protection through chemical killing?" It is achieved through direct contact, gastric poisoning, fumigation, etc.
1. Direct contact: Oxygen chemical killing can achieve the purpose of prevention and control by directly contacting the plant surface to poison the pests or pathogens.
2. Stomach poisoning effect: Xiaoyin chemical killing can also cause the pests or pathogens to be poisoned and die after eating them through the stomach poisoning effect in the crops.
3. Fumigation effect: Xiaoyin chemical killing can also achieve the purpose of prevention and control by fumigating pests or pathogens in the air.