What is the difference between chlorothalonil and carbendazim?

Chlorothalonil is a broad-spectrum protective fungicide. It is chemically stable, non-corrosive, of low toxicity to humans and livestock, and highly toxic to fish. It mainly controls a variety of fungal diseases, but it is not very effective against diseases caused by soil-borne Pythium species. For diseases that have developed resistance to carbendazim, switching to chlorothalonil for control can achieve good results. Carbendazim is a systemic fungicide. It is stable to heat, unstable to acids and bases, and has both protective and curative effects. Its systemic translocation is mainly acropetal. It is of low toxicity to humans, livestock, fish and bees, and it readily decomposes and loses effectiveness in soil. A so-called systemic agent is one that can be absorbed into the crop's body without losing effectiveness and can act on pathogens inside the plant. This kind of agent is also called a chemotherapeutic agent and is generally used on plants that are already diseased, but most systemic agents also have contact-killing effects. Carbendazim belongs to this category. A so-called contact agent is one in which the fungicide deposits on the plant surface and kills or inhibits the pathogen upon contact. This kind of agent either cannot be absorbed by the plant or, once absorbed, immediately decomposes and loses effectiveness, and it does not act on pathogens inside the plant. Chlorothalonil belongs to this category. (Feng Jun)