Which term describes substances used to control weeds?

Herbicides specifically refer to chemical substances that are formulated to control or kill unwanted plants, primarily weeds. This term is derived from the Latin word "herba," meaning "plant," combined with "cide," meaning "to kill." Herbicides are designed to target specific types of plants without damaging the desired crops, making them an essential tool in agriculture and landscape management.

In contrast, the other terms relate to different categories of pest control substances. Insecticides are used to control insects. Nematicides target nematodes, which are microscopic roundworms that can harm plants. Pesticides is a broader term that encompasses all chemical substances used to kill pests, which could include insects, weeds, fungi, and other organisms, but does not specifically refer to weed control. Therefore, "herbicide" is the most accurate term for substances used specifically to manage weeds.