What is the definition of a contact herbicide?

A contact herbicide is defined as a substance that kills weeds or unwanted plants upon direct contact with their foliage or other parts. When applied, contact herbicides quickly affect the plant cells they touch, leading to cell damage and ultimately plant death. This action is typically swift, as the herbicide does not need to be absorbed and translocated through the plant system. It is effective on annual weeds and certain smaller perennial weeds but might not be as effective on larger, established plants since areas of the plant that do not come into direct contact with the herbicide will remain unaffected.

Understanding the impact of contact herbicides is important in weed management strategies, as they require precise application to ensure sufficient coverage of the target plants. This characteristic differentiates them from other types of herbicides that might rely on absorption through the roots or leaves or that translocate through the plant system, impacting areas away from the initial point of application.