What is the primary mode of action for contact herbicides?

Contact herbicides function by targeting and affecting the parts of the plant that they directly touch. Unlike systemic herbicides, which are absorbed and translocated throughout the plant system to affect various tissues, contact herbicides operate on a more immediate basis. When applied, they disrupt cellular processes in the plant tissues where they land, leading to the death of those specific areas.

This mode of action makes contact herbicides particularly effective for controlling annual weeds or those that do not have extensive root systems, as they need to come into direct contact with the foliage for effective control. The effectiveness of contact herbicides is contingent upon adequate coverage of the weed's foliage, as any area that does not receive the chemical will not be affected. Therefore, understanding the primary mode of action of contact herbicides is crucial for achieving successful weed management in right-of-way applications.