How do contact herbicides interact with plant tissues?

Contact herbicides operate by affecting only the plant tissue directly exposed to them. When these herbicides are applied, they penetrate the outer layers of the plant and disrupt cellular functions in that specific area. This localized effect means that any portions of the plant that do not come into direct contact with the herbicide remain unaffected.

This characteristic is crucial in managing weeds or unwanted vegetation because the goal is often to target specific plants without harming surrounding crops or desirable plants. Because contact herbicides do not enter the vascular system of the plant or induce systemic responses, they are typically effective for immediate control of annual weeds or plants that can be physically overgrown or shaded out once the upper portions are damaged.