What is the key difference between systemic and contact herbicides?

Systemic herbicides are specifically designed to be absorbed by the plant and then translocated through its tissues. This movement allows the herbicide to affect the entire plant, including parts that are not directly exposed to the herbicide application. When a systemic herbicide enters a plant, it can travel through the xylem and phloem, reaching various tissues and ultimately leading to the death of the whole plant, including the roots and leaves.

This mode of action is particularly useful for controlling perennial weeds, as the herbicide can reach and disrupt vital processes throughout the plant, not just the parts that were touched by the herbicide. In contrast, contact herbicides only affect the parts of the plant they come into direct contact with, typically causing damage or death to the foliage but not impacting the roots or untreated areas. Understanding this difference is crucial for effective weed management, as the choice between systemic and contact herbicides depends on the specific plant species and the desired outcome of the treatment.