What is the primary difference between systemic and contact herbicides?

The primary distinction between systemic and contact herbicides lies in how they interact with plants. Systemic herbicides are specifically designed to be absorbed by a plant's foliage or roots and then transported through its vascular system. This means that once absorbed, the herbicide can affect the entire plant, including areas that were not directly exposed to the chemical application. This ability allows systemic herbicides to target and eliminate perennial weeds effectively by disrupting their physiological processes throughout all parts of the plant.

In contrast, contact herbicides function differently as they only affect the surface of the plant where the herbicide is directly applied. They do not penetrate into the plant tissues or travel throughout the plant, which makes them less effective against plants that have extensive root systems or where the herbicide cannot reach the inner tissues. Understanding this fundamental difference is crucial for effective weed management, as it guides the choice of herbicide based on the type of vegetation present and the treatment objectives.