Illinois Pesticide Applicator Practice Test

What type of treatment is most effective against perennial weeds?

1. Contact herbicide

2. Systemic (translocated) herbicide

3. Pre-emergent herbicide

4. Foliar herbicide

The correct answer is: Systemic (translocated) herbicide

The most effective treatment against perennial weeds is a systemic (translocated) herbicide. This type of herbicide is designed to be absorbed by the plant and then transported throughout its system, effectively reaching the roots and other parts of the plant. Since perennial weeds have extensive root systems that allow them to survive and regenerate each growing season, a systemic herbicide can damage the entire plant, including its underground structures. Contact herbicides only affect the parts of the plant that they come into direct contact with and do not penetrate deeply enough to reach the roots, often allowing the weed to regrow. Pre-emergent herbicides are applied before weed seeds germinate, making them ineffective against established perennial weeds. Foliar herbicides may target leaf surfaces but lack the ability to move systemically within the plant, thus not effectively controlling roots of established perennials. Systemic herbicides are thus the best choice for effectively controlling these resilient weeds.