Illinois Pesticide Applicator Practice Test

What defines a systemic herbicide?

1. It kills on contact

2. It is absorbed and translocates through the plant

3. It is effective only in dry conditions

4. It is safe for all plant species

The correct answer is: It is absorbed and translocates through the plant

A systemic herbicide is defined by its ability to be absorbed by the plant and then translocated throughout its various tissues. This means that when the herbicide enters the plant, it moves through the plant's vascular system to reach the areas that are growing or actively metabolic, including roots, stems, and leaves. This characteristic enables systemic herbicides to effectively control a wide range of weeds, especially perennial ones, by disrupting their physiological processes from within. The other options do not describe systemic herbicides accurately. For instance, a contact herbicide is one that kills the plant on contact and does not need to be absorbed to be effective. The effectiveness of a herbicide in dry conditions refers more to its mode of application and its absorption by the plant rather than its systemic properties. Lastly, safety for all plant species does not define a systemic herbicide, as many systemic herbicides can be harmful to desirable plants as well, depending on application methods and concentrations.