What do contact herbicides require compared to translocated herbicides?

• A. More time to work
• B. Better spray coverage
• C. A smaller droplet size
• D. Higher pressure application

Answer: (B)

Contact herbicides are designed to kill the parts of the plant that they come into direct contact with. This means that for them to be effective, they need to thoroughly cover the target vegetation, so better spray coverage is essential. The active ingredients in contact herbicides do not move within the plant, and their effectiveness is largely dependent on how well they coat the leaf surfaces and other plant tissues.

In contrast, translocated herbicides, or systemic herbicides, are absorbed by the plant and then move throughout its tissues to affect areas such as the roots and stem. This mechanism allows them to be effective even if only part of the plant is treated.

While droplet size and pressure can affect the application process, they are not as inherently required for the efficacy of contact herbicides as the necessity for comprehensive spray coverage. Similarly, the time needed for contact herbicides to work is not necessarily longer than that for translocated herbicides, which may also require time to translocate and show effects. Hence, better spray coverage is the critical factor that differentiates the application of contact herbicides from translocated ones.