Illinois Field Crop Applicators Practice Test

For optimal effectiveness, why should herbicides be mixed or combined?

1. To restrict weed growth only

2. To broaden the spectrum of weeds controlled

3. To increase costs

4. To reduce application time

The correct answer is: To broaden the spectrum of weeds controlled

Mixing or combining herbicides is vital for broadening the spectrum of weeds controlled. Different herbicides have varying modes of action, meaning they target different biochemical pathways in plants. By combining herbicides, an applicator can effectively tackle multiple weed species at once, greatly increasing the overall efficacy of the weed control strategy. This approach enhances control over a wider range of weed types, including those that may have developed resistance to a single herbicide. Moreover, a mixed application can often lead to a more effective and sustainable weed management program, reducing the likelihood of weed population rebound and resistance development. Options that focus exclusively on restricting weed growth may not account for the practical benefits of combining herbicides, such as improved effectiveness. Additionally, increasing costs or reducing application time are not primary justifications for mixing herbicides; the emphasis should always be on achieving the best control possible across the varied weed populations present in the field.