Certified Crop Advisor Practice Exam

Herbicides are usually most effective on which type of plants?

1. Fast growing plants

2. Slow growing plants

3. Perennial plants

4. Woody plants

The correct answer is: Fast growing plants

Herbicides are typically most effective on fast-growing plants due to their growth stages and physiological processes. Fast-growing plants tend to absorb herbicides more readily, as they are actively taking in nutrients and water to support their rapid development. This increased uptake facilitates the herbicide's action, allowing it to work more efficiently in disrupting metabolic activities linked to growth. In contrast, slow-growing plants generally have lower rates of nutrient absorption, which can limit the effectiveness of herbicides. Perennial plants, which have established root systems and may develop tolerance to certain chemicals over time, can also resist herbicidal action more than annual fast- growing plants. Woody plants similarly possess lignified tissues that may establish barriers to herbicide penetration and absorption, reducing the likelihood of effective control. Thus, the dynamic growth pattern of fast-growing plants creates an environment in which herbicides can exert their maximum effectiveness.