Illinois Field Crop Applicators Practice Test

Which type of herbicide is characterized by symptoms like corn with rolled leaves?

1. Photosynthesis inhibitors

2. Growth regulator

3. Contact herbicides

4. Herbaceous inhibitors

The correct answer is: Growth regulator

The type of herbicide characterized by symptoms like corn with rolled leaves is a growth regulator. Growth regulators affect the plant's growth processes, often disrupting normal hormonal functions, which can lead to visible stress signs such as leaf rolling. This symptom occurs because these herbicides can cause a plant's response to an imbalance in growth favored by these chemicals, often seen when they are misapplied or when the crop is sensitive to them. Understanding the effects of growth regulators is important for applicators as they can lead to significant crop damage if not used properly or if the crop variety is particularly sensitive. Other herbicide classes, such as photosynthesis inhibitors or contact herbicides, have distinct action mechanisms and symptoms that do not typically manifest as rolled leaves in corn. Photosynthesis inhibitors would more likely cause chlorosis or necrosis, while contact herbicides would show symptoms of burn or desiccation limited to the area where the herbicide touched the plant, rather than a systemic response like leaf rolling. Herbaceous inhibitors is a less common term and would not specifically relate to the symptom described. Thus, growth regulators are the appropriate choice in this scenario due to the specific symptom associated with their mode of action.