Certified Crop Advisor Practice Exam

What is the mode of action for systemic fungicides?

1. To kill the pathogen on contact

2. To prevent disease through plant uptake

3. To change soil pH

4. To disrupt pest communication

The correct answer is: To prevent disease through plant uptake

The mode of action for systemic fungicides is centered on their ability to be absorbed and transported throughout the plant, which allows them to provide protection from diseases. When these fungicides are taken up by the plant roots or leaves, they circulate through the plant's vascular system, making them effective against pathogens that may attack various tissues. By preventing disease through plant uptake, systemic fungicides can inhibit the growth and reproduction of fungi before they can establish a significant infection. This proactive approach allows the plant to maintain its health and yield potential while minimizing the impact of pathogen presence. The systemic nature of these fungicides means they can protect not only the areas of the plant that were treated but also other parts that may come under attack later. In contrast, fungicides that operate by direct contact primarily aim to kill pathogens on the surface of plants but do not provide the same level of systemic protection or longevity. Additionally, options referring to changing soil pH or disrupting pest communication do not relate to the action of systemic fungicides, as these processes are associated with different agricultural practices and types of crop protection products.