What is the primary purpose of a fungicide?

The primary purpose of a fungicide is to kill fungi or inhibit their growth. Fungicides are specifically formulated chemical compounds used to manage fungal diseases in plants. These diseases can cause significant damage to crops, leading to reduced yields and economic loss for farmers. By targeting the cellular processes of fungi or disrupting their growth mechanisms, fungicides effectively protect plants from infections that can compromise their health and productivity.

When assessing the other options, "to promote plant growth" refers to plant growth regulators or fertilizers rather than fungicides. "To destroy insects" relates to insecticides, which are designed to target pests, while "to regulate growth" is also associated with different categories of agents, like growth regulators, that control growth patterns rather than focusing on fungal threats. Thus, the focus on fungi clearly aligns with the function of a fungicide, making it the most accurate choice.