What is the function of protectant fungicides?

The function of protectant fungicides is to coat a plant as a barrier against pathogens. These fungicides are designed to be applied onto the surface of plants to prevent fungal infections by acting as a protective layer. This barrier helps to inhibit the entry of pathogens, thereby reducing the risk of disease development. Protectant fungicides are typically applied as preventative measures and are most effective when used before infection occurs.

In contrast, other methods or products mentioned in the options serve different functions. For example, some fungicides might be systemic, meaning they would absorb and circulate within the plant to address existing infections rather than merely providing a preventive coat. Additionally, promoting new plant growth is more associated with fertilizers or growth regulators rather than fungicides. Finally, while managing soil-borne pathogens is crucial in agriculture, that function typically aligns with soil sterilization practices or the use of certain nematicides or fungicides specifically designed for soil application, rather than the action of protectant fungicides.