What characterizes a "contact fungicide"?

A "contact fungicide" is specifically designed to remain on the surface of the plant where it has been applied. This means that it functions by preventing fungal spores from germinating or disrupting the structural integrity of established fungal pathogens that come into contact with it. Because contact fungicides do not translocate within the plant, their protective effects are limited to the areas that have been treated. This is a crucial aspect because it dictates how and when these products should be applied to be effective against various fungal diseases.

In contrast, a fungicide that moves within the plant to provide long-term protection would be referred to as a systemic fungicide, thereby highlighting the difference between these two classes of fungicides. The effectiveness duration of contact fungicides, while often in the range of weeks, can differ based on environmental factors and specific products; thus, it's not a defining characteristic for their classification. Additionally, while contact fungicides may be useful for treating foliar diseases, they are generally not suited for root and crown problems since their action is limited to the above-ground parts of the plant. Therefore, the definition of contact fungicides is centered around their application method and mechanism of action on the surfaces of plants.