12.8 Classifying Herbicides: Site of Action

The Site of Action is the specific biochemical pathway a particular herbicide acts upon in a plant. For example two different herbicides could both disrupt a plant’s ability to make amino acids (same Mode of Action) but how they do that can differ (different Sites of Action). Currently the Weed Science Society of America (WSSA) recognizes 19 Sites of Action. These sites of action are listed below with their associated Mode of Action. The group number indicated reflects the number WSSA has assigned to it, in parenthesis we also indicate the HRAC group assignment for anyone not working in the US.  An image representing the common damage symptoms is also included.  Damage symptoms will be revisited in later chapters.

Click through the presentation below to learn about the sites of action associated with each mode of action. The presentation also includes an image of damage symptoms from various herbicides.