This presentation will describe the basics of herbicide modes of action, use of pre-emergence vs post-emergence, and the difference in system and contact herbicides. There are many reasons that herbicides may not perform as expected and many practices that can increase the likelihood of drift and environmental loss of herbicide products. We will go over the various application, environmental and equipment variables that can cause weed control failures and what you can do to maximize herbicide effectiveness while minimizing drift and unintended herbicide movement.