There is a growing need for herbicides with new modes of action.
Natural compounds offer an abundant source of evolved phytotoxins with new target sites.
Each of these has a unique mode of action. Usnic acid, a product of certain lichens, is a more potent inhibitor of HPPD than commercial herbicides with this target site. We discovered that the herbicide cinmethylin is bioactivated in plants to become an analogue of 1,4-cineole that is a potent inhibitor of asparagine synthetase. These and other unique natural product modes of action will be discussed.