Herbicide mode of action

The pesticide mode of action is a fundamental aspect not only in development but also in the exploration of the molecular mechanisms of the biological effect. Novel modes of action are essential to avoid the detrimental side effects of formerly introduced compounds and to prevent or mitigate pest resistance, but, as of this writing, the most recently marketed herbicide with a novel mode of action was introduced in 1992. Meanwhile, increasing requirements for toxicology testing increase the cost of development. The development of genetically modified crops resistant to damage by existing herbicides had the negative effect of impeding the development of novel agents. Herbicides are classified by the target site of action; three overlapping systems are now used.