Kaptan is a selective post-emergence herbicide containing a combination of Imazethapyr 35% + Imazamox 35% WG. When Kaptan herbicide is applied early post-emergence, absorption may occur through both the roots and foliage. Susceptible weeds stop growing and eventually die. Kaptan acts by inhibition of acetyl CoA carboxylase Accase. These chemicals block an enzyme called ACCase. This enzyme helps the formation of lipids in the roots of grass plants. Without lipids, susceptible weeds die.