Herbicidal Selectivity and Mode of Action of EK-2612 in Rice and Barnyardgrass

EK-2612 [5-(2-3 dihydro-2,2,4,6,7-pentamethyl benzofuran-5-yl)-2-[1-(allyoxyimino) butyryl]-3 hydroxy cyclohex-2-en-1-one] is a new herbicide being developed for the selective post-emergence control of a wide range of grass weeds. It is a member of the class of cyclohexane-1,3-diones which inhibits chloroplastic acetyl-CoA carboxylase (ACCase, EC 6.4.1.2) and block fatty acid biosynthesis. A study was conducted to evaluate the herbicidal performances of EK-2612 especially on barnyardgrass and rice. The compound EK-2612 performed excellent post emergence activity against barnyardgrass exhibiting the growth inhibition of barnyardgrass by 74 and 84% at 60 and 120 g a.i. ha(-1), respectively. With increasing EK-2612 concentration, acetyl-CoA carboxylase activity was more inhibited in barnyardgrass than in rice. Chlorophyll content in barnyardgrass was reduced greatly with the increase of EK-2612 concentrations, whereas chlorophyll content in rice was not affected by EK-2612. No phytotoxic symptoms were observed on rice due to EK-2612, having a good rice safety up to the level of 120 g a.i. ha(-1). These results suggest that EK-2612 has an excellent pre-emergence herbicidal activity against barnyardgrass without hampering the growth of rice.