J. Pestic. Sci., 32(3), 249–254 (2007)

Barnyardgrass (Echinochloa spp.) is one of the most common and troublesome weeds in paddy rice cultivation. For effective barnyardgrass control, herbicides with high efficacy against the weed and good selectivity for rice are required. 1-Phenyl-5(4H)-4-dialkylcarbamoyltetrazolinones exhibited high activity against barnyardgrass in paddy field experiments. Fentrazamide, 4-(2-chlorophenyl)-N-cyclohexyl-Nethyl-4,5-dihydro-5-oxo-1H-tetrazole-1-carboxamide, has been developed as a rice paddy herbicide for controlling barnyardgrass. In Japan and Korea, this compound is applied at the time of rice transplanting due to its long residual activity. It shows excellent efficacy against barnyardgrass with a wide application range from pre-emergence up to the three-leaf stage with good compatibility with transplanted rice. Several morphological studies revealed that phytotoxic symptoms of fentrazamide were similar to those of oxyacetamides inhibiting cell division. Fentrazamide and mefenacet were shown to inhibit cell division in meristematic areas in Echinochloa spp. based on microscope observations. Reductions in the length of young leaves, the number and length of coronal roots, leaf sheaths and leaf blades were also reported. Some physiological and biochemical studies reported that fentrazamide inhibited the formation of very long chain fatty acids (VLCFAs), similar to chloroacetamides and chloroacetanilides. The incorporation of [C]-oleic acid into sporopollenin, which mainly consists of VLCFA in a green alga Scenedesmus acutus, was sensitive to 0.1 to 1 mM of fentrazamide, similarly to chloroacetanilides which inhibit fatty acid modification. Fentrazamide also caused losses of saturated VLCFAs with the carbon number of 20, 22, and Action of fentrazamide on protein metabolism and cell division in plants