Abstract
This study was carried out to identify thiolcarbamate compounds with superior intergeneric selectivity between rice and barnyardgrass (Echinochloa oryzicola), that could be safely applied during the germination and seedling stages of rice.
1) In the substitution of the thiolcarbamate compounds, it was essential for the enhancement of the selectivity between rice and barnyardgrass that the amine part be a cyclic amine and ester part belong to the cumyl group (α, α-dimethyl-benzyl group) (Tables 2-6).
2) Dimepiperate (S-1-methyl-1-phenylethylpiperidine-1-carbothioate) was selected out of 65 substituted thiolcarbamate compounds due to it's high herbicidal activity against barnyardgrass, it's structure consists of a cyclic amine with 5 methylene rings, as in the case of piperidine. Dimepiperate exhibited a higher selectivity toward seeded rice than thiobencarb and molinate (Figs. 1-2).
3) In the pot tests carried out in the greenhouse under submerged conditions, dimepiperate showed a higher herbicidal activity in the pre than post emergence treatment of Echinochloa oryzicola (Eo), Monochoria vaginalis (Mv) and Scirpus juncoides (Sj). The herbicidal activity of this compound which was particulary high against Eo was comparable to that of thiobencarb and molinate, but was lower against Mv and Sj than that of the conventional herbicides.
