Abstract
Safening action of dimepiperate in rice plant (S-1-methyl-1-phenylethylpiperidine-1-carbo thioate) was examined.
1) Dimepiperate showed an obvious safening action on herbicides inhibiting root growth, such as pendimethalin, clomeprop, MCPB, bensulide and bensulfuron methyl (Table 3). The action was markedly different from that of usual safeners.
2) Safening action of dimepiperate in rice plant was more remarkable than that of other herbicides (dimepiperate>thiobencarb>>mefenacet) (Fig. 2). Dimepiperate alleviated the root injury caused by bensulfuron methyl, and the optimum dose for the ratio of bensulfuron methyl/dimepiperate was 1:3-1, 000 (Tables 4, 5, Fig. 1).
3) Safening effect of dimepiperate on the auxin-type herbicides MCPB, Phenothiol and clomeprop was manifested by the alleviation of the root injury caused by these compounds. It is suggested that the addition of dimepiperate enable to extend the application period, while MCPB and phenothiol cannot be applied to the rice plant beyond the 5-leaf stage (Fig. 3). The safening effect of dimepiperate may contribute significantly to the alleviation of the phytotoxicity caused by auxin herbicides which is observed at high temperatures (Fig. 4). Though the mixture rate of dimepiperate and auxin herbicide required to achieve both a herbicidal and safening effect, has not been fully investigated the range of 1:1-30 for the auxin herbicide and dimepiperate (Tables 6, 7) is proposed.
