Abstract
The residual behavior of Bayer product S 4741 was examined by use of 32P-radiotracer. It was found that the insecticide was rapidly penetrated and translocated into citrus and rice plant, irrespective of any application methods. The degradation rate of the insecticide, examined by chloroform-water partition coefficient of radioactive material in citrus leaves, had a similar tendency in both cases of spray and topical applications. In orange fruit, the insecticide residue was higher in peel than juice on the eighth day after the application. The accumulation of the insecticide in top leaves of apple tree after the topical application on the stem base was similar to that in citrus leaves, but the degradation rate of the insecticide was slow as compared with that of citrus leaves.
The behavior of the insecticide sprayed on garden radish and sugar beet, was rather different between both plants, and the accumulation of radioactive material in root was higher in sugar beet than garden radish. This fact would be due to the difference of growth rate during the experimental period. The partition coefficient of radioactive material in roots was always lower than that in leaves of both plants. When the roots of rice seedlings were dipped into the water emulsion of the insecticide before the transplantation, the insecticide was rapidly taken up by the seedlings. About forty-one per cent of available insecticide in the water emulsion was taken up by the seedlings during 24 hours' root application. When the insecticide suspension was poured into the paddy water after the transplantation of seedlings, the major part of insecticide was distributed in leaf sheath and leaf blade but the distribution in root was very low. This fact may show that the insecticide penetrated into plant body mainly through the surface of leaf sheath but not through root.
After the penetration of the insecticide into plant tissues, mercaptosulfur moiety of the insecticide molecule was oxidized to produce the sulfone such as the case of systox. Phosphoric acid and dimethyl phosphoric acid were found as the hydrolysis products of the insecticide by ion exchange chromatography, and the production ratio of these metabolites was different among the test plants.
