1) 본 시험은 malathion이 방충제로 사용되었을 때 자연적인 곡물저장조건하에서의 잔류효력과 그의 지속성을 검정하기 위해서 1963년 6월부터 9월에 걸쳐 행하였다. 2) 백미를 malathion 유제로 처이하고 일령 21일된 쌀바구미를 일정기간마다 8일간 접종하여 살충율을 을 조사하고 이로서 malathion의 잔류효력과 지속성을 판정하였다. 3) 처리후 8일까지는 각 실험농도에서 의 살충율을 나타내었고 32일에서 8ppm과 16ppm은 의 살충율을 보였으나 4ppm과 2ppm에서는 각각 와의 살충율을 보였다. 32일 이후에서는 어느 농도에서나 의 살충율은 볼 수 없었고 107일에 이르러서는 각 농도간 살충율에 차가 없었다. 4) 처리한 malathion의 반감기는 즉의 살충율을 나타낸 것은 2ppm에서 33일, 4ppm에서 54일, 8ppm에서 73일. 16ppm에서 93일 이었다. 5) 자연곡물저장조건하에서 malathion 잔류효력을 5개월간 보지하려면 본 실험에서 사용한 농도보다 훨씬. 높여야 될 것으로 생각된다.

1) This experiment was planned to determine the biological effectiveness and persistence of malathion residues on the polished rice under the natural storage conditions in Korea from June to September in 1963). 2) Whole kernel rice was treated with malathion as a spray. The test insects(21 days old were exposed) for a period of 8 days at given day intervals, 3) The biological effcetiveness and persistence of malathirm residues on the polished rice was determined as the mortality of the rice weevils, Sithophilus oryzas L. 4) It was observed from Table 1 and Fig. 1 that 100 per cent mortality was resulted in at 3 days from treatment in all dosages used in this experiment. At :1':days after treatment, the dosages of 16ppm and 8ppm gave still 100 per cent mortality, but the dosages of 4 ppm and 2 ppm resulted in per cent mortalities, respectively. After 32 days from the treatment,the mortalities in all dosages used did not show any 100 per cent mortality, At. 107 days after treatment, there was no any difference in the mortality of weevils inall dosages used. 5). It was observed from Fig. 1 and Table 2 that the half-life values of malathion residues on the polished rice was 33 days at 2 ppn!, 54 days at 4 ppm, 73 days at 8 ppm, and 93days at 16ppm, respectively. 6). To get a satisfactory control of the rice weevile with the malathion-residues for more than 5 months under the natural storage conditions, it may be necessary to use higher dosages than those used in this experiment.

• YOUNG EYUN CHOI