Critical tests regarding current residual-spray control against medical insects in Japan : I. Effect of DDT, γ-BHC and diazinon against houseflies as applied in model-huts

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  • 衛生害虫に対する殺虫剤残留噴霧の再検討 : 第 1 報イエバエに対する DDT, γ-BHC 及び diazinon の効果について
  • 衛生害虫に対する殺虫剤残留噴霧の再検討-1-
  • エイセイ ガイチュウ ニ タイスル サッチュウザイ ザンリュウ フンム ノ サイケントウ 1

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In order to check the actual fly control efficiency of the residual insecticide a series of spray tests were carried out utilizing small summer-huts located in a small valley in Hachioji-city west of Tokyo. Using ten huts (each hut has an area of 9.8m^2, and the windows are kept closed throughout the test) spray was made on the ceiling in ratio 50cc per square metre which is the standard dosis in this country. Flies of susceptible as well as resistant strains were introduced at certain intervals during 200 days beginning September 20, 1961, and their knockdown was counted. 1. Residual spray of 5% DDT emulsion gave a knockdown of merely 50% or less when the temperature is high (25-28℃), while it gave about 80% knockdown when the temperature is 20℃ or lower through six months, but never reaches 100%! 2. Residues of 0.5% γ-BHC emulsion gave 70-90% knockdown for about one week after spray against susceptible flies (Takatsuki-strain), but the value comes low down to 50% by one month. A moderately resistant Kamata-strain (resistant ratio about three times of Takatsuki-strain) showed only 15% knockdown by one week and none was affected after one month. 3. It was clearly shown that the knockdown effects of DDT and γ-BHC were always superior in the shadowy huts located among the trees to the same in the huts located in open grassy place. This may be due to the facts that the housefly remains longer on the ceiling in a dark room and the residue does not quickly disappear in the huts among trees where the temperature was kept comparatively low. These conditions naturally accelerate the effect of DDT than the same of γ-BHC. 4. Residue of 0.5% diazinon emulsion showed 100% knockdown effect against susceptible (Takatsuki) strain until 7 days after spray, it fell down to 60% by one month, 0% after six months. When a diazinon resistant strain (RP-strain, resistance 10 times to standard strain) was introduced, it yielded only 16% knockdown even by 7 days, and reached 0% by 20 days!

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