Studies on the effects of several insecticides against adult cockroaches, Blattella germanica L. and Periplaneta japonica K.

Laboratory tests were conducted to determine the effects of several insecticides against two species of cockroaches, Blattella germanica L. and Periplaneta japonica K.. The result are summarized of follows : Topical application method : By the application of 18μg per roach of the toxicants allethrin, DDVP, γ-60% BHC and diazinon, gave higher knockdown effcets than lindane and malathion. Those of dieldrin, aldrin and endrin were inferior to the above insecticides. Crude DDT and p-p' DDT caused no knockdown effect for five hours after treatment. However, in the mortality after 24 hours, dieldrin aldrin, endrin, allethrin and DDVP were almost at the same level and were more effective than the other chemicals. Similar results were obtained by treatment with 1.8μg per roach of toxicants except allethrin, which showed fairly low effect at this doses. Contact method : When Blattella germanica was brought into contact with glass plate of 100cm^2 treated by 0.5cc of 1% aceton solution of the toxicant, the order of knockdown effect was as follows : Allethrin>DDVP>γ-60% BHC>diazinon>lindane, malathion>dieldrin, aldrin, endrin, crude DDT, p-p' DDT. And with filter paper treated by the same amount of toxicant, the order changed as follows : DDVP>γ-60% BHC>allethrin>lindane, diazinon>dieldrin, endrin, crude DDT>malathion, p-p'DDT. During the observations on the mortality at 6 days after the treatments, DDVP, γ-60% BHC, diazinon, lindane and allethrin were only slightly more effective than the other chemicals, and all the chemicals tested showed of mortality over 95%. In the tests on the relationship between the time of exposure and the mortality with different insecticidal residues, dieldrin showed highest effects as 100% kill by 5 minute's exposure, while the similar effects were observed by 1 hour's exposure of diazinon and lindane. DDT was less effective on both B. germanica and P. japonica than the other chemicals through the test method discussed above.