Studies on the bioassay method of insecticides against fly-maggots I : Relationship between the volume of the used diluent and the LC_<-50> value

Abstract

It is anticipated that the effect of fly-maggots larvicide is influenced by the absolute volume of the used diluent under "the dilution contact method", in which the test insects are exposed to a certain depth of, or a thin layer of, insecticide dilution for 48 hours and mortality counts are made. The relationship between the used volume of lindane emulsion at the various concentrations and the LC-50 value was investigated using last inster larvae of the flesh fly, Boettecherisca peregrina (Rovineau-Desvoidy), in a test cotainer of 9cm diameter and 6cm in height. The volume of the each diluent was 1, 2, 4, 8 and 16ml, respectively. Through this investigation, it was experimentally confirmed that the relationship between the volume of the used diluent and the LC-50 value showed an inverse correlation as a single straight line. In any series of the experiments, 4ml application has given the most stable LC-50 value. The absolute amount of the active ingredient will be expressed as an index which is obtained by the product of the volume of diluent at each dilution and the concentration. Experiments showed that the more the volume of diluent at each dilution was used, the more the mortality was determined even when the index value was constant. It seems to be influenced by the additional drowning effect. On the contrary, in case of the 1ml application the mortality decidedly decreases. An explanation of this phenomenon will be reported elsewhere.