Factors Affecting Residue-Film Bioassay of Insecticide Residues

Abstract

Abstract Many factors could affect the mortality of insects and bioassay results: preparation of extracts; method of preparing deposits; loss of volatile insecticides; effect of extractives and additives; age, stage, sex, weight, and species of insects; method of handling insects; size and position of test jars; food used during the test; effect of temperature, humidity, and light; exposure time; contamination of samples; interpretat i on of results; and method of calculating sensitivity. Almost all of these factors affect the mortality of insects, but only a few of them significantly interfere with the final bioassay results if a comparable series of standards is carried on side by side. To obtain more accurate results, all test jars, including the standards, should contain equal amounts of the same extractives; a corresponding standard curve should be prepared from an uncontaminated check for each series of tests; and insects used for each series of tests should be properly sampled from a mixture of several cultures. Within certain limits, the sensitivity of a bioassay may be easily increased by the manipulation of some factors, such as the volume of extract per test jar, age of test insects, size of test container, exposure time, and temperature.