Effect of temperature on the larvicidal activity of Bacillus thuringiensis product against several lepidopterous insects in a laboratory test and factors affecting the results
2007
Asano, S.
Influence of environmental temperature (15, 20, 25 or 30℃) on the larvicidal activity of Bacillus thuringiensis (Bt) in a laboratory test was investigated using a diet incorporation method against four lepidopterous insects, the diamondback moth, Plutella xylostella, the smaller tea tortrix, Adoxophyes honmai, the cabbage armyworm, Mamestra brassicae, and the common cutworm, Spodoptera litura. Both of exposure periods and reading times affected the results, although they were not similar among insect species and temperatures. The longer exposure and later reading time usually caused the higher mortality, especially under low or high temperature. The low or high temperature reduced severely the larval development for certain insect species. When temperature is unsuitable for normal development of test insect it resulted to show higher susceptibility to Bt. Therefore effect of temperature on the larvicidal activity of Bt in a laboratory test seems different among insect species and the susceptibility to Bt should be evaluated by considering test conditions which minimize the influence affecting the results. The present study suggests that effect of temperature on the larvicidal activity of Bt against four lepidopterous insects is not serious, as long as the test is carried within the range where normal larval develo-pment can achieve.
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