Influence of temperature on the biological activity of insecticides in soil.

Abstract

A study was conducted to determine the extent to which temperature influences the biological activity of insecticides in soil. First instars of the common field cricket, Acheta pennsylvanicus (Burmeister), were used as test insects. Tests were conducted in controlled environmental chambers at 15, 21, 27, and 33°C. Temperature had no effect on the toxicity of aldrin and heptachlor applied directly to the test insects, but DDT exhibited a negative temperature coefficient. The toxicity of aldrin and heptachlor was positively correlated with temperature as residual contact poisons applied to a glass surface, DDT exhibited a positive temperature coefficient between 15 and 21°C but was negatively correlated at higher temperatures. In moist and dry sandy loam and moist muck soils, aldrin and heptachlor showed positive temperature coefficients with the most pronounced differences occurring in the dry sandy loam. The toxicity of DDT was negatively correlated with temperature in the moist soils, but temperature had little effect on its activity in dry sandy loam. Diazinon, Dursban® ( O,O -diethyl O -(3,5,6-trichloro-2-pyridyl) phosphorothioate), and methomyl all had positive temperature coefficients in moist sandy loam. The results are discussed in relation to the effect of temperature on insect mobility, insecticide volatilization, and adsorption of insecticides by soil.