Effect of insecticides on the intrinsic rate of natural increase of Rhynocoris marginatus (Fabricius)

Sub-lethal concentrations of two commonly used insecticides methyl parathion (0,0009%) and endosulfan (0.0123%) on the life table parameters were evaluated in a reduviid Rhynocoris marginatus (Fabricius) in the laboratory. Both the insecticides reduced the gross as well as net reproductive rates to considerable levels. The study revealed that the values of intrinsic rate of natural increase (r_m) and finite rate of increase (X) in control insects, namely, 0.043 and 1.044 were also drastically reduced by the insecticides (0.029 and 1.029, and 0.040 and 1.04 for methyl parathion and endosulfan, respectively). Between the two insecticides, methyl parathion caused the maximum reductions in weekly multiplication rate and annual rate of increase.