The fitness of Helicoverpa armigera (Hübner) was determined using demographic studies on the F1 generation that survived after exposure to four sublethal doses (LC50, LC30, LC20 and LC10) of imidacloprid. The effects were assessed on the surviving individuals emerged from sixth-instar larvae that had ingested imidacloprid-treated chickpea pods. Age-specific parameters were found to be highest with the commencement of age and gradually decreased with the progression of age in both the treated and non-treated groups. Survivorship was reduced to 37 days after exposure to the sublethal dose of LC50 when compared with 42 days in groups not exposed to the insecticide. The highest number (17%) of unhatched eggs was recorded in insects treated with the LC50 dose of imidacloprid, whereas 98% of the eggs hatched in the unexposed group. The potential fecundity of the F1 generation females was reduced to 330 eggs/female/generation when treated with the LC50 dose compared with that of the unexposed females. The intrinsic rate of increase was found to be least in insects exposed to the LC20 dose (0.0355 females/female/day) and highest (0.0470) in the unexposed group. It took 38.83 days for H. armigera to complete one generation in the unexposed population, while this was reduced to 33.94 days after exposure to the sublethal dose of LC50. The longevity of adults decreased when the larvae were exposed to the sublethal dose of imidacloprid. The developmental time of pre-pupae and pupae significantly decreased and was least when exposed to the highest sublethal dose of the insecticide. Thus, at sublethal doses, imidacloprid caused a significant reduction in the survival and fecundity as well as increased mortality of H. armigera in the subsequent generation after exposure to the insecticide. In conclusion, imidacloprid can be successfully incorporated into integrated pest management of H. armigera.

In the literature, various environmental factors are described as being capable of influencing the reproductive output of insect females irrespective of their body size. Still, female body size or weight is widely used as a proxy for fecundity. In the present study, a seven-year data set on the autumnal moth, Epirrita autumnata (Borkhausen) (Lepidoptera: Geometridae), was used to analyze whether the body weight-fecundity relationship in this capital breeding, cyclic forest defoliating lepidopteran is constant across years. Ambient temperature conditions and density of conspecifics during larval development, the length of the pupal period, as well as moth densities in the parent generation were examined as factors capable of modifying the body weight-fecundity relationship. While the regression slope of potential fecundity (total egg numbers per female) on pupal mass was constant across years, the mean total egg number per given body weight (the regression intercept) was significantly different between years. This residual variance in egg numbers after controlling for the effect of pupal mass was best explained by the pooled geometrid density (autumnal and winter moths) in the parent generation. The total egg number per given body weight decreased with increasing density of geometrid moths in the parent generation. Thus, maternal density effects on offspring fecundity were found in this system. Their rather weak nature suggests, however, that this maternal effect alone does not have the potential of causing cyclic population dynamics in the autumnal moth.