شاخص‌های رشد جمعیت کفشدوزک شکارگر Exochomus nigripennis (Erichson) (Col.: Coccinellidae) با تغذیه روی شته جالیز Aphis gossypii (Glover) (Hemi.: Aphididae)

Aphis gossypii (Glover) (Hemi.: Aphididae) is a polyphagous aphid distributed nearly world-wide, vectors many viruses and is an important pest of various crops. The ladybird, Exochomus nigripennis (Erichson) (Col.: Coccinellidae) has been reported from different countries in the world, and is also a common predator in horticultural and forestry systems of Iran. A high predatory rate and the possibility of mass rearing of E. nigripennis make it a potential candidate for classical biological control. The population growth parameters such as the intrinsic rate of increase (r) are suitable tools for describing the growth potential of a population under prevailing climatic and feeding conditions, as a reflection of the overall effects of temperature and food on the population’s development, reproduction, and survival characteristics. In this study, the population growth parameters of E. nigripennis feeding on A. gossypii were determined at 25±1°C, with 16:8 h L: D, at an average daily relative air humidity of 60±10% on cucumber leaves. The means and standard errors of the fecundity, oviposition period and population growth parameters were estimated using the bootstrap procedure. According to the obtained results, the oviposition period of females was 31.77 days; also the mean fecundity per female was 381.23 eggs. Although the number of produced females offspring was higher than males (58% female), no significant difference was observed with the expected ratio of 1:1 (χ2= 0.413; df= 1, P >0.05). The intrinsic rate of increase (r) was 0.099 ± 0.003 day−1. The finite rate of increase (λ) was 1.105 ± 0.003 day−1. Gross reproduction rate (GRR) and net reproductive rate (R0) values were 341.21 ± 34.41 and 185.85 ± 25.46 female’s offspring, respectively. The mean generation time (T) was 52.45 ± 0.61 days. Our findings suggest that E. nigripennis can successfully complete its life cycle on A. gossypii and have excellent potential for biological control agent of this pest species.