Development and reproduction of a potential biological control agent, Aphelinus varipes (Hymenoptera: Aphelinidae), at different temperatures

Abstract

The development and reproductive potential of an indigenous parasitoid, Aphelinus varipes (Forster), was studied at 15, 17, 20, 25, and 30 °C. Developmental durations decreased with increasing temperatures. The emergence rate was higher than 90 % at 15, 17, and 20 °C. Offspring sex ratios were 0.69, 0.54, and 0.70 at 17, 20, and 25 °C, respectively, but were 0.14 at 15 °C and 0.38 at 30 °C. Developmental zeros of females and males were calculated as 9.9 and 9.6 °C, respectively. The effective accumulative temperature (K) was 204.1 degree-days in both sexes. Fecundity peaked in early age after emergence, then gradually decreased in a fluctuating manner at 20 and 25 °C. Host feeding continued constantly during the life of female adults at two temperatures. Single female parasitoids produced 218.5 and 203.1 mummies at 20 and 25 °C, respectively, during their lifespans. Aphids killed by parasitoid host feeding numbered 79.1 at 20 °C and 63.8 at 25 °C. Longevities were 27.0 days at 20 °C and 20.6 days at 25 °C. Moreover, intrinsic rates of natural increase (r m) were estimated as 0.151 at 20 °C and 0.227 at 25 °C. We discuss the potential of A. varipes as biological control agents by comparing them with Aphidius colemani Viereck, which has been introduced to horticultural crops in greenhouses in Japan.