The effect of Tetranychus turkestani and Eutetranychus orientalis (Acari: Tetranychidae) on the development and reproduction of Stethorus gilvifrons (Coleoptera: Coccinellidae)

Abstract

Stethorus gilvifrons Mulsant, native to the Mediterranean region, is often observed feeding on Tetranychus turkestani Ugarov & Nycolsky and Eutetranychus orientalis Klein on different host crops. Fecundity of S. gilvifrons on T. turkestani and E. orientalis was evaluated by placing newly emerged pairs on leaf discs infested with different developmental stages of T. turkestani or E. orientalis. They were maintained at 30 °C and changed daily until death of the female. Adult female mean longevity was 58 days on T. turkestani and 45 days on E. orientalis. Mean fecundity was 175 eggs per female on T. turkestani and 318 eggs per female on E. orientalis. No significant differences were detected in the duration of life stages between T. turkestani and E. orientalis. Mean preimaginal mortality was 20% on T. turkestani and 24% on E. orientalis, with no statistical differences. Mean generation time ( T) was 26.76 and 22.83 days on T. turkestani and E. orientalis, respectively. Net reproductive rate ( R o) was significantly greater on E. orientalis (154.08) than on T. turkestani (97.6), but the estimate of intrinsic rate of increase ( r m) was not statistically different (0.221 and 0.171, respectively). Our results suggest that both T. turkestani and E. orientalis are essential prey for S. gilvifrons development and reproduction and that E. orientalis is slightly more suitable than T. turkestani.