Effects of three insecticides on adult bionomics of the parasitoid Encarsia formosa

Abstract

Pesticides can negatively affect many life history traits of natural enemies. In this study, we studied the effects of three insecticides with different modes of action on the bionomics of Encarsia formosa, a parasitoid of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Buprofezin (800 mg (a.i.)/L) and pyriproxyfen (50 mg (a.i.)/L) were selected among IGRs, while fenpropathrin (250 mg (a.i.)/L) was selected from the Pyrotheroids. Adults of E. formosa were treated via exposure to residues of insecticides on leaf discs. Our results revealed that buprofezin and pyriproxyfen did not affect longevity and fecundity, while fenpropathrin significantly reduced the longevity and fecundity of treated wasps. Results of logistic regression revealed that control, buprofezin- and pryproxyphen-treated E. formosa was a function of host density and followed a type II functional response. In contrast, E. formosa treated by fenpropathrin showed a type III functional response. Estimated attack rate for buprofezin and pyriproxyfen did not differ significantly from the control, whereas fenpropathrin-treated wasps showed a lower attack rate than the control. According to the obtained results, handling time of fenpropathrin-treated wasps was significantly higher (4.57 ± 0.5) than the control (2.83 ± 0.35). Our results showed that the maximum parasitism rate achieved by control wasps was 8.39, while the rate for buprofezin-, pyriproxyfen- and fenpropathrin-treated wasps was 6.99, 7.69 and 5.25, respectively. Overall, results suggest that buprofezin and pyriproxyfen can be used in an integrated pest management programme or biological control programme without destructive effects on the efficiency of this natural enemy in green houses.