Lethal and sublethal effects of two new insecticides spirotetramat and flupyradifurone in comparison to conventional insecticide deltamethrin on Trichogramma evanescens (Hymenoptera: Trichogrammatidae)

The effects of three insecticides including deltamethrin, spirotetramat and flupyradifurone on pre-imaginal stages of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) were investigated using dipping method. The mean emergence rate of T. evanescens when exposed to the recommended field concentrations of deltamethrin, spirotetramat and flupyradifurone were 62.8, 84 and 86.1%, respectively while 94.3% of the wasps emerged in the control group. According to the concentration-response experiments, the LC50, values of deltamethrin, spirotetramat and flupyradifurone were 262.9, 274.8 and 334.8 ppm, respectively. The results indicated that lethal (LC50) and sublethal (LC30) concentrations of three tested insecticides significantly reduced the fecundity and longevity of T. evanescens. However, LC30, of spirotetramat and flupyradifurone didn't influence the oviposition duration of the wasps when compared with the control group. The gross reproductive rate (GRR), intrinsic rates of increases (r), net reproductive rate (R-0), and finite rate of increase (lambda) were significantly lower in all the treated wasps in comparison with control. However, the mean generation time (T) was not affected by the sublethal concentrations of tested insecticides. According to our findings, all insecticidal treatments have adverse effects on the population of T. evanescens, notwithstanding sublethal concentration of flupyradifurone followed by spirotetramat were more compatible with adults T. evanescens in comparison with deltamethrin. However, further studies under the field conditions are required to confirm the results.