Proteus, Matrine, and Pyridalyl Toxicity and Their Sublethal Effects on Orius laevigatus (Hemiptera: Anthocoridae)

Proteus, matrine, and pyridalyl were tested in the laboratory for their effects upon Orius laevigatus (Fieber), which is a polyphagous predator used for IPM programs of Frankliniella occidentalis (Pergande). Against female adults, the most toxic insecticide was Proteus (LC50 = 44.3 µl L-1), followed by pyridalyl (LC50 = 83.8 µl L-1) and matrine (LC50 = 102.7 µl L-1). The mortality of female adults was checked 24, 48, 72, and 96 h after exposure to 14-d residues of the treatments on strawberry leaves. The residual of Proteus was less toxic; the remaining products caused the lowest mortality at different times after exposure. Sublethal treatments (LC25) significantly prolonged the developmental duration of total immature stages from 17.6 d in control to 21.6 and 20.0 d in Proteus and pyridalyl treatments, respectively. Also, the fecundity of O. laevigatus treated with Proteus, pyridalyl, and matrine decreased to 58.8%, 75.6%, and 96.7%, respectively, in comparison to the control. Compared with the control population (0.118 d-1), the intrinsic rate of increase (r) of F1 generation decreased by 0.053, 0.095, and 0.110 d-1 in Proteus, pyridalyl, and matrine treatments, respectively. The consumption rate of control bugs reached 14.0 thrips during 24 h. The adults fed on Proteus treatment had the lowest consumption rate in this period (9.4 preys). Overall, matrine proved to be harmless with reproductive capacity and r similar to what was recorded in control bugs. We concluded that matrine can be used as an alternative for the synthetic insecticide to integrate with O. laevigatus.