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.
The western flower thrips (WFT), Frankliniella occidentalis (Pergande) is one of the most harmful pests of crops in greenhouses and fields. Considering the need for studies that introduce new insecticides for control of the WFT, the leaf dip method was carried out to study the acute toxicity of Proteus, matrine, and pyridalyl to adult thrips, and life tables were constructed to assess the impacts of sublethal concentrations (LC25) of these insecticides on the development and reproduction of the F1 generation. Bioassays showed that the toxicity of matrine (LC50: 45.9 µl ml–1) and Proteus (LC50: 54.5 µl ml–1) was higher than pyridalyl (LC50: 176.5 µl ml–1). At LC25 concentration, both Proteus and matrine prolonged the development period and reduced the survival rate of eggs, larval stages, and pupae in the F1 generation. Also, the adults’ longevity, oviposition duration, and the cumulative number of eggs laid per female (fecundity) were decreased significantly. Sublethal concentrations of Proteus and matrine inhibited the population growth rate relative to the control based on the predicted number of offspring. The lowest net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were estimated for Proteus (7.02 offspring/individual, 0. 0838 d–1, and 1. 08 d–1, respectively). In contrast, the WFT F1 generation that resulted from parent adults treated with pyridalyl was neither affected in their developmental time, nor fecundity, or the intrinsic rate of increase. According to our findings, all tested insecticides, especially Proteus, showed good potential for use in integrated pest management strategies against F. occidentalis.
The predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) is an effective biological control agent that suppresses populations of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) under greenhouse conditions. Our study assessed the lethal and sublethal effects of three novel pesticides on this predator. Results showed that pyridalyl presented the highest toxicity against A. swirskii adults based on LC50 (41.7 mg L-1). Also, sublethal concentrations (LC25) of Proteus® and pyridalyl not only significantly prolonged the duration of A. swirskii immature stages but alsoreduced the fecundity of the predator female adults by 21.4 and 41.5%, respectively. Similarly, the LC25 of both pesticides significantly reduced life table parameters of the F1 generation, which are important in the effective control of F. occidentalis, particularly in conservation biological control. In contrast, the LC25 of matrine stimulated reproduction in A. swirskii populations by significantly increasingR0 and r. Within a 24-h period, the number of F. occidentalis consumed by A. swirskii adults exposed to fresh Proteus® and pyridalyl residues was reduced by 35.6% and 15.8%, respectively. Proteus® caused the highest mortality in persistence assessments up to 96h. Our results indicated that only matrine is marginally compatible with the use of A. swirskii.
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