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.

Lethal and Sublethal Effects of Proteus, Matrine, and Pyridalyl on Frankliniella occidentalis (Thysanoptera: Thripidae).

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.

Prey-Stage Preference and Comparing Reproductive Performance of Aphidoletes aphidimyza (Diptera: Ceccidomyiidae) Feeding on Aphis gossypii (Hemiptera: Aphididae) and Myzus persicae.

The predacious midge, Aphidoletes aphidimyza (Rondani), is an effective exclusive natural enemy of aphids in greenhouses and field crops. In this study, prey preference of A. aphidimyza was determined using seven treatments including different stages (third-instar nymphs and adults) of two prey species (Aphis gossypii Glover and Myzus persicae (Sulzer)) based on Manly's ß preference index. Results of experiments consisting of two different preys showed that A. aphidimyza larvae consumed A. gossypii more than M. persicae, and the third nymphal stage of both species was preferred more, compared with adults. When all four types of prey were studied, Manly's index was 0.379, 0.235, 0.208, and 0.176 for nymphs of A. gossypii and M. persicae and adults of A. gossypii and M. persicae, respectively. Therefore, the nymphs of both species, as the most preferred prey, were used to study the reproductive performance of the predator in microcosm conditions. The significantly longer adult longevity (female: 7.62 ± 0.15, male: 7.42 ± 0.23 d), higher fecundity (93.75 ± 2.94 offspring per female), and higher intrinsic rate of increase (0.175 ± 0.009 d-1) of A. aphidimyza were obtained, while consuming third-instar nymphs of A. gossypii. Finally, this study indicated that third-instar nymphs of A. gossypii are the most suitable food for mass rearing of A. aphidimyza.

Effect of temperature on life history of Aphidius colemani and Aphidius matricariae (Hymenoptera: Braconidae), two parasitoids of Aphis gossypii and Myzus persicae (Homoptera: Aphididae).

The performance of two aphid parasitoids, Aphidius colemani Viereck and Aphidius matricariae (Haliday), against Aphis gossypii Glover on greenhouse cucumber (Cucumis sativus L.) and Myzus persicae (Sulzer) on sweet pepper (Capsicum annuum L.) were evaluated at various constant temperatures. Biological parameters of both parasitoids including developmental time, pupal survivorship, percentage of parasitism, and sex ratio of the progeny were studied at 5, 10, 15, 20, 25, 30, and 35 degrees C. At 25 degrees C, an average of 10.0 +/- 1.1 and 9.8 +/- 1.1 d was needed for A. colemani to complete its development from oviposition to adult eclosion on A. gossypii and M. persicae, respectively. The corresponding average times needed for A. matricariae were 11.9 +/- 0.9 and 11.5 +/- 1.1 d, respectively. The lower developmental thresholds for A. colemani reared on A. gossypii and M. persicae were estimated from linear regression equations to be 2.97 and 2.65 degrees C, respectively, whereas these values for A. matricariae were 3.37 and 3.51 degrees C, respectively. Parasitization rate of both parasitoid species, recorded as percent aphids mummified, increased almost linearly with increasing temperature to reach a maximum at 25 degrees C and decreased at 30 degrees C. The optimal temperatures for development of A. colemani and A. matricariae were approximately 30 and 25 degrees C, respectively, and high mortality occurred at higher temperatures. The Lactin 2 and Briere 1 developmental models were accepted based on their excellent goodness-of-fit to the data (residual sum of square and coefficient of determination) and estimable temperature thresholds and are strongly recommended for the description of temperature-dependent development of A. colemani and A. matricariae.

Thermal requirement and development of Liriomyza sativae (Diptera: Agromyzidae) on cucumber.

The effect of temperature on developmental rate of vegetable leafminer, Liriomyza sativae Blanchard (Diptera: Agromyzidae), was determined at seven constant temperatures (10, 15, 20, 25, 30, 35, and 40 degrees C) on cucumber, Cucumis sativus L. 'Negin'. The total developmental period (oviposition to adult emergence) decreased with increasing temperature, although no development occurred at 10 and 40 degrees C. Using the linear model, the estimated lower temperature threshold for the egg, larval, pupal, and entire developmental period was 9.20, 9.75. 11.01, and 10.20 degrees C and the effective accumulative temperatures for these stages were 64.10, 81.97, 106.38, and 250 degree-days (DD), respectively. Data also were fitted to nonlinear temperature-dependent models. Evaluation of the models was based on fit to data, number and biological value of the fitted coefficient, number of measurable parameters, and accuracy of the estimation of the thresholds. Conclusively, linear and Briere models are recommended as the most efficient for the description of temperature-dependent development of L. sativae. Temperature-based developmental data can be used to predict occurrence, number of generations, and possibly population dynamics.