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For successful implementation of integrated pest management (IPM) programs, having knowledge on lethal and low-lethal effects of pesticides on natural enemies is necessary. The present study evaluated the low-lethal effect of thiamethoxam on life table parameters of the subsequent generation of the predatory mite, Neoseiulus californicus McGregor (Acari: Phytoseiidae) fed on Tetranychus urticae Koch under laboratory conditions. The low-lethal concentrations LC₅, LC₁₀ and LC₂₀ were determined based on a dose-effect assay. The raw data were analyzed based on age-stage two sex life table analysis. Exposure to the low-lethal concentrations of thiamethoxam had no significant effects on developmental time of offspring of treated mites. Compared with control treatment, the oviposition period of treated mites with LC₅, LC₁₀ and LC₂₀ decreased significantly. The highest and lowest values of total fecundity were obtained at control (35.3 eggs/female/day) and LC₂₀ (23.6 eggs /female/day), respectively. The net reproductive rate (R₀) decreased with increasing dose from LC₅ (22.6 offspring) to LC₂₀ (15.0 offspring). The intrinsic rate of increase (r) and finite rate of increase (λ), were not affected by increasing concentrations. The mean generation time (T) decreased significantly at upper dose (LC₂₀ = 13.2 d), compared with control (14.7 d). In consequence, the low-lethal concentration influences of thiamethoxam in combination with N. californicus in order to design management programs of T. urticae are discussed.
 

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The two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) is one of the most important pests of many crops worldwide. Combined tactics for pest management have a significant special effect on reducing pesticide use and maintaining the activity of natural enemies, which is the main objective of IPM programs. The effect of low-lethal concentrations of Eforia (24.7 SC, Syngenta Co.) at LC₅, LC₁₅, and LC₂₅ were investigated on biological parameters of Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) under laboratory condition at 25 ± 1 °C, 70 ± 5% RH and 16:8 (L: D) h. The data were analyzed based on a two-sex life table procedure. The results showed that Eforia caused a significant reduction in fecundity (Control: 37.17; LC₂₅: 23.04 eggs/female) and total life span (Control: 42.67 days; LC₂₅: 24.65 days). The net reproductive rate (R₀) was 22.31, 20.12, 15.14, and 14.98 eggs/individual, respectively, at control, LC₅, LC₁₅, and LC₂₅. The maximum and minimum values for the intrinsic rate of increase (r) were recorded to be 0.17 (Control, LC_5, and LC₂₅) and 0.15 (LC₁₅) day^-1 for the treated mites. Based on the results, the application of low lethal concentrations of Eforia harms some biological parameters of this predatory mite, and the results of this study showed that Eforia may not be applied for the control of T. urticae pest together with A. swirskii.

 

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Abstract: Soil reinforcement is one of the soil improvement techniques. Over the last four decades, a large number of researches have been carried out in order to obtain the reinforcement type and the bearing capacity improvement of the reinforced soil. A new reinforcement type called Grid-Anchor (G-A) has been recently invented which is made of geogrids by adding polymer anchors to it. In this study the bearing capacity of ring and circular footings located on granular soils reinforced with the G-A is investigated using numerical analyses. Commercial finite-element software PLAXIS is employed to perform the simulations. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance that anchors are effective, for each foundation were investigated. The effect of reinforcement stiffness for two types of footing has been investigated. A comparison between the results obtained for the G-A and geogrid reinforcement systems and unreinforced soils is demonstrated as well. Abstract: Soil reinforcement is one of the soil improvement techniques. Over the last four decades, a large number of researches have been carried out in order to obtain the reinforcement type and the bearing capacity improvement of the reinforced soil. A new reinforcement type called Grid-Anchor (G-A) has been recently invented which is made of geogrids by adding polymer anchors to it. In this study the bearing capacity of ring and circular footings located on granular soils reinforced with the G-A is investigated using numerical analyses. Commercial finite-element software PLAXIS is employed to perform the simulations. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance that anchors are effective, for each foundation were investigated. The effect of reinforcement stiffness for two types of footing has been investigated. A comparison between the results obtained for the G-A and geogrid reinforcement systems and unreinforced soils is demonstrated as well. Abstract: Soil reinforcement is one of the soil improvement techniques. Over the last four decades, a large number of researches have been carried out in order to obtain the reinforcement type and the bearing capacity improvement of the reinforced soil. A new reinforcement type called Grid-Anchor (G-A) has been recently invented which is made of geogrids by adding polymer anchors to it. In this study the bearing capacity of ring and circular footings located on granular soils reinforced with the G-A is investigated using numerical analyses. Commercial finite-element software PLAXIS is employed to perform the simulations. The effect of depth of the first reinforcement layer, the vertical spacing, the number and width of reinforcement layers, the distance that anchors are effective, for each foundation were investigated. The effect of reinforcement stiffness for two types of footing has been investigated. A comparison between the results obtained for the G-A and geogrid reinforcement systems and unreinforced soils is demonstrated as well

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This paper explores the empirical evidence of the nature of intra-metropolitan supply linkages and industrial clustering and searches for the driving forces that enhances the learning processes and innovation capacities hence; contributing to competitive advantage within the Tehran metropolitan. The research points to accelerating growth in the automotive sector since the late 1980s and early 1990s which has been the driving force of the Tehran’s economy. This growth appears to be related to industrial clustering and systemic linkages with actors such as suppliers, sub-contractors and so on. The analysis of empirical evidences from the sample industrial cluster indicates a considerable number of interesting findings from strong degrees of industrial clustering. However, there are some weak evidences of industrial clustering such as weak institutional environment in the cluster.

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Cabbage aphid, Brevicoryne brassicae (L.) (Hom.: Aphididae) is an important pest of crucifers and is controlled by different insecticides, especially dimethoate.The toxicity of dimethoate in six populations of the pest from different parts of Iran was assayed using Leaf-dip method. The bioassay results indicated significant difference in susceptibility to dimethoate among the six populations that were investigated. The highest level of resistance to dimethoate was obtained for Mehrshahr (Meh) population (RR= 91.25). Diethyl maleate (DEM), ,piperonylbutoxide (PBO), and triphenyl phosphate (TPP) suppressed the level of resistance to dimethoate, indicating the resistance to this insecticide was caused by glutathione S-transferases (GSTs), mixed function oxidases, and esterases, respectively. Cytochrome P450 monooxygenases and GSTs activity increased, respectively, 2.7 and 9.6-fold in resistant population compared with the susceptible one. When α-naphthyl acetate was used as substrate, up to 4-fold increase in esterase activity was observed in resistant population. Moreover, 6.2-fold elevation in esterase activity was shown in resistant strain when β-naphthyl acetate was the substrate. Overall, the mechanisms of insecticide resistance in cabbage aphid populations from six regions of Iran were related to GSTs, esterase, and cytochrome P450 monooxygenases activities.