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The effect of methanolic extracts of Achillea millefolium and Teucrium polium on third instar larvae of Egyptian cotton leafworm, Spodoptera littoralis were investigated. Methanolic plant extracts were mixed with artificial diet and then nutritional indices, glutathione-S transferase, esterase, α-amylase and protease, activity were measured 72h later. Approximate digestibility was increased significantly in larvae fed on the food containing methanolic extract of T. polium but there was not any significant change in insects treated with A. millefolium. T. polium significantly decreased relative growth rate (RGR), relative consumption rate (RCR), efficiency of digested food (ECD) and efficiency of conversion of ingested food (ECI) whereas A. millefolium only decreased RGR and RCR. Feeding on artificial diet containing plant extract decreased α-amylase and protease activities in the midgut of the insect. Furthermore, the effect of methanolic extract of plants on detoxifying enzymes showed that they have no effect on glutathione S-transferase and esterase activities.

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Efficacy of quercetin on α-amylase, lipase and protease activities via crustacean cardioactive peptide (CCAP) content of the midgut of the diamondback moth, Plutella xylostella (L.) was investigated. Fresh cabbage leaf discs were dipped in quercetin solution at different concentrations (100, 500 and 1000ppm) for 10 seconds. Third instar larvae of P. xylostella were fed on leaf dipped in quercetin solutions for 5 days. α-Amylase, lipase and protease activities were evaluated for 5 days. Quercetin significantly decreased lipase, protease and α-amylase activities in the midgut. The results of competitive ELISA showed that different concentration of quercetin had no effect on short neuropeptide F, tachykinin-4 and allatostatin content of the midgut, but it was shown that quercetin (500 and 1000ppm) decreased CCAP content of the midgut. Moreover, incubation of dissected midgut with CCAP increased α-amylase, lipase and protease activities. The injection of CCAP into the hemocoel clearly increased α-amylase, lipase and protease activities. Here, for the first time, it was confirmed that feeding on leaf dipped in quercetin, decreases CCAP content in the midgut of P. xylostella, that itself led to decrease of α-amylase, protease and lipase activities.
 
 

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The cotton bollworm, Helicoverpa armigera (Hübner) is an important pest of many crops. Here, effects of kaempferol on ecdysteroid titer in the ovaries, hemolymph andoocyte size via tachykinin-4 content of H.armigera were studied. Third instar larvae of H. armigera were fed on artificial diet containing different concentrations of kaempferol for 8 days. Kaempferol had insecticidal activity after 6 days. The highest level of larval mortality was approximately 36% in larvae fed diet containing 10µg/g of kaempferol for 8 days. Competitive ELISA showed that tachykinin-4 titer decreased clearly in the adult female moth's brain and hemolymph which fed on diet containing 5 and10µg/g kaempferol during their larval stage for 8 days. It also decreased ecdysteroid in the ovary and hemolymph of adult female. Moreover, oocyte size was significantly decreased. On the other hand, the injection of tachykinin-4 into the hemocoel not only increased ecdysteroid titer in the ovary but also approximately 1.4 fold increases in oocyte size was observed. In conclusion, feeding on food containing kaempferol decreased tachykinin-4 level in the brain and hemolymph that itself led to decreasing ecdysteroid titer in the ovary and hemolymph. Finally the decrease in ecdysteroid titer resulted in smaller oocytes.
 
 

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The Greenbug Schizaphis graminum (Rondani), one of the major pests of cereals, overwinter as adults and nymphs in temperate regions. The aphid population increases in early spring as the weather conditions become favorable, but it gradually decreases in mid-June as air temperature rises. Adult aphid colonies were acclimated to measure cold tolerance at 20, 15, 10, 5, and 0 °C for one week. In contrast, other colonies were acclimated to measure heat tolerance at 20, 25, and 30 °C for one week and 35 °C for two days. Then, the lowest temperature resulting in 50% mortality (LLT₅₀) and the highest temperature resulting in 50% mortality (ULT₅₀) of tested populations were defined. Moreover, changes of sugars and polyols were studied at the end of each thermal regime. The lowest LLT₅₀ was -13.2 °C at 0 °C and the highest ULT₅₀ was 40.1 °C at 35 °C. In the cold acclimation condition, glucose was the highest at 0 °C and reached to 80.9 µmol/g f.w. However, in the heat acclimation condition, the mannitol was the highest at 35 °C and reached to 43.7 µmol/g f.w. Findings indicate that high temperatures due to climate change could be a threat to aphid population size and distribution.
 

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The present study investigated the effect of allatostatin (Ast) on the adult female reproductive system of the greater wax moth, Galleria mellonella (L.). At first, different concentrations of Ast in the brain- SOG, midgut, ovaries, and fat body of 5 days old adult females were confirmed. Moreover, it was shown that the highest concentration of Ast was observed in brain-SOG. Daily injections of Ast decreased ecdysteroid concentration in the hemolymph and ovaries. Ast injection decreased the expression level of vitellogenin (Vg) genes. Furthermore, it reduced oocyte size. These results showed that Ast has a regulatory role in the reproduction of G. mellonella female.




 

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The two-spotted spider mite (TSSM) Tetranychus urticae Koch is one of the most destructive mites in many plants due to its characteristics, such as high reproductive potential, short life cycle, and feeding method. Excessive use of chemical compounds without considering environmental factors has led to high residual toxins in food products and resistance to pesticides. Temperature is an essential non-living factor that affects various biological aspects of pests and pesticide toxicity levels. In this study, the interaction of different temperatures (15, 20, 25, and 30 °C) in the photoperiod (16L:8D h) was investigated on the toxicity of spiromesifen on the adult TSSM. Then the levels of α-esterase and glutathione S-transferase activity were measured. The highest LC₅₀ was recorded at 15 °C after 24 h (LC₅₀ = 21.269 mg ai/l), and the lowest value corresponds to 30 °C after 48 h (LC₅₀ = 0.860 mg ai/l). The level of toxicity also increased with a temperature increase, so the toxicity was recorded 3.6 folds higher at 30 °C compared to 15 °C. The α-esterase and glutathione S-transferase activity also increased with an increase in the temperature, but this increase was significant only for esterase activity. The relationship between temperature and the power of pesticide toxicity in areas with different daily and controllable temperature changes can effectively provide a valuable proposal to reduce pesticide consumption and increase the efficiency of pest control.


 

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 The European grapevine moth, Lobesia botrana (Denis and Schiffermueller) (Lepidoptera: Tortricidae), is a significant pest causing economic damage to vineyards worldwide. In this research, the cold tolerance of the pupae and its relationship with diapause was investigated at 23 ± 0.5 °C, 70 ± 5% RH, and LD 12:12 h. One-day-old eggs were transferred to LD 12:12 h to induce diapause at the pupal stage. Diapausing pupae exhibited a mean supercooling point (SCP) of -24.35 °C, whereas in the non-diapausing pupae (23 ± 0.5 °C, 70 ± 5% RH, LD 16:8 h), it was -23.06 °C, with no significant difference between the two groups. Furthermore, diapausing pupae demonstrated significantly higher cold tolerance (LT₅₀ of -14.43 °C) than non-diapausing pupae (LT₅₀ of -3.33 °C). Diapausing pupae tolerated subzero temperatures without significant changes in the SCP, tolerating 11 °C lower than control pupae due to the short daylength alone. Our results suggest that the diapause state and cold hardiness of L. botrana are independent of changes after SCP, and the insect employs a freeze-intolerant strategy to overcome subzero temperatures. Cold acclimation at -5 and -10 °C for 72 h induced a significant decrease in the SCP of diapausing pupae, while a 72-h cold acclimation had no notable impact on the SCP of non-diapausing pupae. These findings provide valuable insights into the survival mechanisms of the European grapevine moth under cold conditions and diapause-related adaptations.


 

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The tomato leafminer, Tuta absoluta, is a pest that greatly harms crops. Regrettably, the application of insecticides has resulted in the emergence of resistance in the tomato leafminer. Metabolic resistance is the most prevalent form of resistance, characterized by heightened esterase activity, cytochrome P450 monooxygenase, and glutathione S-transferase enzymes encoded by specific genes. This study investigated the metabolic resistance mechanisms associated with fenvalerate resistance in the tomato leafminer and explored the genes' status. Tomato leafminer populations in Iran showed varying levels of resistance to fenvalerate; the Tehran and Urmia populations were the most resistant and sensitive, respectively. The activity level of detoxifying enzymes, particularly cytochrome P450 monooxygenase, was found to be increased in the resistant populations (i.e., Tehran) compared to the susceptible one (i.e., Urmia). Gene expression analyses showed higher transcript levels of P450, esterases, and GSTs expression levels in the resistant population compared to the susceptible population. Our findings indicated that detoxification enzymes, especially cytochrome P450 monooxygenase, and differential expression of related genes contribute to fenvalerate resistance. Identifying the specific mechanisms behind resistance could assist in pest control and resistance management programs.



 

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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.
 

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The ­antifeedant activity of nanoemulsion formulation of arugula Eruca sativa Mill. oil was studied against elm leaf beetle Xanthogaleruca luteola (Müller)(Col.:Chrysomelidae) under laboratory conditions at 25±1ºC, 75±5% RH, and LD 16:8 hours. Ingestive LC₅₀ values of the oil were studied in third instar larvae. Then, physiological parameters were evaluated following 24, 48, and 72 hours post feeding at LC₅₀ level. LC₅₀ values 24, 48 and 72 hours after application were 4.940, 3.791, and 2.938 mg mL^-1, respectively. Arugula oil at LC₅₀ level decreased the nutritional indices including efficiency of conversion of ingested food, relative growth rate, efficiency of conversion of digested food, and relative consumption rate, but increased feeding deterrence index significantly 72 hours post feeding. Nutritional reserves such as total carbohydrate, protein, and lipid contents and also digestive enzymes containing lipase, α-amylase, and protease activity were decreased showing post-ingestive toxicity. The activity of the detoxifying enzyme glutathione S-transferase was increased, indicating that this enzyme may be involved in detoxification of arugula oil, but general esterase did not change significantly. In general, it can be concluded that arugula oil possess antifeedant activity against X. luteola under laboratory condition. It seems that arugula oil has a great potential to be used as effective botanical pesticides. However, further studies such as greenhouse and field experiments are necessary before recommendation and commercialization process.

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The tomato leafminer, Tuta absoluta is a devastating invasive pest that poses a serious threat to tomato crops worldwide. Its extensive global dispersion serves its capacity to adapt to variations in climate conditions. In this context, the pupa is the most resistant stage to prolonged exposure to cold temperatures. Therefore, indicators of cold resistance were studied in overwintering pupae collected from the field and pupae reared under two constant conditions, high temperature, and long day (25°C, 16:8 L:D and 65±5% RH), and low temperature and short day (15°C, 13:11 L:D and 65±5% RH). The results show that the super cooling point (SCP) significantly decreased in December (-20.5±1.2°C) and January (-20.26±0.78°C) with a decrease in temperature. In the laboratory, the decrease in temperature and photoperiod increased the tolerance of pupae to subzero temperatures. Lethal Temperature 50 (LT₅₀) and LT₉₀ of pupae collected in the field were recorded at -13.70 to -10.23°C and -18.73 to -15.37°C, respectively. A comparison of lethal temperatures with the lowest ambient temperature in December and January indicated that T. absoluta has a high overwintering potential in Karaj, Alborz Province, Iran, and can easily survive cold winters.