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The tomato leaf miner, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae), is one of the most important pests causing significant economic losses in plant species belongingthe Solanaceae family. The preferred management method for T. absoluta currently involves insecticide application. However, beside the undesired effects of insecticides, chemical treatments can also negatively impact the efficiency of integrated pest management programs (IPM). Bacillus thuringiensis (Shigetane 1902) (Bacillales: Bacillaceae) (Bt) is a pathogen with formulations used as host-specific bioinsecticides. These formulations decompose quickly in the environment, thereby reducing non-target effects and residue problems compared to chemical pesticides. In this study, the effectiveness of six commercial Bt products, belonging to aizawai and kurstaki strains, against T. absoluta was assessed under laboratory conditions, using manufacturer-recommended doses. The efficacy of the Bt products varied between 70 and 97.5%. The lowest and highest mortalities were recorded in B. thuringiensis var. aizawai and B. thuringiensis var. kurstaki products, respectively. Mortality reached 100% within three days following insecticide treatments, whereas peak mortality in Bt applications was noted after a post-treatment period of fifteen days. These findings highlight the potential of certain Bt products as effective components of IPM programs for T. absoluta, suggesting the need for further field studies to optimize their use in agricultural practices.

 

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Tuta absoluta(Meyrick) is a serious pest of tomato throughout the world. The life history and the life table parameters of T. absolutawere studied on 12 different commercial tomato cultivars. The longest larval developmental period (12.92 ± 0.11 days), the longest total developmental time (26.20 ± 0.22 days), the longest total pre-oviposition period (29.31 ± 0.63 days) and the shortest oviposition period (5.08 ± 0.43 days) were recorded on Korral cultivar. The highest pupal mortality was found on Korral (23.53%) and the lowest larval and pupal growth indices were observed on Korral (6.57and 8.87, respectively). The highest and the lowest overall mortalities were observed on Korral (35.00%) and on Valouro (21.67%), respectively. The lowest and the highest intrinsic rate of increase (r_m) were found on Korral (0.1046 ± 0.0005 day^-1) and on Valouro (0.1584 ± 0.0002 day^-1) cultivars. Also the lowest finite rate of increase (λ) (1.1102 day^-1) and the highest doubling time (6.63 days) of the tomato leafminer were observed on Korral cultivar. Therefore, it was concluded that among the 12 tomato cultivars that were studied in this research, Korral was relatively unsuitable to T. absolutaand can be used in the integrated control programs (IPM) of this pest.

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The tomato leaf miner, Tuta absoluta (Meyrick) is an imported pest and serious threat to tomato production in farms and greenhouses of Iran. Use of genetically engineered plants expressingcarbohydrase inhibitors is one of the non-chemical methods for controlling insect pests, and knowledge about enzymatic properties of carbohydrases will help us to achieve this goal. Therefore, in present study we characterized biochemical properties of digestive carbohydrases in the midgut of last larval instar of T. absoluta fed on different tomato cultivars (Kingston, Riogrande, Super Luna, Super Chief, Super strain B and Calj). While the highest amylolytic activity was on Super strain B, the lowest was on Super Chief. The optimal pH and temperature for α-amylase were found to be at pH 9.0 and 45 °C, respectively. As calculated from Lineweaver-Burk plots, the highest Km and Vmax values for α-amylase obtained in Super Chief and Super Luna cultivars were 0.565 ± 0.11mM and 2.287 ± 0.4mM/min, respectively. The effects of different compounds on amylolytic activity indicated that CaCl2, MgCl2, NaCl and KCl increased amylase activity, whereas EDTA, ZnCl2 and BaCl2 decreased the enzyme activity in Super Luna cultivar. The highest activity of α-/ß-glucosidases was observed at pH 6.0 and 7.0, respectively, whereas the optimal pH for α/ß-galactosidases was at 5.0. The highest specific activity of α-/ß-glucosidases was determined in Riogrande-fed larvae, whereas the highest α/ß-galactosidases activity was in the larvae fed on Riogrande and Calj cultivars, respectively. By the native- PAGE, two bands were clearly detected for α-amylase. Since the larvae reared on Kingston showed lowest carbohydrase activities, this cultivar could possibly be suggested as the least suitable host for feeding of T. absoluta.

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The effects of four insecticides, abamectin (1500 and 750mgl^-1), emamectin benzoate (1000 and 500mgl^-1), acetamiprid (500 and 250mgl^-1), and flubendiamide (500 and 250mgl^-1), were studied on different preimaginal stages of T. brassicae and T. evanescens, the egg parasitoids of tomato leaf miner Tuta absoluta (Lepidoptera: Gelechiidae). Parasitized eggs of the Angoumois grain moth Sitotroga cerealella (Lepidoptera: Gelechiidae) were treated by the dipping method at the larval, prepupal, and pupal stages of the parasitoid. For persistence evaluation, the insecticides were applied at the recommended concentration on tomato plants by a hand sprayer till runoff point. Plants were maintained under a transparent polyethylene rain cover in the field. Leaves of the treated tomato plants were sampled and transferred to the laboratory at time intervals of 3, 5, 16, and 31 days after application. Based on our study, abamectin was the most harmful insecticide for immature stages of both parasitoids T. brassicae and T. evanescence. Treatment by abamectin at the pupal stage had more adverse effects compared to prepupal or larval stages. Acetamiprid with 30.5% and 31.6% mortality in less than five days was classified as the short-lived insecticide for T. brassicae and T. evanescens, respectively. The same result was obtained in flubendiamide treatment which caused 27.2% and 26.1% mortality to the parasitoids, respectively. Abamectin with 16.1% and 13.8% mortality in less than 16 days was slightly persistent. However, emamectin benzoate with 13.3% and 15.5% mortality in less than 30 days was classified as moderately persistent for those two species, respectively. Therefore, flubendiamide and acetamiprid were non-harmful to both T. brassicae and T. evanescence wasps and are good candidates to be incorporated into IPM programs in combination with biological agents for the control of tomato leaf miner T. absoluta. By contrast, emamectin and abamectin should be used with greater care as a part of an IPM procedure.

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Stenomesius japonicus (Ashmead, 1904) (Hymenoptera: Eulophidae) was collected for the first time from larvae of the tomato leaf-miner, Tuta absoluta (Meyrick, 1917) (Lepidoptera: Gelechiidae) infesting Lycopersicon esculentum Mill. in Syria. Diagnostic morphological characters, biology and distribution of the newly recorded species are provided. Its role in the biological or integrated control of T. absoluta remains to be evaluated. A list of all eulophid wasps recorded from Syria is also provided.

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The tomato leafminer, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) is one of the most damaging tomato pests in the world and in Iran. The toxicity of acetamiprid, eforia (thiamethoxam + lambda-cyhalothrin) and hexaflumuron alone and in mixture with emamectin benzoate was studied against 4^th-instars of Tuta absoluta (Meyrick) at 25 ± 2 °C, 65 ± 5% RH and 16:8 (L:D) h. Moreover, the mixtures of examined insecticides with emamectin benzoate at LC₁₅:LC₁₅ ratio were assessed on the general esterase enzyme activity and total protein content of 4^th-instars. The highest toxicity was found for emamectin benzoate after 72 h (LC₅₀ = 0.48 mg a.i./l), followed by acetamiprid (LC₅₀ = 46.94 mg a.i./l), eforia (LC₅₀ = 156.24 mg a.i/l) and hexaflumuron (LC₅₀ = 670.32 mg a.i/l). Mixing emamectin benzoate with acetamiprid at the ratio of LC₅₀:LC₅₀ and LC₂₅:LC₂₅ resulted in synergistic impacts while mix of two other ratios of the same pesticides represented additive influences. The mixture of emamectin benzoate with either hexaflumuron or eforia at all ratios created antagonistic and additive effects, respectively. Mixing emamectin benzoate with either acetamiprid or eforia increased larval esterase activity, however, there was no significant difference between emamectin benzoate in mixture with hexaflumuron and using it alone. Mixing emamectin benzoate with the examined insecticides considerably decreased the larval total protein content. Based on the findings of this work, the mixtures of eforia and acetamiprid with emamectin benzoate represented greater negative effects against 4^th-instars compared to emamectin benzoate alone and the control.
 

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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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 Tomatoes are an important vegetable crop in different parts of the world, where they are grown year-round. Currently, the most important problem facing tomato growers in the world is the devastating damage caused by the invasive tomato leaf miner, Tuta absoluta Meyrick (Gelechiidae: Lepidoptera). In this study, the efficacy of three bioinsecticides (Bacillus thuringiensis formulations, spinosad and emamectin benzoate, and two chemical insecticides (indoxacarb and chlorpyrifos) against T. absoluta and their adverse effects on predators were conducted in two different governorates in Egypt, based on recommended doses of the tested insecticides. In addition, the residue dissipation of the tested insecticides was determined in tomato fruits. Results indicated that emamectin benzoate was the most effective insecticide, exhibiting the highest reduction in T. absoluta density of 78.05 and 87.11% in Giza and Qualybia governorates, respectively, followed by indoxacarb (77.01%) in Giza and spinosad (80.44%) in Qualybia. In addition, our finding proved that the tested biopesticide formulations, especially Bt formulations, are environmentally friendly to two of the most important predators in tomato cultivation: Nesidiocoris tenuis and Macrolophus pygmaeus Reuter. Moreover, the analysis of insecticide residues on tomato fruits revealed that bioinsecticide residues dissipated faster than conventional insecticide (chlorpyrifos). The results of this research suggested that bioinsecticides could be used for the management of T. absoluta under field conditions.