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Introduction: Soil bacteria offer a promising approach to bioremediate pesticide contamination in agricultural ecosystems. This study investigated the potential of bacteria isolated from rice paddy soil for bioremediating fipronil and thiobencarb, common agricultural pesticides. Methods: Bacterial isolates capable of degrading fipronil and thiobencarb were enriched in a mineral salt medium. A response surface methodology with a Box-Behnken design was utilized to optimize pesticide degradation with the isolated bacteria. Bioaugmentation tests were performed in paddy soils with varying conditions. Results and discussion: Six strains, including single isolates and their mixture, efficiently degraded these pesticides at high concentrations (up to 800 µg/mL). Enterobacter sp., Brucella sp. (alone and combined), and a mixture of Stenotrophomonas sp., Bordetella sp., and Citrobacter sp. effectively degraded fipronil and thiobencarb, respectively. Notably, a single Pseudomonas sp. strain degraded a mixture of both pesticides. Optimal degradation conditions were identified as a slightly acidic pH (6-7), moderate pesticide concentrations (20-50 µg/mL), and a specific inoculum size. Bioaugmentation assays in real-world paddy soils (sterile/non-sterile, varying moisture) demonstrated that these bacteria significantly increased degradation rates (up to 14.15-fold for fipronil and 5.13-fold for thiobencarb). The study identifies these novel bacterial strains as promising tools for bioremediation and bioaugmentation strategies to tackle fipronil and thiobencarb contamination in paddy ecosystems. [ABSTRACT FROM AUTHOR]

Exposure to pesticides may affect the survival and normal physiological functions of the honey bee (Apis mellifera L.). The fungicide propiconazole (PRO) and the biofungicide Trichoderma are widely used in agroecosystems, and their effects on the physiology of the honey bee have been largely neglected in risk assessment procedures. We investigated the mortality and variations in physiological biomarkers of honey bee larvae and newly emerged workers exposed to PRO and Trichoderma. Exceeding the field-recommended concentrations of Trichoderma decreased the survival of newly emerged bee workers significantly through oral exposure. PRO, however, showed no significant lethal effects. Contact or oral exposure to field-realistic concentrations of PRO and Trichoderma profoundly altered the activities of detoxification, antioxidative, and digestive enzymes along with energy reserve concentrations of honey bee larvae and adult workers. Integrated biological index (IBRv2) values suggested potential risks of PRO and Trichoderma to honey bees by impairing the physiological status of larvae and newly emerged workers. [ABSTRACT FROM AUTHOR]

Podisus maculiventris (Say) is a generalist predator attacking many insect species from different orders. The bug injects saliva into its prey's body. The ingested hemolymph and liquefied internal tissues pass through the bug's alimentary tract. Collagenase working on peptide bonds of collagen and basement membrane proteins, leads to the disintegration of the prey's internal organs. As yet, there is an almost complete lack of knowledge on the collagenase activity in P. maculiventris. The collagenase activity of the salivary glands and midgut was optimum at pH 8.0 which was congruent with the optimal pH of the total proteolytic activity of the salivary glands. More collagenolytic activity was determined in the posterior lobe of the salivary glands and anterior midgut. Significant inhibition of collagenolytic activity by ethylenediaminetetraacetic acid (EDTA) revealed the enzyme is a metalloproteinase. The collagenase activity notably decreased when the bug went hungry. The salivary gland collagenase is a vital enzyme in extra-oral digestion and facilitates the action of other digestive enzymes. The midgut collagenase may be involved in the digestion of the ingested muscle fibers. The collagenase probably acts as an intoxicating agent in the saliva (venom) of P. maculiventris. Paralysing toxins are present in the salivary gland secretion.

Cacopsylla permixta and Cacopsylla bidens are major pests of pears in Iran. They are commonly sprayed with various insecticides up to 12 times a year but control by these means is no longer reliable, suggesting the evolution of resistance. Here, we report about 60‐fold variation in diazinon susceptibility both among five geographic populations of C. bidens and among three geographic populations of C. permixta, as well as 12‐ to 14‐fold variations in imidacloprid susceptibility in these populations. The levels of resistance to the two compounds were highly correlated in the different populations. Esterase, cytochrome P450, and glutathione S‐transferase activities all varied by about two‐fold among the different populations and were also highly correlated with population resistance to the two insecticides, implying differences in metabolism contribute to the differences in resistance. Bioassays with inhibitors of each class of enzyme indicated all three, but particularly the esterases, contributed to the variation in diazinon resistance, while esterase and, in particular, cytochrome P450 activities contributed to the variation in imidacloprid resistance. The most resistant populations of each species also showed some resistance to chlorpyrifos and acetamiprid, suggesting there may be wide cross resistance to organophosphates and neonicotinoids in these populations. The sampled psyllid populations showed lower levels of resistance to representatives of two other classes of insecticides currently used in Iran, spirotetramat and abamectin, though resistance to spirotetramat was detectable and was correlated with diazinon and imidacloprid resistance across populations. We conclude that metabolic resistance to a range of insecticides is now evolving in field populations of both species in Iran, warranting timely development of resistance management plans. [ABSTRACT FROM AUTHOR]

Induced host plant resistance is a potential approach to insect and disease management. Salicylic acid (SA) acts as a signal molecule to induce resistance in plants against sap-sucking insects. The effects of salicylic acid-induced resistance against common pistachio psylla, Agonoscena pistaciae Burckhardt and Lauterer, were investigated in well-watered and drought-stressed pistachio, Pistacia vera L. cv. Akbari, seedlings. Agonoscena pistaciae exhibited a significant preference for plants treated with SA as compared with untreated controls or those subjected to drought stress. Plants subjected to both drought stress and SA treatment were equivalently colonized as compared with control plants but were more attractive than those subjected to drought stress alone. Psyllid mortality increased on plants subjected to simultaneous drought stress and SA treatment as compared with controls. Salicylic acid treatment mediated production of defensive enzymes in plants, including superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), guaiacol peroxidase (GPX) and polyphenol oxidase (PPO), as well as that of other metabolites such as phenol, malondialdehyde (MDA), H2O2, free amino acids, and pigments via phenylpropanoid pathways under conditions of drought. Despite increases in activity of detoxification (glutathione S transferase, carboxylesterase) and antioxidative (SOD, CAT, APX, phenoloxidase, GPX) enzymes in psyllids, reduced survival of A. pistaciae on drought stressed and SA-treated plants was likely caused by excessive H2O2 and high phenolic content in treated plants. Based on our results, we postulate that salicylic acid-induced defense against A. pistaciae under drought conditions could be manipulated to enhance antibiosis against this key pest in pistachio orchards. [ABSTRACT FROM AUTHOR]

Despite the economic importance of pistachio very little studies have been performed on its defense physiology. Due to lack of effective method among pest management programs, pesticides, despite their known some adverse features, is the only and last option for control of pests in pistachio orchards in most cases. The present study has been conducted to determine total phenolic, total protein content, antioxidant defense response and phenylalanine ammonia-lyase activity in the leaves of pistachio seedling induced by salicylic acid (SA). Results showed that the concentrations 1 and 4 mM of SA increased the phenolic content and PAL activity. The enhanced PAL activity led to the improvement of the quantity of phenolic compounds. In addition, the SA application showed an enhancing impact on total protein content and oxidative enzymes (catalase, guaiacol peroxidase, ascorbate peroxidase, and polyphenol oxidase) activity. In all experiments the SA elicitation effect was concentration- and time-dependent. Repeated measurement statistical analysis revealed that the maximum elicitation effect of SA occurred in 3 to 9 days after the treatment. SA effects on plant defensive systems are highly complicated, and further investigations are needed to clarify the underlying mechanisms. These results can be used in designing of integrated pest management programs of pistachio pests focusing on applying safe and environment-friendly controlling methods. [ABSTRACT FROM AUTHOR]

Although Cacopsylla pyri Forster and Cacopsylla pyricola Linnaeus have long been considered as more significant pests of pear trees around the world, Cacopsylla permixta Burckhardt and Hodkinson is the most significant pest in some parts of Iran, especially in pear gardens of Karaj. Current control strategies against this pest in Iran generally involve five or six insecticide treatments each year, despite unsatisfactory results are reported at many localities. So, it is crucial to know the most susceptible generation of the pest to apply a good strategy for its control. The aim of this study was to explore the seasonal variation in susceptibility of C. permixta to four commonly used insecticides. The results showed that winter forms (February) were 2.71‐fold, 4.58‐fold, 3.26 fold and 3.38‐fold more tolerant to diazinon, imidacloprid, acetamiprid and abamectin, respectively, compared with summer forms. Also, Esterase, GST and P450 monooxygenase activity was highest during February. Moreover, the content of lipid, carbohydrate, glycogen and protein was significantly higher in February compared with other months. Based on these results, the best period for insecticide treatment for efficient control is treatment against the first generation, at the time when eggs are laid by females as well as during the egg hatching and the larvae appearance. At this time of year, psylla are more susceptible, which would likely lead to better results and the reduction in damage during the next summer. However, further studies are needed to test this in farm settings, and to whether this holds true for other psylla species. [ABSTRACT FROM AUTHOR]

Problems resulting from excessive use of synthetic pesticides, including pest resistance and negative impacts on non-target organisms, have led to restrictions on the use of these compounds. The flour beetles, Tribolium castaneum and T. confusum are two of the most important pests of stored products worldwide. In the present study, the fumigant toxicity of an essential oil of Artemisia dracunculus to these pests was evaluated after 24 h of exposure. Activities of the major detoxifying enzymes were assessed at three different concentrations of essential oil (LC30, LC50 and LC70). The essential oil was significantly more toxic to T. castaneum (LC50= 67.2 µl/L air) than to T. confusum (LC50 = 178.4 µl/L air). The activity of GST (glutathione S-transferase) and MFOs (mixed function oxidases) of T. castaneum was positively and negatively correlated with increasing the essential oil doses, respectively. However this statistical relationship was reverse in T. confusum. Induction of GST in T. confusum might account for the lesser susceptibility of this species to the essential oil of A. dracunculus, while T. castaneum just showed a slight enhancement in the enzyme activity. [ABSTRACT FROM AUTHOR]

Dissipation kinetics of diazinon was investigated in soils culled from a paddy field with a long history of the pesticide application. Goodness of fit statistical indices derived from several fitted mono- and bi-exponential kinetic models revealed a bi-phasic pattern of the diazinon dissipation curve at 15 and 150 mg kg spiking levels, which could be described best by the first-order double exponential decay (FODED) model. Parameters obtained from this model were able to describe the enhanced dissipation of diazinon as the result of repeated soil applications, where a larger fraction of the pesticide readily available in the solution phase was dissipated with a fast rate. Cluster and principal component analysis (PCA) of denaturing gradient gel electrophoresis (DGGE) obtained from soil bacterial populations revealed that they were only affected at the 150 mg kg diazinon concentration. This was also supported by the phylogenetic tree obtained from sequences of the main gel bands. Accordingly, bacterial populations belonging to Proteobacteria were enriched in the soil following three treatments with diazinon at 150 mg kg. The Shannon's index revealed a nonsignificant increase ( P ≤ 0.05) in overall diversity of soil bacteria following diazinon application. Diazinon-degrading bacteria were isolated from the paddy soils in a mineral salt medium. Results showed that the isolated mixed culture was able to remove 90% of the pesticide at two concentrations of 50 and 100 mg L by 16.81 and 19.60 days, respectively. Sequencing the DGGE bands confirmed the role of Betaproteobacteria as the main components of the isolated mixed culture in the degradation of diazinon. [ABSTRACT FROM AUTHOR]

Background: Artemia urmiana are small crustaceans that because of its non-selective filter feeder pattern potentially may absorb high level of heavy metals through their living environment. In this study, the effects of different levels of cadmium and copper on survival, catalase activity and metals bioconcentration rates in A. urmiana nauplii have been investigated. Methods: The research was carried out in February 2012 at University of Tehran, Tehran, Iran. First experiment was conducted in nine concentrations with six replication, then LC50 and probable interactions between experimental metals were evaluated. In the second experiment, concentrations of metals absorbed by Artemia and catalase activity were measured based on the acute toxicity indices, including NOEC, LOEC and LC50 at individual and mixed concentrations. Results: The toxicity of copper sulphate (LC50= 29.87) was 2.5 times greater than cadmium chloride (LC50=79.08) and the toxicity interaction between cadmium and copper was synergistic. The rate of copper uptake in Artemia was higher than cadmium and increased concentration of heavy metals significantly decreased the bioconcentration factor. Comparison of mixed and individual concentrations showed that cadmium significantly decreased copper uptake, while it seems that cadmium bioconcentration was improved consequently. Biochemical analysis showed that the catalase activity was affected undesirably in different individual and mixed concentrations; however, these changes were not significant. Conclusion: A. urmiana nauplia seems to be highly resistant toward cadmium and copper in their culture medium and demonstrated excessive potential for uptake of heavy metals from their rearing environment. [ABSTRACT FROM AUTHOR]

The daily susceptibility rhythm of the cotton aphid, Aphis gossypii Glover, to diazinon and the corresponding changes in the activity of three xenobiotic detoxifying enzymes--cytochrome P450 monooxygenases (P450), glutathione S-transferases (GSTs), and esterases--were investigated. Bioassays were conducted to estimate the median lethal doses (LD50) of diazinon at six different zeitgeber times (ZT0, 4, 8, 12, 16, and 20) under constant light (LL) and lighting conditions of 16 h of light and 8 h of darkness (LD). The results showed that the highest susceptibility occurred at the onset of night (ZT16) and 4 h before this time point (ZT12) under the LD condition. The endogenous rhythmicity of susceptibility was ensured, as the highest susceptibility occurred at the same time under the LL condition. The circadian changes in susceptibility to diazinon were almost coincident with changes in esterase and GSTs activity, but not in P450 activity. We also found rhythmic changes in energy components of whole-body aphids, with similar patterns of circadian changes of proteins, lipids, and soluble carbohydrates, but not glycogen, under LL and LD conditions. These photoperiod conditions (LD and LL) showed different fluctuation in trends of energy resources and of course, different quantities. Our study represents the first report of circadian control of insecticide susceptibility in aphids and provides insights into more efficient control of these pests by unveiling the times of day during which aphids are more susceptible to insecticides with attention to endogenous physiological phenomena. [ABSTRACT FROM AUTHOR]