toxicity

The lesser grain borer, Rhyzopertha dominica (F.), with a worldwide distribution, is among the important pests of stored products, which causes significant economic damage to cereal grains such as wheat and rice. The lethal and sub-lethal effects of essential oils extracted from two species of the Mentha, including Mentha piperita L. and Mentha spicata L., on biological and life-table parameters and nutritional indices of R. dominica at 28±1°C, 60±5% relative humidity, and 14:10 h (light:darkness) photoperiod were evaluated in the current study. Results indicated that both essential oils were toxic to the adults of R. dominica, in which M. piperita essential oil with lower LC50 (16.72 and 12.55 μl/l, respectively) had more fumigant toxicity compared toM. spicata essential oil (41.11 and 35.73 μl/l, respectively) after 24 and 48 h. The egg incubation period and development time of immature stages were increased by essential oils' treatments. Female fecundity and adults longevity along with population parameters of the pest, including r (intrinsic rate of population increase), R0 (net reproductive rate), GRR (gross reproductive rate), and λ (finite rate of population increase), exposed to the essential oils were decreased. Nutritional indices, including consumption index, relative consumption rate, and relative growth rate, of pest treated with essential oils were also significantly reduced compared to the control group. Results revealed that M. piperita and M. spicata essential oils, as available and eco-friendly botanical agents, possess significant potential for the management of R. dominica.

Due to several side-effects of chemical pesticides' utilization and necessity of the introduction of efficient and eco-friendly alternatives, the insecticidal effects of ajwain, cumin, and fennel essential oils, separately and in combination, were investigated against the saw-toothed grain beetle in the present study. Chemical analyses of the essential oils revealed that thymol (43.07%) and cymol (26.16%) in ajwain, g-terpinene (39.89%) and cymol (31.96%) in cumin, and anethole (70.98%) and limonene (18.95%) in fennel essential oils were dominant. The 50% lethal concentration ​​(LC50) values of cumin, ajwain, and fennel essential oils were decreased from 0.701, 1.492, and 1.805 μl/g in 24 h to 0.394, 0.603, and 0.613 μl/g after 72 h, respectively. The combined use of the studied essential oils increased their toxicity and the mortality of pest; so the mixing of 30% lethal concentrations (LC30) of ajwain and cumin essential oils had a synergistic effect on the mortality of insect pest. In other combinations, an additive effect was observed in the toxicity of essential oils. Nutritional indices of the pest including consumption index, relative consumption rate, and relative growth rate, influenced by separate and combined application of ​​ essential oils, were significantly decreased compared to the control group. The relative growth rate of the pest showed the greatest reduction by ajwain+cumin+fennel essential oils' treatment compared to others. The results of the present research showed that it is possible to use ajwain, cumin, and fennel essential oils, separately and in combination, to manage saw-toothed grain beetle.

The flour beetle (Tribolium confusum du Val) is one of the most important coleopteran pests on stored products, especially cereal grains and flour. Frequent application of chemical pesticides in insect pest management has resulted in numerous side effects such as environmental contamination, threat to human health and non-target organisms, and the development of pest resistance. In the present study, the fumigant toxicity and anti-nutritional effects of rosemary essential oil on flour beetle adults were investigated. Due to the relationship between the chemical compositions of essential oils with their biological effects, the compounds of rosemary essential oil were studied by gas chromatography-mass spectrometry. Rosemary essential oil was rich in terpenic compounds, including the hydrocarbon monoterpenes (28.72%), monoterpenoids (57.03%), hydrocarbon sesquiterpenes (3.09%), and sesquiterpenoids (3.25%). The concentration of 73.5 µl/l air of essential oil caused 90.0% mortality of the pest after 24 h, which was increased to 100% by 48 h. The use of 24-h LC40 and LC50 values of essential oil, respectively equal to 26.7 and 35.5 µl/l air, reduces the nutritional indices of the pest, including consumption index, relative consumption rate, and relative growth rate after 5 and 10 days. In addition, the feeding deterrence index of the mentioned values was estimated at 40.7 and 45.9% after 5 days and 53.4 and 59.5% after 10 days, respectively. Therefore, rosemary essential oil can be introduced as one of the available and efficient agents in the management of flour beetle for further research.

Tea mealybug, Pseudococcus viburni (Signoret) is one of the important pests of tea and citrus orchards in Northern provinces of Iran. In the current study, the effect of several plant-based insecticides and microemulsion formulaion of Sophora pachycarpa leaf and root extract were investigated against tea mealybug under laboratory conditions by leaf dip method. The LC50 values of matrine, pepper extract, cinnamon and garlic essential oil, neem oil, coconut oil soap, castor oil, formulated leaf and root extracts of S. pachycarpa, and espiromesifen were determined as 2157, 1538, 2825, 5608, 4746, 6585, 4493, 5357 and 2676 mg formulated/l on adult of the tea mealybug, respectively. In addition, the LC50 of aforementioned compounds was calculated as 2188, 1555, 2809, 5559, 4703, 5842, 3457, 5195 and 1856mg formulated/l for third instar nymph of this insect, respectively. The bioassays showed that pepper extract, matrine, and cinnamon and garlic essential oil were most efficient treatments against tea mealybug. Treatments of third instar nymphs by the insecticides also affected the activity of detoxifying enzymes including alpha- and beta-esterases, acetylcholinesterase, glutathione S-transferase (GST) and MFO system. Pepper extract, cinnamon and garlic essential oil, and formulated leaf extract of S. pachycarpa decreased the activities of α-esterase. Since the pepper extract, matrine, cinnamon and garlic essential oil showed significant mortality against nymphs and adults of the tea mealybug these insecticides can be considered in the integrated management of the tea mealybug.

The tomato leaf miner, Tuta absoluta (Meyrick), is one of the important pests of tomato in Iran. In the present study, the lethal and sublethal effects of the insecticide alpha-cypermethrin + teflubenzuron by leaf dipping method were investigated against the second-instar larvae of the tomato leafminer on Early Urbana Y and Super strain B tomato cultivars. The results showed that the toxicity of alpha-cypermethrin + teflubenzuron to tomato leafminer larvae in the Early Urbana Y variety (LC50 = 4509 ppm) is more than its toxicity in the Super strain B (LC50 = 5595 ppm). Treatment with alpha-cypermethrin + teflubenzuron increased the larval and pupal periods and developmental time of the tomato leafminer in the Early Urbana Y compared to the Super Strain B and control group. The lowest longevity and fecundity of the tomato leafminer were observed in the Early Urbana Y. The life-table parameters of the pest, including intrinsic rate of increase (r) and finite rate of increase (λ), on the Early Urbana Y treated by alpha-cypermethrin + teflubenzuron (0.0479 and 1.0491 day-1, respectively) were significantly lower than corresponding amounts on the treated Super Strain B (0.0684 and 1.0708 day-1, respectively). Treatment with alpha-cypermethrin + teflubenzuron increased the mean duration of a generation (T) of pest compared to the control. The results of the present study indicated that the use of alpha-cypermethrin + teflubenzuron on the Early Urbana Y variety in the management of T. absoluta could be more effective than the Super strain B variety.

In this study, we performed quantum mechanics computation at density function theory level with 6-31G* basis set to construct a quantitative structure-toxicity relationship (QSTR) model for predicting lethal dose (LD50) pesticide carbamates derivatives. The best molecular descriptors were selected using genetic algorithm (GA) by MATLAB software. Then, we studied the relationship between the selected descriptors and the logLD50 of carbamate derivatives using backward-stepwise multiple linear regression (BW-MLR) and backpropagation artificial neural network (BP-ANN) models. The RDF010e, WW, and R3e descriptors were applied for modeling the GA-BWMLR and GA-BPANN models. The comparison of results illustrated that the R2 and Q2 of GA-BPANN model for all set were significantly higher than the GA-BWMLR model. The GA-BPANN model was more accurate with lower mean square error (MSE), root-mean-square error (RMSE), standard error of prediction (SEP), and absolute average deviation (ADD) values of data set for predicting the LD50 of studied carbamates.

Alder leaf beetle, Agelastica alni (Linnaeus, 1758) (Col.: Chrysomelidae) is an important pest of the alder trees in Iran. Both the beetle and its larvae feed on leaves of alder trees causing aesthetical and physiological damage. The toxicity of four commercial insect growth regulators (IGR) including lufenuron, flufenoxuron, hexaflumuron and pyriproxyfen was investigated on the second instar larvae (24 h old) of alder beetle, A. alni using the leaf dip method (for 30 s) under laboratory conditions [25 ± 1 ºC, 75 ± 5% RH and a photoperiod of 14:10 (L: D)]. The experiment was conducted in the toxicology laboratory of Guilan University. SPSS software was used for calculating LC50 values. 72 hours after treatment the insecticides proved to have high toxicity. In addition, these pesticides had negative effects on the morphology of larvae in the molting stage. LC50 values were estimated as 36.37 ppm for lufenuron, 48.35 ppm for flufenoxuron, 68.90 ppm for hexaflumuron and 54.37 ppm for pyriproxyfen, respectively. Abnormal morphological changes such as incomplete formation of the cuticle due to consumption of the pesticides by these larvae were observed. Considering that IGRs are safer to human and environment health, compared to conventional insecticides, these four IGRs especially lufenuron seems to be suitable candidates for development of IPM programs against alder leaf beetle.

Aphids are among the most important economic pests and vectors of many plant pathogens in horticultural, agricultural and greenhouse crops in world. In this study, the effect of ethanolic extract of nettle Urtica dioica L. (Rosales: Urticaceae), Palizin® soap and Firooz® baby shampoo on three species of aphids (black alfalfa aphid, Aphis fabae (Scopoli), wheat poison aphid, Schizaphis graminum (Rondani), and cowpea aphid, Aphis craccivora (Koch)) were examined. Several experiments included evaluation of the birth percentage of adult insects, total mortality and mortality of 5-6- and 1-2-day-old nymphs and also adult insects treated with the above compounds. Hosts of these pests in all steps of this study were included wheat plants for poisonous wheat aphids, alfalfa for black alfalfa aphids and beans for black bean aphids. The results of this study showed that ethanolic extract of nettle has a significant effect on pest mortality. The result showed the ethanolic extract of nettle has a significant effect with the means ± SE percentage of mortality (90.50±3.76) and (87.78±3.92) in wheat poison aphid, (74.00±9.30) and (79.00±5.76) in black alfalfa aphid and (62.00±9.20) and (64.50±4.56) in cowpea aphid on 1-2-and 5-6- day-old nymphs, respectively, in comparing to control. So, according to the results, ethanolic extract of nettle has a significant effect on the control of these pests and it can have capacities that suggest conducting further studies in the management of Aphids.

Cabbage white, Pieris brassicae (L.) (Lepidoptera: Pieridae) is an important pest of cruciferous in Iran and the world. In this study, the effect of four insecticides; hexaflumuron, spinosad, abamectin and indoxacarb on cabbage white and its parasitoid Cotesia glomerata L. was investigated The LC50 values obtained from the analysis of probit as a result of the effect of different concentrations of hexaflumuron, spinosad, abamectin and indoxacarb on the 3rd instar larvae of P. brassicae after 72 hours were (0.213, 0.298, 0.30 and 0.434) ml/L, respectively. The LC50 values obtained from the same insecticides on eggs of P. brassicae after 7 days were (0.831, 0.440, 0.267 and 0.489) ml/l, respectively. The results of the same compounds effects on parasitoid after 7 days showed that hexaflumuron and indoxacarb are the most harmful and abamectin is the least harmful for this natural enemy. The results showed that the most effective insecticides on 3rd instar larvae of P. brassicae during 72 hours was hexaflumuron. In the study of parasitization of third instar larvae of cabbage white under the influence of different concentrations of hexaflumuron, spinosad, abamectin and indoxacarb in compared with control, results showed at low concentrations of all four insecticides, there is no significant difference between control and insecticides, but there was a significant difference in higher concentrations and the mean number of third instar larvae in the control treatment increased. According to the results of this study, hexaflumuron can be suggested as a low-risk compound for parasitoid and effective against this pest.

The Greenbug, Schizaphis graminum Rondani (Hemiptera: Aphididae), is one of the most important pests in grain, especially wheat, and is an important cause for transferring a number of pathogenic viruses in plants. The purpose of this research was to evaluate the lethal and sublethal effects of Pymetrozine insecticide on life history parameters and α-esterase and β-esterase enzymes activity of S. graminum. Detoxifying enzymes play a vital role in the detoxification of chemical compounds in many living organisms. These enzymes increase the resistance of insects to chemical pesticides by the catalysis of these compounds in their body.

The S. graminum was reared on the wheat host in a growth chamber set at 25 ± 2 °C, 60 ± 5 % RH, plus 16: 8 (L: D) hour photoperiods. Daily observations and records were made for the development period and survival rate. The crude data were analyzed based on age-stage and two-sex life table analysis. TWO SEX-MSChart was used to evaluate the raw data based on the age-stage and two-sex life table. In addition, alpha-naphthyl (α-NA) and beta-naphthyl (β-NA) acetates were employed as substrates for the α-esterase and β-esterase activity, respectively. Esterase enzymes of tested treatments were measured using a microplate reader.

Exposing adults to bioassays indicated that the lethal concentration (LC50) of insecticide treatment in S. graminum adults was 84.68 mg a.i./L. The present study demonstrated that Pymetrozine insecticide showed more acute toxicity on adult stages of S. graminum. Moreover, exposure of adults to sublethal concentrations (LC30) negatively affected the development and reproductive characteristics and demographic factors of the Greenbug. In specific, results for sublethal experiments showed a significant increase in the development time of the pest on the insecticide treatment compared with the control. On the contrary, the lowest fecundity in pests was observed on Pymetrozine insecticide. In addition, the tested insecticide significantly reduced the population growth parameters of S. graminum, which can be identified using detoxifying enzymes as biochemical markers of the pest. Estimation values for the intrinsic rate of increase (r) in the control and insecticide treatment were 0.394 and 0.280 per day, respectively. Furthermore, the activity of alpha and beta esterase was not significantly different between control and insecticide treatment.

The results revealed that Pymetrozine insecticide exerts high lethal and sublethal effects on S. graminum, and thus, it is recommended to be applied in an integrated pest management program (IPM). Semifield and field studies are needed to obtain more applicable results using insecticides.

Due to the effects of overuse of chemical pesticides and the residual problems in greenhouse products that threaten the health of consumers and exports, the use of low-risk alternatives such as plant compounds and biological agents has become necessary. Therefore, in this research, the effect of three commercial formulations of neem plant  (Azadirachta indica A. Juss.) composition, including Nimbecidine, NeemAzal T/S and Kofa was evaluated on the biological stages of Trialeurodes vaporariorum (Hem.: Aleyrodidae), and its parasitoid, Encarsia formosa Gahan. In evaluating the lethal effect of three commercial formulations, the highest lethal effect on eggs after 7 days related to Nimbecidine formula with LC50 equal to 774.71 ppm. The highest lethal effect on 3rd nymphal stage and adult whitefly after 72 hours with LC50 equal to 402.89 and 655.51 ppm in Nimbecidine formula were observed, respectively. A similar effect was obtained on parasitoid. In evaluating the oviposition preference of E. formosa for by choice and non-choice methods, the tendency of E. formosa to control was more than the formulas. The highest probability of oviposition of parasitoid in Kofa formula was observed (%42.66). The results of this study showed that all three formulas can be used in integrated management of this pest and when the emergence and use of E. formosa parasitoid, Kofa formula and in the absence of parasitoid, Nimbecidine formula is recommended.

 Citrus red mite, Panonychus citri is an important plant pest species in the citrus growing regions of the world. Due to the use of chemical pesticides with a wide range of effects against this pest and other pests in citrus orchards, P. citri has been become a serious pest in citrus orchards, including citrus orchards in the north of the country. In this study, the acaricidal and sublethal effects of diflovidazin on different stages of citrus red mite were investigated. The results showed that diflovidazin was highly toxic to the eggs, larvae and deutonymph stages of citrus red mite. The sublethal effects of diflovidazin on the parameters of citrus red mite life table were investigated and the results showed a significant decrease in generation length average, adult longevity, fecundity and fertility period. The net reproduction rates (R0) were 11.2 and 1.62 offspring per female mite for control and treatment of diflovidazin, respectively. The intrinsic (r) and finite (λ) rates of increase for the control were 0.133 and 1.142 per day, respectively, and for the LC30 treatment was 0.033 and 1.034 per day, respectively. In general, the sub-lethal concentration of difluvidazine showed a diminishing effect on all population growth parameters in treated deutonymphs. Overall, the results indicate the lethal and sub-lethal effects of diflovidazin on citrus red mites, and this compound can be recommended as part of a resistance management program to control this mite.

Background and Objectives Tetranychus urticae, as the two-spotted spider mite, is considered as one of the most important and destructive herbivorous mites in farms and greenhouses, which is very important to control due to its wide host range. The damage caused by agricultural pests combined with the harmful effects of synthetic chemicals used in their control can be mitigated or eliminated by using botanicals, which are derived from renewable resources including a mixture of various bioactive ingredients. Therefore, finding a suitable alternative way for controlling this pest is necessary by considering the resistance to acaricides, as well as undesirable effects of chemical compounds. The present work aims to evaluate microcapsule essential oil of Mentha piperita and its lethal and sublethal toxicity to T. urticae. Materials and Methods Laboratory bioassays were used for evaluating the sublethal effects of peppermint essential oil microcapsules on biological and population parameters of T. urticae. The life table parameters of T. urticae were conducted on leaf discs under laboratory conditions at 25 ± 2°C, 60 ± 5% relative humidity, and a photoperiod of 16:8 (L: D) hours. Then, the duration of each stage, developmental time, and survival were observed and recorded daily. In addition, the raw data were analyzed based on age stage two-sex life table theory with MS-Chart. Results Based on the results, microcapsules of Menthe piperita caused a significant reduction in fecundity and longevity. Those treated with LC20 and LC30 had a significant reduction at net reproductive rate, compared to those treated with LC10 and untreated ones. The intrinsic and finite rate of increase reduced significantly in higher concentration compared to the control. In addition, the mean generation time decreased significantly at the upper dose, compared with LC10. Discussion Botanic acaricides can be used for controlling Tetranychus urticae, and the microencapsulated formulation of these products makes them more stable. Familiarity with the chemical nature of the bio-active pesticide/acaricidal compound can be considered in future research which can play a role in developing an effective and environmentally friendly treatment against spider mites, leading to a decrease in reliance on synthetic pesticides/acaricides. The results of this study can be used in designing the mentioned pest management programs by considering the detrimental effects of M. piperita essential oil microcapsule on some biological parameters of T. urticae.