LC50 Concentration Research Articles

Toxicity and physiological interruptions of a proteinaceous toxin from Metarhizium anisopliae against the olive fruit pest, Bacterocera oleae (Diptera: Tephritidae)

The use of natural bioactive compounds mainly proteinaceous secondary metabolites of fungi is one of the promising pest control methods because of their lethal effects on insects in low concentration, limited persistence in environment and easily decomposition into environmentally safe compounds. The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a destructive pest of olive fruits around the world. In the current study, the proteinaceous compounds were extracted from the two isolates (MASA and MAAI) of Metarhizium anisopliae and their effects were evaluated on toxicity, feeding performance and antioxidant system of the adult's olive flies. Both extracts from MASA and MAAI showed entomotoxicity against the adults by 2.47 and 2.38 mg/mL as LC50 concentrations. Also, LT50 values were recorded 1.15 and 1.31 days for MASA and MAAI, respectively. No statistical differences were recorded in the consumption rate of the adults on control and secondary metabolite contained protein hydrolysate. In contrast, the adults fed on LC30 and LC50 concentrations of MASA and MAAI demonstrated significant reduction in the activities of digestive alpha-amylase, glucosidases, lipase, trypsin, chymotrypsin, elastase, amino- and carboxypeptidases. Activity of antioxidant enzymes changed in the adults of B. oleae fed on the fungal secondary metabolites. Catalase, Peroxidase and Superoxide dismutase elevated in the treated adults with the highest amounts of MAAI. Similar results were found in activity of ascorbate peroxidase and glucose-6-phosphate dehydrogenase except for malondialdehyde amount in which no statistical differences were recorded between treatments and control. Relative gene expression of caspase enzymes revealed the higher expression in the treated B. oleae compared to control with the highest level of caspase 8 for MASA and caspases 1 and 8 for MAAI. Results of our study showed that the secondary metabolites extracted from the two isolates of M. anisopliae caused mortality, interrupted digestion and induced oxidative stress in the adults of B. oleae.

Green synthesis, characterization, acaricidal, larvacidal, and repellent activities of copper nanoparticles of Astragalus sinicus against Hyalomma anatolicum

Objective: To green synthesize and characterize copper nanoparticles (CuNPs) using Astragalus sinicus, as well as evaluate the acaricidal, larvacidal, and repellent activities of CuNPs against Hyalomma anatolicum (H. anatolicum), one of the most prevalent ticks infesting cattle in Saudi Arabia. Methods: CuNPs were green synthesized by adding the Astragalus sinicus extract to a copper sulfate solution. The acaricidal, larvicidal, and repellent activities of CuNPs against H. anatolicum were assessed via the adult immersion test, the larval packet test, and the vertical movement behavior of tick larvae, respectively. The effects of CuNPs on acetylcholinesterase as well as oxidative enzyme activities were examined. Results: The green synthesized CuNPs displayed a spherical form with a size range of 15-75 nm. After exposure of adult H. anatolicum to different concentrations of CuNPs, the viability rate of adult H. anatolicum and the mean number, weight, and hatchability of eggs were noticeably reduced, in comparison to the control group (P<0.001). In addition, the viability rate of larvae considerably declined (P<0.001) with the LC50 and LC90 values of 11.30 and 20.34 μg/mL, respectively. The maximum repellent activity of CuNPs was observed at 50, 100, and 200 μg/mL with complete repellent activity after 60, 120, and 180 min of exposure, respectively. CuNPs, mainly at ½LC50 and LC50 concentrations, markedly suppressed the acetylcholinesterase activity of the larval stage of H. anatolicum (P<0.001). Moreover, CuNPs, mainly at LC50 dose, significantly elevated malondialdehyde level while declining glutathione-S-transferase level in H. anatolicum larvae (P<0.001). Conclusions: CuNPs show potent acaricidal, larvicidal, and repellent activities against adults and larvae of H. anatolicum. However, further studies must be performed to clarify the precise mechanisms and the efficacy of CuNPs in practical use.

Chemical composition and toxicity of Artemisia herba-alba essential oil against Cydia pomonella L. (Lepidoptera:Tortricidae) under laboratory conditions

The codling moth Cydia pomonella L. (Lepidoptera: Tortricidae) is a destructive pest of apples and pears worldwide. Due to the phytotoxic effect of chemical fumigant on postharvest apple, botanical insecticides are an interesting alternative to synthetic chemical insecticides regarding their low environmental impact. Hence, in the present study, we investigated the chemical composition and fumigant toxicity of Artemisia herba-alba essential oil against the fifth-instar codling moth, under laboratory conditions. In total, 49 compounds were identified by gas chromatography/mass spectrometry. The major constituents determined were dextro-camphor (30.60%), 2,6-dimethyl-1,3,6-heptatriene (26.71%), safranal (7.04%), borneol (3.94%) and eucalyptol (3.47%). A. herba-alba essential oil showed strong larvicidal activity, with minimum lethal concentration LC50 values of 13.49 and 04.45 μl L-1 air at 24 h and 48 h, respectively. The LT50 values at the lowest (1.81 μl L-1 air) and highest oil concentrations (18.18 μl L-1 air) were, in turn, 59.35 to 19.52 h. The obtained results indicated that essential oil of A. herba-alba may have a potential to be developed as a botanical fumigant against the fifth-instar codling moth.

Toxicological effect of endocrine disrupting heavy metal (Pb) on Mekong silurid Pangasius catfish, Pangasius hypophthalmus

The current study aimed to investigate the effects of lead nitrate exposure on the enzymatical, haematological, and histological changes in the gill, liver, and kidney of Pangasius hypophthalmus. The fish were divided into six groups and treated with different Pb concentrations. The LC50 value of Pb was 55.57 mg/L at 96 h for P. hypophthalmus, and sublethal toxicity was assessed for 45 days at 1/5th (11.47 mg/L) and 1/10th (5.57 mg/L) of LC50 concentration. Enzymes such as aspartate aminotransferase (AST), alanine aminotransferase (ALT) levels, alkaline phosphate (ALP), and lactate dehydrogenase (LDH) content increased significantly during sublethal toxicity of Pb. The reduction of HCT and PCV indicates an anemic condition due to the toxicity of Pb. Differential leucocytes, lymphocytes, and monocytes and their % values significantly decreased, indicating Pb exposure. The main histological changes observed in the gills were the destruction of secondary lamellae, the fusion of adjacent gill lamellae, primary lamellae hypertrophy, and severe hyperplasia, while in kidney exposed to Pb showed melanomacrophages, increased periglomerular, peritubular space, vacuolation, shrunken glomerulus, destruction of tubular epithelium, and hypertrophy of distal convoluted segment. The liver showed severe necrosis and rupture of hepatic cells, hyper trepheoid bile duct, shifting of nuclei, and vascular hemorrhage, while in the brain, binucleus, mesoglea cells, vacuole, and ruptured nucleus were observed. In conclusion, P. hypophthalmus, which has been exposed to Pb has developed a number of toxicity markers. Consequently, prolonged exposure to higher Pb concentrations may be harmful to fish health. The findings strongly suggest that the lead had a detrimental impact on the P. hypophthalmus population, as well as on the water quality and non-target aquatic organisms.

Mosquito adulticidal activities of crude extracts from above ground part of Laggera pterodonta (D.C) Sch.Bip and Laggera aurita (D.C) Sch.Bip against malaria vector, Anopheles gambiae

Mosquitoes are small, midget flies that transmit harmful infections such as malaria, yellow fever, and dengue fever in Nigeria. Its control using a synthetic insecticide is becoming increasingly difficult due to high cost, persistence in the environment, and development of resistance by the mosquitoes. The aim of this study is to evaluate the adulticidal activity of crude ethanolic extract of the above ground parts of Laggera pterodonta and Laggera aurita against adult Anopheles gambiae. Dried Laggera pterodonta and Laggera aurita were individually macerated with 70% ethanol to obtain the crude extract. Phytochemical screening revealed the presence of saponin, flavonoids and terpenoids in both Laggera pterodonta and Laggera aurita while tanins and alkaloids were present in Laggera aurita only. The extracts were tested against 4-5 days old laboratory-reared adult Anopheles gambiae. The findings revealed that the adulticidal lethal concentration LC50 of L. pterodonta crude extract was 4553 mg/L while the LC50 of L. aurita was 5582 mg/L. The result suggests the extracts are potential natural insecticides against adult An. gambiae mosquitoes.

Antioxidant, antibacterial and insecticidal activities of cypress (Cupressus sempervirens L.) essential oil

ABSTRACT The aerial parts of cypress (Cupressus sempervirens L.) of three collect regions (Bizerte, Ben-Arous and Nabeul) were reported for their essential oil (EO) compositions, antioxidant, antimicrobial and insecticidal activities. Results showed that the higher EO yields were observed in Bizerte and Ben Arous (0.56%), followed by Nabeul (0.49%). The EO composition showed the predominance of α-pinene with 36.72% in Bizerte, 30.22% in Nabeul and 30% in Ben-Arous. Cypress EO of Bizerte showed higher antiradical capacity (IC50 = 55 µg/mL) than Ben-Arous (IC50 = 97.50 µg/mL) and Nabeul (IC50 = 155 µg/mL). E. faecalis was the most sensitive strain to cypress EO of Bizerte with the largest inhibition zone (IZ = 65 mm). Regarding the insecticidal activity, cypress EO of Bizerte had the highest mortality of Tribolium castaneum with a lethal concentration of LC50 = 164.3 µL/L air after 24 h exposure.

Phytochemical profiling, antioxidant activities, enzymatic activities and insecticidal potential of aqueous extracts of four plants on the larvae of Helicoverpa armigera (Lepidoptera: Noctuidae), the main pest of cotton plant in Ivory Coast.

In the context of climate change, the Ivorian cotton industry is facing with the loss of sensitivity of pests (Helicoverpa armigera) and the appearance of new so-called emerging insects. Faced with this situation, cotton producers tend to use insecticide products in high doses, in excess of the norm. However, the misuse of chemical products poses many health risks. Therefore, to limit the use of chemicals, aqueous extracts of local plants with insecticidal properties were examined in the laboratory and in the field. Four local plant species were selected [Anacardium occidentale (Anarcardier); Azadirachta indica (Neem); Hyptis suaveolens (Hyptis) and Tephrosia vogelii (Tephrosia)]. After determining the chemical profiles of the four extracts by high performance liquid chromatography (HPLC)-mass spectrometry, their inhibitory activities were assessed in cholinesterase and tyrosinase. The sensitivity of Helicoverpa armigera larvae was evaluated by ingesting the aqueous extracts at several concentrations ranging from 2% to 64% in an artificial nutrient substrate. Then, the mortality rates of the larvae during 72 h were evaluated and the lethal concentrations were determined. The results of chemical analyses (HPLC) showed that the richest aqueous extract in phytochemicals with 54 elements detected was that of cashew (A. occidentale). T. vogelii, A. indica and H. suaveolens presented 44, 45, and 39 chemical compounds, respectively. In addition, the total phenolic content was higher in A. occidentale (110.67 mg gallic acid equivalents/g) followed by A. indica (42.43 mg gallic acid equivalents/g). The highest antioxidant ability was observed with the aqueous extract of cashew (A. occidentale). Anti-enzymatic activities such as acetylcholinesterase, butyrylcholinesterase and tyrosinase inhibition were most pronounced in A. occidentale (2.35 ± 0.02 mg galanthamine equivalent/g, 3.77 ± 0.01 mg galanthamine equivalent/g and 71.28 ± 0.07 mg kojic acid equivalent/g, respectively). The most toxic aqueous extract for H. armigera larvae was that of cashew with a lethal concentration LC50 = 11.68%. Moreover, the principal component analysis performed showed that the insecticidal activity is strongly correlated with the antioxidant and enzymatic activities of the aqueous extracts. Then, the hierarchical ascending classification showed cashew as the best plant. For the sustainability of cotton production, it would be necessary to limit the use of chemical-synthetic insecticides through the use of plant extracts, especially from cashew leaves.

Reduced Survival and Disruption of Female Reproductive Output in Two Copepod Species (Acartia clausi and A. tonsa) Exposed to the Model Endocrine Disruptor 17α-Ethinylestradiol.

Estuaries are heavily impacted by pollutants from different sources such as urban sewage, industrial waste and agricultural runoff. Endocrine-disrupting chemicals (EDCs) are very concerning pollutants to estuarine wildlife, but little is known about their impact on microscopic biota such as zooplankton. The aim of this work was to investigate the effects of a model EDC, the 17α-ethinylestradiol (EE2), on two copepod species inhabiting the Basque coast (Southeastern Bay of Biscay) estuaries: Acartia clausi (autochthonous neritic species) and Acartia tonsa (non-indigenous brackish species). Female copepods were collected at population maximum time (spring for A. clausi and summer for A. tonsa) and exposed individually to 5 ng/L (low), 5 µg/L (medium) and 500 µg/L EE2 (high) doses, from environmental concentrations found in sewage effluents to toxicological concentrations. After 24 h exposure, the survival rate of experimental individuals was checked and the lethal concentration LC50 was calculated. The number of egg-producing females and the amount of egg laying and egg hatching were recorded. The integrated biomarker index (IBR) was calculated to integrate the overall effects of EE2 exposure. Both species had reduced survival rates at 500 µg/L, and the LC50 was lower in A. tonsa (158 µg/L) compared to A. clausi (398 µg/L). The number of eggs laid was significantly reduced in A. clausi at EE2 medium and high doses, while a reduction in the number of eggs in A. tonsa was observed only at the high dose. However, no significant differences were detected in the egg hatching success of exposed A. clausi and A. tonsa. IBR index showed that EE2 had the most detrimental effects on A. tonsa and A. clausi females at the 500 µg/L dose. In conclusion, after 24 h of exposure, EE2 reduced female copepod survival and disrupted reproductive output, but only at high non-environmentally relevant concentrations.

Evaluating the Sublethal Effects of Origanum vulgare Essential Oil and Carvacrol on the Biological Characteristics of Culex pipiens biotype molestus (Diptera: Culicidae).

Culex pipiens is a mosquito species complex spread worldwide that poses a serious threat to human health as the primary vector of West Nile virus. Its control is mainly based on larvicidal applications with synthetic insecticides on mosquito breeding sites. However, the excessive use of synthetic larvicides may provoke mosquito resistance issues and negative side effects to the aquatic environment and human health. Plant-derived essential oils, including those from the Lamiaceae family, can be eco-friendly alternative larvicidal agents causing acute larval toxicity and/or growth inhibitory effects on the developmental stages of mosquitoes through different modes of action. In the current laboratory study, we evaluated the sublethal effects of carvacrol-rich oregano essential oil and pure carvacrol on Cx. pipiens biotype molestus, the autogenous member of the Cx. pipiens species complex, after the exposure of 3rd-4th instar larvae to LC50 concentrations. The short-term (24 h) larvicidal treatment with the sublethal concentrations of both tested materials exhibited an acute lethal effect on the exposed larvae as well as significant delayed mortality for surviving larvae and pupae. Larvicidal treatment with carvacrol reduced the longevity of the emerged males. In addition, the morphological abnormalities that were observed at the larval and pupal stage along with failed adult emergence indicate the potential growth inhibitory properties of the tested bioinsecticides. Our findings suggest that carvacrol and carvacrol-rich oregano oil are effective plant-based larvicides at doses lower than the acute lethal ones, thus promoting an environmentally friendly and more affordable perspective for their use against the WNV vector Cx. pipiens biotype molestus.

Biochemical, Histological Changes, Protein Electrophoretic Pattern, and Field Application of CuPb-Ferrite/TiO2 Nanocomposites for Controlling Terrestrial Gastropod Eobania vermiculata (Müller).

Eobania vermiculata is a hazardous snail that can damage ornamental plants and cause significant harm to plant sections in Egyptian areas. Herein, the molluscicidal activity of CuPb-Ferrite/TiO2 and TiO2 nanoparticles (NPs) against E. vermiculata was evaluated using the poisonous bait method. LC50 values were determined using the leaf dipping and contact methods, with values of 631.23 and 1703.49 ppm for CuPb-Ferrite/TiO2 and 193.67 and 574.97 ppm for TiO2. Exposure to both NPs resulted in a significant increase in the biochemical parameters of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP), as well as a decrease in total protein (TP) percentage of E. vermiculata. Histological examinations revealed that many digestive cells had ruptured, and their contents had been lost, while the foot's epithelial layer became ruptured. The average reduction was 66.36% for CuPb-Ferrite/TiO2 NPs compared to the recommended molluscicide, Neomyl, with a 70.23% reduction in the field application. Electrophoretic separation of total protein using sodium dodecyl sulfate-polyacrylamide gel electrophoresis after treatment with LC50 concentrations of TiO2 and CuPb-Ferrite/TiO2 demonstrated the potency of these synthetic compounds as molluscicidal agents. Therefore, we recommend the use of CuPb-Ferrite/TiO2 NPs as a novel land snail molluscicide because it is safe to use, and the baits are arranged to not affect irrigation water, with a high molluscicidal effect.

Interaction of spirodiclofen, fenpyroximate, etoxazole, and imidacloprid for the control of two-spotted spider mite, Tetranychus urticae Koch

ABSTRACT The interaction relationships of a binary mixture of spirodiclofen, fenpyroximate, and etoxazole acaricides, and mixing each of these acaricides with imidacloprid were investigated on deutonymph of Tetranychus urticae using the Potter spray tower method under controlled laboratory conditions. Based on the results of bioassay tests and combination index (CI) estimates, the toxicity of the binary mixture of the tested acaricides with each other and with imidacloprid on T. urticae was lower than that of each compound alone, and the interaction of their binary mixture was the antagonistic type. The measurement of the activity level of detoxifying enzymes in T. urticae treated with the LC50 concentration of pesticides and their binary mixture showed that the highest α- and β-esterase and glutathione S-transferase (GST) activities were observed in mites treated with spirodiclofen. Additionally, the highest cytochrome P450 monooxygenases (MFO) content was detected in mites treated with a mixture of spirodiclofen and imidacloprid. The results indicated that the application of a binary mixture of the mentioned acaricides together and in combination with imidacloprid leads to inefficient control of T. urticae.

Acute oral toxicity, apoptosis, and immune response in nurse bees (Apis mellifera) induced by flupyradifurone.

The potential toxicity of flupyradifurone (FPF) to honey bees has been a subject of controversy in recent years. Understanding the effect of pesticides on nurse bees is important because the fitness of nurse bees is critical for in-hive activities, such as larval survival and performing hive maintenance. In order to evaluate the acute oral toxicity of flupyradifurone on nurse bees, flupyradifurone at five different concentrations was selected to feed both larvae and nurse bees. Our results showed that nurse bees were more sensitive to flupyradifurone than larvae (LD50 of the acute oral toxicity of flupyradifurone was 17.72μg a.i./larva and 3.368μg a.i./nurse bee). In addition, the apoptotic rates of neurons in mushroom bodies of nurse bees were significantly induced by flupyradifurone at sublethal concentrations (8mg/L, 20mg/L, and 50mg/L) and the median lethal concentration LC50 (125mg/L). The expression of immune-related genes (Hsp90, Toll-8/Tollo, and defensin) was significantly changed in exposed nurse bees at the field-realistic concentration of flupyradifurone. However, three detoxifying enzyme genes (CYP9Q1, -2, and -3) were not affected by pesticide exposure. Our data suggest that although flupyradifurone had a relatively lower acute oral toxicity than many other common pesticides, exposures to the field-realistic and other sublethal concentrations of flupyradifurone still have cytotoxicity and immune-responsive effects on nurse bees. Therefore, flupyradifurone should be considered for its application in crops.

Enantioselectivity of indoxacarb enantiomers in Bombyx mori larvae: toxicity, bioaccumulation and biotransformation.

Indoxacarb is a chiral insecticide with excellent insecticidal activity against lepidopterous insects. Because of their enantioselectivity, chiral pesticides' environmental behavior at the enantiomeric level has been highlighted. The chiral stability, enantioselective bioaccumulation, biotransformation behavior of indoxacarb to a non-target insect silkworm are still unclear. A chiral analysis method for indoxacarb and its metabolite DCJW in silkworm was developed using liquid chromatography and high-resolution mass spectrometry (HPLC/HRMS). In silkworms, the recoveries of indoxacarb and DCJW were 86.06%-104.52% with relative standard deviation (RSD) < 9.01%. The 96-h lethal concentration (LC50 ) values of R-indoxacarb, S-indoxacarb, and enriched S-indoxacarb (2.333 S/1R) were 1.08 × 102 , 1.92, and 6.89 mg a.i. L-1 , respectively, according to the acute toxicity test results. When silkworm larvae were exposed to 1/50 of the LC50 concentration, the bioconcentration factor (BCF) of R-indoxacarb was 0.0296-0.318, and the BCF of S-indoxacarb was 0.0125-0.211. In silkworm larvae, the amount of R-DCJW produced by R-indoxacarb was 0.00610 to 2.34 times that of the parent R-indoxacarb, and the amount of S-DCJW produced by S-indoxacarb was 0.125-36.9 times that of the parent S-indoxacarb. There was no chiral transition from S-indoxacarb to R-indoxacarb or a transformation from R-indoxacarb to S-indoxacarb. Indoxacarb was preferentially bioaccumulated in silkworm larva, while S-indoxacarb bioconversion into the metabolite S-DCJW was much greater than R-indoxacarb bioconversion into R-DCJW. This study could improve understanding of the indoxacarb accumulation and transformation process in insects, as well as provide more scientific data for indoxacarb environmental and ecological risk assessment. © 2023 Society of Chemical Industry.

The impact of Cyflumetofen on demographic parameters of two predatory mites, Neoseiulus californicus (M-G) and Phytoseiulus persimilis (A-H)

The assessment of the long-term negative effects of acaricides on the target and non-target mites can help determine the toxicity and side effects of acaricides. The sublethal concentrations can be very precise and affect populations at concentrations lower than the conventional concentration and may supplement our knowledge about its sublethal effects on the physiology and behavior of insects/mites. Furthermore, we exposed the adults' biocontrol agents mite, Phytoseiulus persimilis Athias-Henriot and Neoseuilus californicus McGregor, to the LC10 and LC30 concentrations of the Cyflumetofen and then assayed the effects of these concentrations on the growth and development of the next generations under laboratory conditions. Analyzed data showed that sublethal concentrations of cyflumetofen significantly affected both species' biological parameters, including the total lifetime, fecundity, and longevity of the treated biocontrol agents compared with the control treatment. Due to our results, when P. persimilis and N. californicus adults were exposed to LC30 concentration of cyflumetofen, the length of the oviposition period of the treated P.persimilis and N. californicus were 20.34 and 19.66 days, respectively. At the same time, these values for the control-treated P. persimilis and N. californicus were 22.51 and 22.21, respectively. The intrinsic rate of increase (r) in control were 0.203 and 0.238, while those treated with LC10 and LC30 of cyflumetofen were estimated to be 0.238 and 0.214 for P. persimilis and 0.203 and 0.223 days−1, for N. californicus, respectively. Therefore, using sublethal concentrations of cyflumetofen is emphasized for designing integrated pest management programs and makes it possible to use biocontrol agents to control the spider mite; thus, it would benefit the farmers and consumers in the long run.

A Study on the Toxicity and Sublethal Concentrations of Three Insecticides on the Population Dynamics of Green Lacewing Chrysoperla carnea Stephens

Alsendi, A., A.A. Kareem, M. Havasi and Gh. Golmohammadi. 2023. A Study on the Toxicity and Sublethal Concentrations of Three Insecticides on the Population Dynamics of Green Lacewing Chrysoperla carnea Stephens. Arab Journal of Plant Protection, 41(1): 28-36. https://doi.org/10.22268/AJPP-41.1.028036 The study was carried out to evaluate toxicity and sublethal effects of lufenuron, novaluron, and lambda-cyhalothrin on natural enemies such as Chrysoperla carnea. All sub-lethal concentrations caused a significant decrease in oviposition period, total fecundity, longevity, and total life span of C. carnea compared to the control. Maximum and minimum mean lifespan of C. carnea individuals were observed in the untreated group and LC30 concentration of novaluron. Total fecundity varied from 153.47 offspring/individual in treatment with LC30 novaluron to 300.12 offspring/individual in the control treatment. The highest value for intrinsic and finite rate of increase (r, λ) was obtained by the concentration of lambda-cyhalothrin. The net reproduction rate (R0) reached its lowest level in novaluron treatment. As a result, the effects of sublethal concentrations of lufenuron, novaluron, and lambda-cyhalothrin on C. carnea were assessed and discussed to design improved integrated management programs. Keywords: Integrated pest management, side effects, aphidophagous predators, natural enemies.

High resistance levels in brazilian Plutella xylostella populations: needs for adjustments in field concentration

ABSTRACT Plutella xylostella cause severe damage on cruciferous plants all over the world. Farmers in several regions of Brazil report increasing inefficiency of chemical control, even when using high insecticide concentrations. We evaluate here the susceptibility of brazilian diamondback moth populations to the Premio® (Chlorantraniliprole), Dipel® (Bacillus thuringiensis var. kurstaki) and Lannate® BR (Oxime Methylcarbamate) insecticides, frequently used in Brazil. Susceptibility bioassays with five field-collected and two laboratory diamondback moth populations were conducted with increasing concentrations of insecticides up to ten times above the recommended concentration. Extremely high and region-dependent resistances were found in field populations against Chlorantraniliprole and B. thuringiensis, with Resistance Ratios up to 370.0 times for the Camocim de São Felix population. For Oxime Methylcarbamate, we were not able to do Probit analyses for the field populations because of very low mortality rates. Laboratory populations showed resistance to the three tested insecticides with all LC50 concentrations exceeding the recommended doses by at least 3 times. Our results show strong and variable resistance to the three tested insecticides according to the region of origin. To maintain efficient pest control in a large country like Brazil, local levels of resistance need therefore to be monitored by the authorities and reassessment and adjustments of regional doses of insecticides should be implemented as a public policy, to prevent massive spread of insecticides in the field, as well as increases in cases of resistance.

Impact of caffeic acid on growth, development and biochemical physiology of insect pest, Spodoptera litura (Fabricius)

The tobacco cutworm, Spodoptera litura (Fabricius) is a serious cosmopolitan pest that attacks several economically important crops such as maize, sorghum, chickpea, pigeon pea, cotton, tobacco and sunflower. It has developed resistance to most pesticides resulting in its continual outbreak. The effect of caffeic acid on second instar larvae of S. litura was evaluated by carrying out bioassays, nutritional assays, immune assays and biochemical assays with phenolic acids. Bioassays carried out with second instar larvae of S. litura showed growth inhibiting effects of various concentrations (5 ppm, 25 ppm, 125 ppm, 625 ppm and 3125 ppm) of caffeic acid on S. litura in comparison to control. A significant increase in mortality as well as an increased development time was observed with increase in the concentration of caffeic acid. A decrease in nutritional indices, including relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of ingested food (ECI), efficiency of conversion of digested food (ECD), and approximate digestibility (AD), indicated that dietary caffeic acid also negatively impacted the nutritional physiology of S. litura larvae. Caffeic acid has a significant impact on the immunological response of S. litura larvae. As the concentration of caffeic acid increased, the overall number of hemocytes decreased. Enzymatic assays revealed a significant increase in antioxidant enzymes when S. litura larvae were given an artificial diet containing LC50 concentration of phenolic acid for an interval of 24, 48, 72 and 96 h. The levels of oxidative stress markers (hydrogen peroxide, protein carbonyl and lipid peroxide) were also significantly enhanced in S. litura larvae after treatment with phenolic acid. According to our study, caffeic acid can be employed as a substitute for traditional insecticides to reduce the population of S. litura.

The Comparative Toxicity, Biochemical and Physiological Impacts of Chlorantraniliprole and Indoxacarb on Mamestra brassicae (Lepidoptera: Noctuidae).

The cabbage moth, Mamestra brassicae, is a polyphagous pest that attacks several crops. Here, the sublethal and lethal effects of chlorantraniliprole and indoxacarb were investigated on the developmental stages, detoxification enzymes, reproductive activity, calling behavior, peripheral physiology, and pheromone titer of M. brasssicae. Methods: To assess pesticide effects, the second instar larvae were maintained for 24 h on a semi-artificial diet containing insecticides at their LC10, LC30, and LC50 concentrations. M. brassicae was more susceptible to chlorantraniliprole (LC50 = 0.35 mg/L) than indoxacarb (LC50 = 1.71 mg/L). A significantly increased developmental time was observed with both insecticides at all tested concentrations but decreases in pupation rate, pupal weight, and emergence were limited to the LC50 concentration. Reductions in both the total number of eggs laid per female and the egg viability were observed with both insecticides at their LC30 and LC50 concentrations. Both female calling activity and the sex pheromone (Z11-hexadecenyl acetate and hexadecenyl acetate) titer were significantly reduced by chlorantraniliprole in LC50 concentration. Antennal responses of female antennae to benzaldehyde and 3-octanone were significantly weaker than controls after exposure to the indoxocarb LC50 concentration. Significant reductions in the enzymatic activity of glutathione S-transferases, mixed-function oxidases, and carboxylesterases were observed in response to both insecticides.

Hormesis effects of sulfoxaflor on Aphis gossypii feeding, growth, reproduction behaviour and the related mechanisms

Sulfoxaflor, an important alternative insecticide in integrated pest management (IPM) strategies, can effectively control sap-feeding insect pests such as Aphis gossypii. Although the side effects of sulfoxaflor have recently attracted widespread attention, its toxicological characteristics and mechanisms are still largely undefined. Therefore, the biological characteristics, life table and feeding behaviour of A. gossypii were studied to evaluate the hormesis effect of sulfoxaflor. Then, the potential mechanisms of induced fecundity associated with the vitellogenin (Ag. Vg) and vitellogenin receptor (Ag. VgR) genes were investigated. Although the LC10 and LC30 concentrations of sulfoxaflor significantly reduced the fecundity and net reproduction rate (R0) of the directly exposed sulfoxaflor-resistant and susceptible aphids, hormesis effects on fecundity and R0 were observed in the F1 generation of Sus A. gossypii when the parental generation was exposed to the LC10 of sulfoxaflor. Moreover, the hormesis effects of sulfoxaflor on phloem feeding were observed in both A. gossypii strains. Additionally, enhanced expression levels and protein content of Ag. Vg and Ag. VgR were observed in progeny generations when F0 was subjected to the trans- and multigenerational sublethal sulfoxaflor exposure. Therefore, sulfoxaflor-induced resurgence might occur in A. gossypii after exposure to sublethal concentrations. Our study could contribute to a comprehensive risk assessment and provide convincing reference to optimize sulfoxaflor in IPM strategies.

Synthesis and characterization of different complexes derived from Schiff base and evaluation as a potential anticancer, antimicrobial, and insecticide agent

The condensation of (1H-benzimidazole-2-yl) methanamine, with 2-hydroxy naphthaldehyde lead to Schiff base ligand (H2L) (1). This was later reacted with metal salts (ZnCl2, CrCl3·6H2O, and MnCl2·4H2O) to afford the corresponding metal complexes. Biological activity findings indicate that the metal complexes have promising activity against Escherichia coli and Bacillus subtilis and modest activity against Aspergillus niger. The in vitro anticancer activities of Zn (II), Cr (III), and Mn (II) complexes were investigated and the best results were observed with Mn (II) complex as the most potent cytotoxic agent toward human cell lines colorectal adenocarcinoma HCT 116, hepatocellular carcinoma HepG2 and breast adenocarcinoma MCF-7 with 0.7, 1.1 and 6.7 μg of inhibitory concentration IC50 values respectively. Consequently, the Mn (II) complex and ligand were docked inside the energetic site of ERK2 and exhibited favorable energy for binding. The investigation of biological tests towards mosquito larvae indicates that Cr (III) and Mn (II) complexes manifest strong toxicity against Aedes aegypti larvae with 3.458 and 4.764 ppm values of lethal concentration LC50, respectively.