The Effect of Residual Pesticide Application on Microbiomes of the Storage Mite Tyrophagus putrescentiae.

Arthropods can host well-developed microbial communities, and such microbes can degrade pesticides and confer tolerance to most types of pests. Two cultures of the stored-product mite Tyrophagus putrescentiae, one with a symbiotic microbiome containing Wolbachia and the other without Wolbachia, were compared on pesticide residue (organophosphate: pirimiphos-methyl and pyrethroid: deltamethrin, deltamethrin + piperonyl butoxide)-containing diets. The microbiomes from mite bodies, mite feces and debris from the spent mite diet were analyzed using barcode sequencing. Pesticide tolerance was different among mite cultures and organophosphate and pyrethroid pesticides. The pesticide residues influenced the microbiome composition in both cultures but without any remarkable trend for mite cultures with and without Wolbachia. The most influenced bacterial taxa were Bartonella-like and Bacillus for both cultures and Wolbachia for the culture containing this symbiont. However, there was no direct evidence of any effect of Wolbachia on pesticide tolerance. The high pesticide concentration residues in diets reduced Wolbachia, Bartonella-like and Bacillus in mites of the symbiotic culture. This effect was low for Bartonella-like and Bacillus in the asymbiotic microbiome culture. The results showed that the microbiomes of mites are affected by pesticide residues in the diets, but the effect is not systemic. No actual detoxification effect by the microbiome was observed for the tested pesticides.

Effect of pesticide residues on simulated beer brewing and its inhibition elimination by pesticide-degrading enzyme.

Four different pesticide residues used in barley planting were selected to investigate their effects on simulated beer brewing. The influences were found to be different by varied agricultural chemicals. Among the four types of pesticides, at 25 µg/mL, triadimefon or carbendazim barely affected the brewing progress. However, ethametsulfuron-methyl and carbaryl (15 µg/mL and 2.5 µg/mL, respectively) exhibited slightly inhibition on saccharification and significantly negative impacts on yeast growth and alcohol fermentation. After pretreated by 50 µL carbaryl-degrading enzyme with the Kcat value of 2.12 s-1 at 30°C for 90 min, the negative influence on simulated beer brewing brought by carbaryl can be eliminated in the fermentation system containing 2.5 µg/mL carbaryl. The efficiency of ethanol fermentation was improved, and the removal rate of carbaryl in the brewing system was greatly accelerated. Taken together, this study suggested a potential method for solving the fermentation inhibition by pesticide residues.

Performance of IRS on malaria prevalence and incidence using pirimiphos-methyl in the context of pyrethroid resistance in Koulikoro region, Mali.

BACKGROUND: Koulikoro Health District is one of three districts of Mali where the indoor residual spray (IRS) has been implemented from 2008 to 2016. With widespread of resistance to pyrethroid, IRS was shifted from pyrethroid to pirimiphos-methyl from 2014 to 2016. The objective of this study was to assess the added value of IRS to LLINs on the prevalence of parasitaemia and malaria incidence among children under 10 years old. METHODS: A comparative study was carried out to assess the effects of pirimiphos-methyl based IRS on malaria prevalence and incidence among children from 6 months to 10 years old in selected pyrethroid resistance villages of two health districts in Mali: one where IRS was implemented in combination with LLINs (intervention area) and one with LLINs-only (control area). Two cross-sectional surveys were carried out at the beginning (June) and end of the rainy season (October) to assess seasonal changes in malaria parasitaemia by microscopy. A passive detection case (PCD) was set-up in each study village for 9 months to estimate the incidence of malaria using RDT. RESULTS: There was an increase of 220% in malaria prevalence from June to October in the control area (14% to 42%) versus only 53% in the IRS area (9.2% to 13.2%). Thus, the proportional rise in malaria prevalence from the dry to the rainy season in 2016 was 4-times greater in the control area compared to the IRS area. The overall malaria incidence rate was 2.7 per 100 person-months in the IRS area compared with 6.8 per 100 person-month in the control areas. The Log-rank test of Kaplan-Meier survival analysis showed that children living in IRS area remain much longer free from malaria (Hazard ratio (HR) = 0.45, CI 95% 0.37-0.54) than children of the control area (P < 0.0001). CONCLUSIONS: IRS using pirimiphos-methyl has been successful in reducing substantially both the prevalence and the incidence of malaria in children under 10 years old in the area of pyrethroid resistance of Koulikoro, Mali. Pirimiphos-methyl is a better alternative than pyrethroids for IRS in areas with widespread of pyrethroid resistance.

The control effect of fungicide pyraclostrobin against freckle disease of banana and its residue dynamics under field conditions.

Fungicide pyraclostrobin has been widely employed to control plant diseases by inhibiting the mitochondrial respiration of pathogenic fungi. Due to its broad spectrum, the extensive use of pyraclorstrobin was reported to cause emerging resistance on crops. Here, we evaluated the control effect of 250 g L-1 of pyrachlostrobin suspension concentrate (SC) against freckle disease (caused by Phyllosticta spp) on banana. Meanwhile, the dissipation and residue dynamics of pyraclostrobin in banana and soil under field conditions were determined by high performance liquid chromatography (HPLC) with DAD detection in different locations. The analytical method was validated using spiked samples at three levels, which indicated the recoveries ranged from 92.0% to 99.0% with relative standard deviations (RSDs) below 5%, providing a sensitive, precise and reliable method to monitor pyraclostrobin in banana fruit and soil. The dissipation of pyraclostrobine followed the first-order kinetics and its half-lives were 5.25 to 9.90 days. In addition, the terminal residues of pyraclostrobin in banana, banana sarcocarp and soil were below the maximum residue limit (MRL) (0.02 mg kg-1) after a pre-harvest interval (PHI) of 42 days, which suggesting that the use of pyraclostrobin at recommended dosages was safe to banana and the environment. In summary, we demonstrated the integrated evaluation on the disease control capacity of pyraclostrobin and its environmental behavior on banana, aiming to provide solid and basic data for the safe use of fungicide pyraclostrobin.

Assessment of boscalid and pyraclostrobin disappearance and behavior following application of effective microorganisms on apples.

The aim of this study is to assess the disappearance of boscalid (IUPAC name: 2-chloro-N-[2-(4-chlorophenyl)phenyl]pyridine-3-carboxamide) and pyraclostrobin (IUPAC name: methyl N-[2-[[1-(4-chlorophenyl)pyrazol-3-yl]oxymethyl]phenyl]-N-methoxycarbamate) residues in apple fruit, and to verify whether an organic fertilizer enriched with strains of antagonistic microorganisms can reduce pesticide residue levels. Field trials were conducted in a commercial orchard on apples of the Gloster variety, during 21 days after the treatment with Bellis 38 WG and the subsequent application of Zumba Plant formulation containing Bacillus spp., Trichoderma spp. and Glomus spp. In control samples, the decrease rate of boscalid and pyraclostrobin residue levels followed an exponential function, described by formulae Rt = 0.2824e-0.071t and Rt = 0.1176e-0.060t, with the coefficient of determination of r2 = 0.8692 and r2 = 0.9268, respectively. These levels dropped to half (t1/2) of their initial values after 9.8 and 11.5 days, respectively. The treatment with Zumba Plant resulted in a reduction in boscalid and pyraclostrobin residue levels by 52% and 41%, respectively. The results of this study are of importance for horticulture sciences and for producers of apples using plant protection products (PPPs).

Quantifying pesticide deposits and spray patterns at micro-scales on apple (Malus domesticus) leaves with a view to arthropod exposure.

BACKGROUND: Pesticides used in commercial crop systems can adversely affect non-target arthropod populations. The spatial distribution of pesticide residues is rarely studied at scales relevant to these populations. Here, we combine two methods for assessing pesticide spray deposits at spatial scales relevant to non-target arthropods found in apple orchards. Pesticide residues were determined on individual apple leaves through conventional residue analysis; water-sensitive paper was used to investigate spatial distributions in deposits at the micro-scale. We also evaluated how accurately a digital image analysis program estimated pesticide residues. RESULTS: We found that mean pesticide spray coverage on water-sensitive paper varied by up to 6.1% (95% CI 9.4%, 2.7%) within an apple orchard, and leaf residues varied by up to 0.95 (95% CI 0.54, 1.36) mg kg-1 within a tree. Leaf residues based on analytical chemistry were six times lower than pesticide deposition estimated through image analysis of water-sensitive paper, although these correlated strongly. This correlation allowed estimation of actual residues by application of a correction factor. CONCLUSION: Our method demonstrates accurate estimation of pesticide deposits at the individual leaf scale through digital analysis of water-sensitive paper and is a low-cost, rapid alternative to conventional residue analysis techniques. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of sequential exposure to water accommodated fraction of crude oil and chlorpyrifos on molecular and biochemical biomarkers in rainbow trout.

Fish can be simultaneously or sequentially exposed to various kinds of pollutants, resulting in combined effects. Polycyclic aromatic hydrocarbons induce cytochrome P450 monooxygenase 1A (CYP1A) expression, which catalyzes the conversion of the organophosphorus insecticide chlorpyrifos (CPF) into its most active derivative, CPF-oxon. CPF-oxon inhibits CYP1A and other enzymes, including carboxylesterases (CEs) and acetylcholinesterase (AChE). We studied the effects of an in vivo exposure to crude oil water accommodated fraction (WAF) followed by an ex vivo exposure of liver tissue to CPF on the expression of Cyp1a, AhR and ARNT mRNA, CYP1A protein and on the activity of biomarker enzymes in the rainbow trout (Oncorhynchus mykiss). Juvenile rainbow trout were exposed to WAF (62 µg L-1 TPH) for 48 h. Then, liver was dissected out, sliced and exposed to 20 µg L-1 CPF ex vivo for 1 h. Liver tissue was analyzed for mRNA and protein expression and for CEs, AChE, glutathione S-transferase (GST) and CYP1A (EROD) activity. WAF induced Cyp1a mRNA and CYP1A protein expression by 10-fold and 2.5-8.3-fold, respectively, with no effect of CPF. WAF induced AhR expression significantly (4-fold) in control but not in CPF treated liver tissue. ARNT mRNA expression was significantly lowered (5-fold) by WAF. CPF significantly reduced liver EROD activity, independently of WAF pre-treatment. CEs activity was significantly inhibited in an additive manner following in vivo exposure to WAF (42%) and ex vivo exposure to CPF (19%). CPF exposure inhibited AChE activity (37%) and increased GST activity (42%).

Relating High Insecticide Residues in Larval Breeding Habitats in Urban Residential Areas to the Selection of Pyrethroid Resistance in Anopheles gambiae s.l. (Diptera: Culicidae) in Akim Oda, Ghana.

The main objective of this study was to assess insecticide contamination in Anopheles breeding habitats in urban residential areas and pyrethroid susceptibility status of mosquitoes found in the habitats. A larval survey was conducted in Akim Oda between July and October 2016. The larvae that were reared to adult were used for susceptibility test against four different pyrethroid insecticides (deltamethrin 0.05%, permethrin 0.75%, cyfluthrin 0.15%, and etofenprox 0.5%). Gas chromatography was used to analyze pesticide residues in water collected from the breeding habitats. High levels of permethrin and deltamethrin plus traces of several organochlorine and organophosphate insecticides were detected in the larval-breeding habitats. None of the four pyrethroid insecticides caused more than 10% mortality. Anopheles coluzzii Coetzee & Wilkerson dominated in the study area with high frequency of kdr mutation (93.5%). We report for the first time in Ghana, high levels of pyrethroid insecticides contamination in Anopheles breeding habitats in urban residential areas where there are no major agricultural activities. The contamination is suspected to be the major cause of pyrethroid resistance in the Anopheles species. Improper disposal of old insecticide-treated net and other domestic insecticides and the use of herbicides are suspected to be the source of insecticide contamination.

The toxicological effects of some avermectins on goat liver carbonic anhydrase enzyme.

Avermectins are used worldwide as antiparasitic drugs in the field of veterinary medicine and as agricultural pesticides and insecticides. Carbonic anhydrase (CA, E.C. 4.2.1.1) is a zinc-containing metalloenzyme that catalyzes the reversible hydration of carbon dioxide (CO2 ) to yield protons (H+ ) and bicarbonate (HCO3- ). In this study, some avermectins, including abamectin, doramectin, eprinomectin, and moxidectin, were investigated for in vitro inhibitory effects on the CA enzyme purified from goat liver, which was purified (125.00-fold) using sepharose 4B-l-tyrosine-sulfanilamide affinity chromatography, with a yield of 68.27% and a specific activity of 21765.31 EU/mg proteins. The inhibition results obtained from this study showed Ki values of 0.283, 0.153, 0.232, and 0.317 nM for abamectin, doramectin, eprinomectin, and moxidectin, respectively. On the other hand, acetazolamide, well-known clinically established CA inhibitor, possessed a Ki value of 0.707 nM against goat liver CA.

Residual degradation and toxicity of insecticides against Bactrocera oleae.

Field and lab trials took place in Crete (July to September 2016), concerning the residual degradation and toxicity of seven active ingredients applied as bait sprays against the olive fruit fly. Highest residues were recorded in olive leaves for dimethoate and phosmet (~ 60 mg/kg) immediately after application (day 1+), while a threefold and fivefold reduction was observed 1 week later, respectively. Residues of pyrethroids were determined at lower levels (< 10 mg/kg) but remained almost stable for a longer period of time. Finally, thiacloprid and spinosad residues were determined at 5.81 and 0.19 mg/kg respectively (day 1+), and rapidly decreased below the LOQ. Highest toxicity against the olive fruit fly was observed just right after the application of dimethoate (100%), a-cypermethrin (80%), and L-cyhalothrin (72.92%). Although the toxicity of dimethoate was significantly reduced 1 week after the application (80%) and then minimized, toxicity of pyrethroids remained almost stable (> 60%) for the first 2 weeks and then decreased to 30-40%, which remained stable up to the end of the study (8 weeks). Concerning phosmet, its toxicity ranged from 35 to 56% for 3 weeks with no significant reduction, while spinosad presented a lower toxicity profile (50% only for 1 week). The benefits of these results in the knowledge of insecticide residues and their toxicity against olive fruit fly can be used for improving olive fruit fly control.

QSPR in forensic analysis - The prediction of retention time of pesticide residues based on the Monte Carlo method.

A method for the prediction of retention indices of pesticides using the Monte Carlo method and with optimal molecular descriptors based on local graph invariants and the SMILES notation of studied compounds has been presented. Quite satisfactory results were obtained with the proposed method, since a robust model with good statistical quality was developed. The predictive potential of the applied approach was tested and the robustness of the model was proven with different methods. The best calculated QSPR model had following statistical parameters: r2 = 0.9182 for the training set and r2 = 0.8939 for the test set. Structural indicators defined as molecular fragments responsible for the increases and decreases of gas chromatographic retention indices activity were calculated.

Why was resistance to shorter-acting pre-emergence herbicides slower to evolve?

BACKGROUND: Across several agricultural systems the evolution of herbicide resistance has occurred more rapidly to post-emergence than pre-emergence herbicides; however, the reasons for this are not clear. We used a new simulation model to investigate whether interactions between differences in order of application and weed cohorts affected could explain this historically observed difference between the herbicide groups. RESULTS: A 10 year delay in resistance evolution was predicted for a shorter-acting residual pre-emergence (cf. post-emergence), when all other parameters were identical. Differences in order of application between pre- and post-emergence herbicides had minimal effect on rates of resistance evolution when similar weed cohorts were affected. CONCLUSION: This modelling suggested that the historically observed lower levels of resistance to pre-emergence herbicides are most likely to be due to the smaller number of weed cohorts affected by many pre-emergence herbicides. The lower number of weed cohorts affected by pre-emergence herbicides necessitated the use of additional, effective control measures, thereby reducing resistance evolution. This study highlights the advantages of applying multiple control measures to each weed cohort. © 2016 Society of Chemical Industry.

The consequences of sublethal exposure to insecticide on the survivorship and mobility of Halyomorpha halys (Hemiptera: Pentatomidae).

BACKGROUND: The direct lethal effects of conventional and organic insecticides have been investigated thoroughly for all life stages of Halyomorpha halys. However, the sublethal effects of insecticides on the behavior of H. halys have not been well documented. Our aims were to evaluate the impact of a brief 5 min exposure to residues of bifenthrin, dinotefuran, methomyl, thiamethoxam and thiamethoxam + λ-cyhalothrin on survivorship, horizontal and vertical movement, and flight capacity of adult H. halys under laboratory conditions. RESULTS: Over half of the insecticide-exposed adults were classified as affected, moribund or dead after the 5 min exposure, compared with only 6% of the adults in the water-only control. We found that the horizontal movement, vertical climbing and flight capacity of adults exposed to insecticides were decreased by 20-60% overall relative to the water-only control. The most lethal insecticide was bifenthrin. CONCLUSION: Many insecticide-exposed H. halys adults retained significant mobility and flight capacity, with flight most pronounced immediately after exposure. These results suggest that brief exposure periods to efficacious insecticides will result in high dispersal and low mortality. Therefore, management strategies that enhance the retention of H. halys on insecticide-coated surfaces should be considered to ensure that adults are exposed to a lethal dose of insecticide. © 2016 Society of Chemical Industry.

Exonuclease I-aided homogeneous electrochemical strategy for organophosphorus pesticide detection based on enzyme inhibition integrated with a DNA conformational switch.

A novel enzyme inhibition-based homogeneous electrochemical biosensing strategy was designed for an organophosphorus pesticide assay based on exploiting the resistance of a mercury ion-mediated helper probe (HP) toward nuclease-catalyzed digestion and the remarkable diffusivity difference between HPs and the mononucleotides toward a negatively charged indium tin oxide (ITO) electrode. In particular, the mercury ion-mediated T-Hg(2+)-T base pairs facilitate the HP labeled with methylene blue (MB) to fold into a hairpin structure, preventing its digestion by exonuclease I, and thus resulting in a low electrochemical response because of the large electrostatic repulsion between the negatively charged ITO electrode and the HPs. The competitive binding by a thiol group (-SH), produced in the hydrolysis reaction of acetylthiocholine (ACh) chloride with acetylcholinesterase (AChE), removes mercury ions from the base pairs, causing a nuclease-catalyzed digestion, and the subsequent electrochemical response increase due to the weak electrostatic repulsion between the product-mononucleotides and the ITO electrode. Mercury ion-mediated HPs were first designed for pesticide detection and diazinon was chosen as the model target. Under the optimal experimental conditions, the approach exhibited high sensitivity for diazinon detection with a detection limit of 0.25 µg L(-1). The satisfactory results in the determination of diazinon in real samples demonstrate that the method possesses great potential for detecting organophosphorus pesticides. This new approach is expected to promote the exploitation of mercury-mediated base pair-based homogenous electrochemical biosensors in biochemical studies and in the food safety field.

Phosphate-solubility and phosphatase activity in Gangetic alluvial soil as influenced by organophosphate insecticide residues.

An experiment was conducted under laboratory conditions to investigate the effect of four organophosphate insecticides, viz. monocrotophos, profenophos, quinalphos and triazophos at their field application rates (0.75, 1.0, 0.5 and 0.6 kg a.i.ha(-1), respectively), on the growth and activities of phosphate solubilizing microorganisms in relation to availability of insoluble phosphates in the Gangetic alluvial soil of West Bengal, India. The proliferation of phosphate solubilizing microorganisms was highly induced with profenophos (38.3%), while monocrotophos exerted maximum stimulation (20.8%) towards the solubility of insoluble phosphates in soil. The phosphatase activities of the soil (both acid phosphatase and alkaline phosphatase) were significantly increased due to the incorporation of the insecticides in general, and the augmentation was more pronounced with quinalphos (43.1%) followed by profenophos (27.6%) for acid phosphatase, and with monocrotophos (25.2%) followed by profenophos (16.1%) for alkaline phosphatase activity in soil. The total phosphorus was highly retained by triazophos (19.9%) followed by monocrotophos (16.5%), while incorporation of triazophos and quinalphos manifested greater availability of water soluble phosphorus in soil.

Unexpected effects of sublethal doses of insecticide on the peripheral olfactory response and sexual behavior in a pest insect.

Pesticides have long been used as the main solution to limit agricultural pests, but their widespread use resulted in chronic or diffuse environmental pollutions, development of insect resistances, and biodiversity reduction. The effects of low residual doses of these chemical products on organisms that affect both targeted species (crop pests) but also beneficial insects became a major concern, particularly because low doses of pesticides can induce unexpected positive--also called hermetic--effects on insects, leading to surges in pest population growth at greater rate than what would have been observed without pesticide application. The present study aimed to examine the effects of sublethal doses of deltamethrin, one of the most used synthetic pyrethroids, known to present a residual activity and persistence in the environment, on the peripheral olfactory system and sexual behavior of a major pest insect, the cotton leafworm Spodoptera littoralis. We highlighted here a hormetic effect of sublethal dose of deltamethrin on the male responses to sex pheromone, without any modification of their response to host-plant odorants. We also identified several antennal actors potentially involved in this hormetic effect and in the antennal detoxification or antennal stress response of/to deltamethrin exposure.

Pesticides and Ostreid Herpesvirus 1 Infection in the Pacific Oyster, Crassostrea gigas.

Since 2008, mass mortality outbreaks have been reported in all French regions producing Pacific oysters, and in several Member States of the European Union. These mass mortality events of Pacific oysters are related to OsHV-1 infection. They occur during spring and summer periods leaving suspect the quality of the marine environment and the role of seasonal use of pesticides associated with the arrival of freshwater in oyster rearing areas. Pesticides have been also detected in French coastal waters, especially in areas of oyster production. Using PMA real-time PCR we showed that a mixture of 14 pesticides has no effect on the integrity of virus capsids from viral suspension in the conditions tested. A contact of oysters with this pesticide mixture was related to higher mortality rates among experimentally infected animals in comparison with control ones (no previous pesticide exposure before experimental infection). We therefore suggest that pesticides at realistic concentration can exert adverse effects on Pacific oysters and causes an increased susceptibility to the viral infection in experimental conditions.

Investigating mosquito net durability for malaria control in Tanzania - attrition, bioefficacy, chemistry, degradation and insecticide resistance (ABCDR): study protocol.

BACKGROUND: Long-Lasting Insecticidal Nets (LLINs) are one of the major malaria vector control tools, with most countries adopting free or subsidised universal coverage campaigns of populations at-risk from malaria. It is essential to understand LLIN durability so that public health policy makers can select the most cost effective nets that last for the longest time, and estimate the optimal timing of repeated distribution campaigns. However, there is limited knowledge from few countries of the durability of LLINs under user conditions. METHODS/DESIGN: This study investigates LLIN durability in eight districts of Tanzania, selected for their demographic, geographic and ecological representativeness of the country as a whole. We use a two-stage approach: First, LLINs from recent national net campaigns will be evaluated retrospectively in 3,420 households. Those households will receive one of three leading LLIN products at random (Olyset®, PermaNet®2.0 or Netprotect®) and will be followed up for three years in a prospective study to compare their performance under user conditions. LLIN durability will be evaluated by measuring Attrition (the rate at which nets are discarded by households), Bioefficacy (the insecticidal efficacy of the nets measured by knock-down and mortality of mosquitoes), Chemical content (g/kg of insecticide available in net fibres) and physical Degradation (size and location of holes). In addition, we will extend the current national mosquito insecticide Resistance monitoring program to additional districts and use these data sets to provide GIS maps for use in health surveillance and decision making by the National Malaria Control Program (NMCP). DISCUSSION: The data will be of importance to policy makers and vector control specialists both in Tanzania and the SSA region to inform best practice for the maintenance of high and cost-effective coverage and to maximise current health gains in malaria control.

Effect of feeding status on mortality response of adult bed bugs (Hemiptera: Cimicidae) to some insecticide products.

Fresh and aged residual deposits of several insecticide products were tested against bed bug adults to determine if a recent bloodmeal affected their mortality response to the residues. The bed bugs with a recent bloodmeal survived significantly longer compared with the unfed ones on their exposure to fresh or aged residual deposits of chlorfenapyr and aged residual deposits of deltamethrin on a wooden substrate. Even though the survival time of fed bed bugs was significantly longer than that of unfed ones on their exposure to fresh residue of deltamethrin and aged residue of desiccant pyrethrin dust, these treatments resulted in similarly high final mortalities regardless of feeding status of the insects. Mortality responses of fed and unfed bed bugs were similar to fresh or aged residual deposits of imidacloprid + cyfluthrin combination and fresh residual deposits of desiccant pyrethrin dust. Topical application assays indicated that a recent bloodmeal significantly increased the bed bug's survival time for chlorfenapyr, but not for deltamethrin. Pyrethroid-resistant bed bugs also showed a similar increase in their survival time for chlorfenapyr after a bloodmeal. The comparison of mortality responses between fed and unfed bed bugs treated with similar amount of chlorfenapyr per fresh body weight indicated that increased body mass was not the primary cause for this bloodmeal-induced tolerance increase for chlorfenapyr. Because the surviving bed bugs can continue ovipositing, the effectiveness of chlorfenapyr residual deposits in bed bug harborages could be significantly affected by the feeding status of the adult bed bug populations.

Pesticide residues, heavy metals, and DNA damage in sentinel oysters Crassostrea gigas from Sinaloa and Sonora, Mexico.

Pesticides and heavy metals were analyzed in sentinel Crassostrea gigas oysters placed in six aquaculture sites close to a contaminated agricultural region. Each site was sampled twice. Tests revealed the presence of organochlorine (OC) pesticides in the oysters at concentrations varying from 31.8 to 72.5 µg/kg for gamma-hexachlorocyclohexane (γ-HCH); from 1.2 to 3.1 µg/kg for dichlorodiphenyldichloroethylene (4,4-DDE); from 1.6 to 2.3 µg/kg for endosulfan I; and from 1.4 to 41.2 µg/kg for endosulfan II, as well as heavy metals in concentrations that exceeded Mexican tolerance levels (405.5 to 987.8 µg/g for zinc; 4.2 to 7.3 µg/g for cadmium; and 7.2 to 9.9 µg/g for lead). Significant levels of DNA damage in oyster hemocytes were also detected. There was a significant, positive correlation between genotoxic damage and concentration of nickel or the presence of endosulfan II. Cellular viability evaluated by cytotoxic analyses was found to be high at 80%. Marked inhibition in activity of acetylcholinesterase (AChE ) and induction of glutathione S-transferase (GST) activity was noted. Data demonstrated a significant relation between AChE activity inhibition and presence of endosulfan II, γ-HCH, copper, lead, and 4,4-DDE, as well as between AChE and GST activity at different sites.