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PubMed2002

Evaluation of take-home organophosphorus pesticide exposure among agricultural workers and their children.

We analyzed organophosphorus pesticide exposure in 218 farm worker households in agricultural communities in Washington State to investigate the take-home pathway of pesticide exposure and to establish baseline exposure levels for a community intervention project. House dust samples (n = 156) were collected from within the homes, and vehicle dust samples (n = 190) were collected from the vehicles used by the farm workers to commute to and from work. Urine samples were obtained from a farm worker (n = 213) and a young child (n = 211) in each household. Dust samples were analyzed for six pesticides, and urine samples were analyzed for five dialkylphosphate (DAP) metabolites. Azinphosmethyl was detected in higher concentrations (p < 0.0001) than the other pesticides: geometric mean concentrations of azinphosmethyl were 0.53 micro g/g in house dust and 0.75 micro g/g in vehicle dust. Dimethyl DAP metabolite concentrations were higher than diethyl DAP metabolite concentrations in both child and adult urine (p < 0.0001). Geometric mean dimethyl DAP concentrations were 0.13 micro mol/L in adult urine and 0.09 micro mol/L in child urine. Creatinine-adjusted geometric mean dimethyl DAP concentrations were 0.09 micro mol/g in adult urine and 0.14 micro mol/g in child urine. Azinphosmethyl concentrations in house dust and vehicle dust from the same household were significantly associated (r2 = 0.41, p < 0.0001). Dimethyl DAP levels in child and adult urine from the same household were also significantly associated (r2 = 0.18, p < 0.0001), and this association remained when the values were creatinine adjusted. The results of this work support the hypothesis that the take-home exposure pathway contributes to residential pesticide contamination in agricultural homes where young children are present.

Adult↗

PubMed2004

Synergism of insecticides provides evidence of metabolic mechanisms of resistance in the obliquebanded leafroller Choristoneura rosaceana (Lepidoptera: Tortricidae).

The interactions between six insecticides (indoxacarb, cypermethrin, chlorpyrifos, azinphosmethyl, tebufenozide and chlorfenapyr) and three potential synergists, (piperonyl butoxide (PBO), S,S,S-tributyl phosphorotrithioate (DEF) and diethyl maleate (DEM)) were studied by dietary exposure in a multi-resistant and a susceptible strain of the obliquebanded leafroller, Choristoneura rosaceana (Harris). The synergists did not produce appreciable synergism with most of the insecticides in the susceptible strain. Except for tebufenozide, PBO synergized all the insecticides to varying degrees in the resistant strain. A very high level of synergism by PBO was found with indoxacarb, which reduced the resistance level from 705- to 20-fold when PBO was administered alone and to around 10-fold when used in combination with DEF. DEF also synergized indoxacarb, cypermethrin, chlorpyrifos, azinphosmethyl and tebufenozide in the resistant strain. DEM produced synergism of indoxacarb, chlorpyrifos, azinphos-methyl and chlorfenapyr in the resistant strain. DEM was highly synergistic to cypermethrin, and to some extent to tebufenozide in both the susceptible and resistant strains equally, implying that detoxification by glutathione S-transferases was not a mechanism of resistance for these insecticides. The high level of synergism seen with DEM in the case of cypermethrin may be due to an increase in oxidative stress resulting from the removal of the antioxidant, glutathione. These studies indicate that enhanced detoxification, often mediated by cytochrome P-450 monooxygenases, but with probable esterase and glutathione S-transferase contributions in some cases, is the major mechanism imparting resistance to different insecticides in C. rosaceana.

Animals↗

PubMed1991

The effect of certain intrinsic and extrinsic variables on the acute toxicity of selected organophosphorus insecticides to the mummichog, Fundulus heteroclitus.

The acute toxicity of two organophosphorus (OP) insecticides, azinphosmethyl and acephate, was evaluated in the mummichog, Fundulus heteroclitus. In addition, the effects of certain intrinsic (sex) and extrinsic (salinity and multiple toxicant interraction) variables on the toxic response were also investigated. Azinphosmethyl was by far the most toxic of the two OP insecticides with a 96h LC50 approximately 100,000 x lower than that for acephate. Slight sex differences were observed in the sensitivity of mummichogs to each of the OP insecticides with male fish being marginally more sensitive. Significant effects of low salinity stress were observed only with acephate exposure and, in this case, low salinity appeared to be slightly protective. In general, all of the insecticide mixtures (azinphosmethyl/endosulfan, azinphosmethyl/fenvalerate and acephate/fenvalerate) tested exhibited simple additive toxicity.

Animals↗

PubMed2000

Baseline susceptibility to imidacloprid and cross resistance patterns in Colorado potato beetle (Coleoptera: Chrysomelidae) populations.

During 1995-1998, we tested 134 geographically discrete populations of Colorado potato beetle, Leptinotarsa decemlineata (Say), from the United States, Canada, Germany, France, and Poland for susceptibility to imidacloprid. Neonates were assayed on potato-based agar diet incorporated with imidacloprid and exposed on filter paper to esfenvalerate, azinphosmethyl, and carbofuran to characterize cross-resistance. In all 4 yr, Long Island populations were the most tolerant to imidacloprid, with LC50s ranging up to 29 times higher than the most susceptible populations. Responses to imidacloprid did not change significantly on farms where populations were assayed over time, except for those from Long Island, which doubled in overall tolerance to imidacloprid since 1995. Much of this tolerance was already present before imidacloprid was used on Long Island. Correlative analysis of the populations tested over the 4 yr indicated positive cross-resistance patterns with esfenvalerate and azinphosmethyl. This response was probably caused by preexisting metabolic and excretion mechanisms selected by previous exposure. There was no significant pattern of cross-resistance with carbofuran or bensultap. Regression slopes were also significantly negatively correlated with LC50 values for imidacloprid, indicating higher heterogeneity, which could lead in further resistance development. We discuss the relative sensitivity of diet-incorporated assays with neonates compared with other bioassay studies. Based on a pooled group of susceptible populations tested in 1995, a baseline LC50 of 0.39 ppm and a discriminating concentration of 8 ppm were suggested to detect early stages of resistance in "suspect" populations. We also suggest application strategies for imidacloprid that reduce selection pressure.

Animals↗

PubMed2004

Multipathway organophosphorus pesticide exposures of preschool children living in agricultural and nonagricultural communities.

Environmental measurements of organophosphorus (OP) pesticides were conducted in the homes of 13 children, who lived either in the Seattle metropolitan area or in the agricultural region of Washington State, to ascertain exposure through multiple pathways. Each home was sampled for two 24-h periods during two seasons, summer and fall. Samples included 24-h indoor air, drinking water, soil, house dust, and hand and toy wipes and 24-h duplicate diets. At least one OP pesticide was found in each of the matrices sampled except for drinking water. Half of the indoor air samples contained detectable levels of chlorpyrifos or diazinon. Detectable levels of diazinon and azinphosmethyl in house dust were found in most of the agricultural homes, whereas only diazinon was found in the Seattle homes in the summer. Quantifiable chlorpyrifos and azinphosmethyl were found on either agricultural children's hands or their toys. These findings suggest different exposure pathways for children living in agricultural and nonagricultural regions.

Agriculture↗

PubMedDate not supplied

Assessment of organophosphorous pesticide exposures in the diets of preschool children in Washington State.

Twenty-four hour duplicate diet sampling was employed to investigate dietary pesticide exposures of children aged 2 to 5 years. Duplicate diets were collected from seven children living in the Seattle metropolitan area and six children living in Chelan and Douglas counties in Central Washington. Diet samples were collected from each child in the summer and again in the fall, and total daily diets were divided into four food categories: fresh fruits and vegetables, beverages, processed foods, and dairy products. A total of 88 individual food category samples were collected and analyzed for 15 organophosphorous (OP) pesticides. Three of the 13 children had no detectable OP pesticides in either of their diet samples, and 14 of the 26 duplicate diets did not contain detectable levels of OP pesticides. Sixteen individual food category samples contained detectable levels of at least one OP pesticide and two of these samples contained detectable levels of two OP pesticides. Of the 15 targeted pesticides, 6 were detected: azinphosmethyl, chlorpyrifos, malathion, methidathion, methyl parathion, and phosmet. Azinphosmethyl was detected most frequently (10% of all samples), particularly in samples containing apples or apple juice. The fresh fruits and vegetable category had the most frequent pesticide determinations, followed by beverages. OP pesticides were not present at detectable levels in any of the dairy samples. Malathion was the only OP pesticide detected in processed food samples, appearing in 4 of the 26 samples (15%). No detections were above the legal tolerances for residues on produce, however the acute population-adjusted reference dose (aPAD) for chlorpyrifos exposure of 1.7 microg/kg/day was exceeded by one subject during one sampling event. This subject's cumulative daily dose of chlorpyrifos equivalents was estimated to be 2.5 microg/kg/day.

Biomarkers↗

PubMed2005

Stage-specific control of grape berry moth, Endopiza viteana (Clemens) (Lepidoptera: Tortricidae), by selective and broad-spectrum insecticides.

The insect growth regulators (IGRs) tebufenozide and methoxyfenozide and the broad-spectrum insecticides azinphosmethyl, carbaryl, and fenpropathrin were compared for their activity against adult, egg, and larval stages of the grape berry moth, Endopiza viteana (Clemens) (Lepidoptera: Tortricidae), under laboratory and vineyard conditions. Adult mortality was not affected by exposure to field-equivalent rates of tebufenozide or methoxyfenozide on grape clusters, whereas all the broad-spectrum compounds significantly reduced adult survival, compared with the untreated controls. Surviving adult moths laid significantly more eggs on berries treated with the IGRs than on berries treated with any of the broad-spectrum insecticides. Survival of these eggs through to late larval and pupal stages was significantly lower on methoxyfenozide-treated grapes than on untreated grapes, and no pupae were found when grapes were treated with azinphosmethyl or fenpropathrin. Neither of the growth regulator insecticides limited egg eclosion or larval development by E. viteana when insecticides were applied before egg laying, whereas broad-spectrum insecticides were effective against both eggs and neonates at this timing. When applied after egg eclosion, all insecticide treatments significantly reduced survival of grape berry moth larvae. Under vineyard conditions, berries with 1-d-old residues of tebufenozide or methoxyfenozide received more E. viteana eggs than berries treated with broad-spectrum compounds. After aging for 7 or 14 d, no significant effects on E. viteana survival were detected among treatments. Whereas broad-spectrum insecticides provide control of multiple life stages of E. viteana, integration of tebufenozide or methoxyfenozide into vineyard management programs for control of this pest will be most successful if applications are timed for egg hatch.

Animals↗

PubMed2005

Development, oviposition, and mortality of Neoseiulus fallacis (Acari: Phytoseiidae) in response to reduced-risk insecticides.

Eight reduced-risk insecticides (acetamiprid, thiamethoxam, imidacloprid, thiacloprid, methoxyfenozide, pyriproxyfen, indoxacarb, and spinosad) and three conventional insecticides (azinphosmethyl, fenpropathrin, and esfenvalerate) were tested against Neoseiulus fallacis (Garman) (Acari: Phytoseiidae), the most abundant predacious mite in North Carolina apple (Malus spp.) orchards. To assess the effect of insecticides on development and mortality of N. fallacis immatures, 12-h-old eggs were individually placed on bean leaf disks previously dipped in insecticide solutions. Tetranychus urticae Koch (Acari: Tetranychidae) females were added as a food source. None of the reduced-risk insecticides significantly affected immature N. fallacis compared with the control; however, the pyrethroids esfenvalerate and fenpropathrin were highly toxic to immatures. To evaluate the effect of insecticides on mortality and oviposition of adult N. fallacis, 7- to 8-d-old females were confined on insecticide-treated bean leaves with Malephora crocea (Aizoaceae) pollen added as a food source. Spinosad resulted in the highest mortality, whereas azinphosmethyl, acetamiprid, fenpropathrin, and imidacloprid were moderately toxic, and mortality from esfenvalerate, indoxacarb, thiacloprid, methoxyfenozide, pyriproxyfen, and thiamethoxam did not differ significantly from the control. Oviposition was affected in a similar manner, with the exception of acetamiprid that did not affect oviposition, and thiamethoxam that reduced oviposition.

Animals↗

PubMed2001

Spider fauna in apple ecosystem of western Oregon and its field susceptibility to chemical and microbial insecticides.

Twelve families, 26 genera, and 30 identifiable spider species were found in surveys conducted in apple orchards of western Oregon. The Salticidae, Linyphiidae, Clubionidae, Philodromidae, and Theridiidae comprised 85.56% ofthe total spiders collected. The most common species in order of abundance were Metaphidippus aeneolus Curtis, Spirembolus mundus Chamberlin & Ivie, Cheiracanthium inclusum (Hentz), Philodromus spectabilis Keyserling, Eris marginata (Walckenaer), and Theridion lawrencei Gertsch & Archer. Individuals of these species were collected in 50-60% of the samples and were most abundant in the month of August. The Bacillus thuringiensis-based insecticides, DiPel (100 Million International Units/100 liters) and MVP (250 ml/100 liters), summer oil (0.5-1.0 liter/100 liters), the insect growth regulator (IGR) diflubenzuron (3-12 g/100 liters), and organophosphate Phosmet (6-60 g/100 liters) were generally harmless (P > 0.05) to these spider species. Full field rates of organophosphate azinphosmethyl (25 g/100 liters) and carbamate carbaryl (60 g/100 liters) were slightly to moderately harmful (25-75% mortality). These insecticides at reduced rates (azinphosmethyl 2.5-5.0 g and carbaryl 12 g/100 liters) applied alone or in combination with DiPel and MVP, had a negligible effect. Full rates of pyrethroids esfenvalerate (2.5 g/100 liters) and permethrin (4.0 g/100 liters) were moderately to highly harmful (50-75% mortality) and their reduced rates (esfenvalerate 0.25-0.50 g and permethrin 0.4-0.8 g/100 liters) were selective to the spiders.

Agriculture↗

PubMed2001

Purification and characterization of a phosphoric triester hydrolase from the tufted apple bud moth, Platynota idaeusalis (Walker).

Whole body homogenates from azinphosmethyl-resistant fifth instars of the tufted apple bud moth demonstrated 11.8-fold elevated phosphoric triester hydrolase (methyl paraoxonase) activity as compared to susceptible insects of the same species. Elevated phosphoric triester hydrolase (PTEH) activity associated with resistance was also found in the Colorado potato beetle but not in the German cockroach or tobacco budworm. Phosphoric triester hydrolase activity in the tufted apple bud moth was minimal in resistant and susceptible third instars and in adult males and females and was highest in whole body homogenates and in the alimentary canal of resistant fifth instars. A microtiterplate assay was developed, which successfully diagnosed resistance in individual fifth instars based on increased phosphoric triester hydrolase (methyl paraoxonase) activity. Phosphoric triester hydrolase was purified 289-fold from fifth instars of resistant bud moths, but any additional resolution resulted in the loss of enzyme activity. Phosphoric triester hydrolase demonstrated an apparent molecular weight of 41,000 with an isoelectric point of 5.28. Methyl paraoxonase activity was increased by calcium, cobalt, manganese, and octylthio-1,1,1-trifluoro-2-propanone and decreased by mercury, phosphate ions, tin, and ethylenediaminetetraacetic acid. Iron, potassium chloride, lithium, magnesium, sodium chloride, and lead had no effect.

Animals↗

PubMed2004

Organophosphorous and organochlorine pesticides affect human placental phosphoinositides metabolism and PI-4 kinase activity.

The objective of this work was to describe the effect of organophosphorous and organochlorine pesticides on phosphoinositides metabolism in human placenta. Pesticides concentration (10 microM) was used for in vitro incubations of cell-free homogenates labelled with (32)P orthophosphate. Heptachlor (HC) and dichloro-diphenyl-trichloroethane (o-p' DDT) increased phosphatidyl-inositol, phosphatidylinositolphosphate, and phosphatidyl-inositolbiphosphate phosphorylation while azinphosmethyl (AM) increased phosphatidylinositolbiphosphate labeling. Decreased (32)P incorporation in phosphatidylinositol was found with phosmet (PM), AM, and chlorpyriphos (CHL). The effects of these xenobiotics on PI4-kinase activity using different subcellular fractions were also examined. Both type of pesticides affected the postmembrane supernatant enzyme activity. A biphasic effect on membrane and nuclear PI4-kinase activity was seen with HC. The strongest effect found was seen with o-p' DDT in nuclear kinase activity while substantial changes were also observed in membrane. These data demonstrate the sensitivity of human placental PI4-kinase to pesticides currently found in human tissues and suggest deleterious consequences in different processes regulated by 4-phosphoinositides.

1-Phosphatidylinositol 4-Kinase↗

PubMed1995

Effects of azinphos-methyl on the reproductive success of the bluegill sunfish, Lepomis macrochirus, in littoral enclosures.

Adult bluegills were exposed to a single application of azinphosmethyl in 12 littoral enclosures in a northern Minnesota pond. Responses measured were adult behavior and spawning, embryo hatchability, larval survival until swim-up, young-of-year (Y-O-Y) growth, and total biomass. Four enclosures each were treated at 1.0 and 4.0 micrograms/liter and four remained untreated. The half-life of azinphos-methyl was 2.3 and 2.4 days at each of the two treatment levels, respectively. Quantifiable residues remained in the water for 8 days. Concentrations of 4.0 or 1.0 microgram/liter did not cause any significant long-term (63 day) effects on bluegill reproduction, embryo hatchability, larval survival, growth, or biomass. Although important bluegill prey such as copepod nauplii and cladocerans were significantly or greatly reduced by Day 7 following treatment, they recovered to levels equal to or greater than some of the control enclosures by Day 35. The apparent lack of significant long-term effects on reproductive success can be partially explained by the relatively short half-life of azinphos-methyl in littoral enclosures.

Animals↗

PubMed2002

Acute toxicity of drainage ditch water from a Washington State cranberry-growing region to Daphnia pulex in laboratory bioassays.

High concentrations of organophosphorous insecticides resulting from cranberry bog applications were detected in the Grayland Drainage Ditch (GDD) system in Grayland, Washington State, during the 1994-1996 Washington State Department of Ecology Pesticide Monitoring Program. This drainage ditch system drains cranberry bogs and enters the Pacific Ocean via the North Cove and Supon Inlet. Concerns about the impact of these pesticides on human and environmental health led to this investigation of the potential impact on an indicator species, Daphnia pulex. To determine the toxic effects of multiple pesticides entering the GDD, standardized laboratory toxicity tests with D. pulex were conducted concurrently with the Washington State Department of Ecology pesticide sampling. Concentrations of three insecticides, diazinon, chlorpyrifos, and azinphosmethyl, were the highest ever detected in state waters. The GDD water was found to cause acute toxicity in 33% of the laboratory bioassays conducted. Regression analysis, however, detected a poor correlation between total insecticide detected and percentage mortality of D. pulex at the two drainage ditch sites studied, Grays Harbor County site and the Pacific County site. However, the relationship between mortality of D. pulex and detected concentrations of diazinon and chlorpyrifos were significant. Sampling schedules for chemical analysis and bioassay testing appear to be the primary reason that statistical analysis failed to correlate mortality with detected OP pesticide concentrations. Grab samples used in toxicity testing may over- or underestimate actual concentrations of contaminants present in the system being studied.

Agriculture↗

PubMed2005

Correlation between 96-h mortality and 24-h acetylcholinesterase inhibition in three grass shrimp larval life stages.

Three life stages of larval grass shrimp were tested to determine whether acetylcholinesterase (AChE) activity expressed as 24-h sublethal effect endpoints (EC20 and EC50) could be used to predict 96-h mortality (lowest observable effect concentration (LOEC) and LC50) for shrimp exposed to three organophosphate insecticides. With regard to mortality, newly hatched larvae and 18-day-old larvae were the most sensitive in the malathion and azinphosmethyl exposures. In the chlorpyrifos exposures, newly hatched larvae and postlarvae were the most sensitive life stages. Results of the 24-h AChE inhibition tests showed that newly hatched larvae were generally more sensitive in the three organophosphate exposures. A regression analysis of the EC50's and LC50's yielded the strongest correlation with R2=0.987 (correlation coefficient=0.994 and 95% confidence intervals 0.969-0.999). The LOEC/EC20 relationship yielded R2=0.962. For these grass shrimp life stages and pesticides, sublethal effect endpoints could be used as a predictor of 96-h mortality.

Acetylcholinesterase↗

PubMed2001

Rainfall-induced sediment and pesticide input from orchards into the Lourens River, Western Cape, South Africa: importance of a single event.

Rainfall-induced runoff transported sediments and pesticides into the Lourens River and its tributaries during a 28.8-mm rainstorm in mid-December 1998. Average 1-h peak levels of current-use insecticides applied to adjacent orchard plots were 1.5 micrograms l-1 azinphos-methyl, 0.2 microgram l-1 chlorpyrifos and 2.9 micrograms l-1 total endosulfan (alpha, beta, S) in the river itself. Respective average 1-h pesticide levels associated with suspended particles were 1247, 924 and 12,082 micrograms kg-1, along with 980 micrograms kg-1 of prothiofos. Total suspended solids increased during runoff from 32 to 520 mg l-1. The contaminated edge-of-field runoff entered the river via the tributaries directly bordering the orchard-growing areas. Increased concentrations of azinphos-methyl and prothiofos associated with suspended sediments were demonstrated to persist for about 3.5 months without any further input in one of the tributaries. This illustrates that the short-term exposure has the potential to result in long-term contamination of surface waters. In terms of chemical load during the 1-h peak discharge period, the single rainfall event caused a loss of 173 g h-1 azinphosmethyl, 55 g h-1 chlorpyrifos, 740 g h-1 total endosulfan (alpha, beta, S) and 41 g h-1 prothiofos. Levels of contamination were extremely high; they exceed the national water quality standards and those established by the US EPA. A comparison with standard toxicity data and 24-h LC50 s for the local amphipod species Paramelita nigroculus, obtained during this study, indicates that the concentrations found in the river may result in acute toxic effects on aquatic invertebrates and fishes. A probability analysis of 10-y rainfall data revealed that the frequency of a similar storm event occurring within the main spraying season is 1.7 y-1.

Agriculture↗

PubMed2002

Fate and environmental impact of pesticides in plastic mulch production runoff: field and laboratory studies.

Concentrations of copper, azinphosmethyl, chlorothalonil, and endosulfan sulfate ranged from less than 1 to greater than 1000 microg/L in runoff from tomato plastic mulch production. When this runoff entered local creeks, the copper concentration was as high as 22 microg/L, which exceeded the measured larval clam LC50 values of 21 and 12 microg/L Cu at 96 and 192 h, respectively. A greenhouse scale investigation of copper and toxicity demonstrated that sedimentation reduced total copper concentration in runoff by 90%, although the dissolved copper concentration was unchanged, averaging 139 +/- 55 microg/L. When runoff was applied to marine mesocosms containing grass shrimp and mummichog fish, unsettled runoff produced the greatest mortality, although even settled runoff caused more mortality than that in the control mesocosm receiving runoff without added copper. Desorption of soil-sorbed copper occurred quickly in saline water and contributed to toxicity. Copper toxicity in runoff can be reduced, but not eliminated, by sedimentation.

Agriculture↗

PubMed1997

Estimating pesticide exposure in tidal streams of Leadenwah Creek, South Carolina.

This article estimates the potential exposure of estuarine organisms to two pesticides (azinphosmethyl and fenvalerate) in a tidal stream of Leadenwah Creek near the Edisto River, South Carolina, during four runoff episodes. Exposure is calculated from simulation runs of the one-dimensional transport equation solved by an implicit finite difference method. Calibration was done for each episode by adjusting three conditions (runoff starting time, duration, and flow) and a correction to the dispersion coefficient in order to match the continuously measured salinity transients. First-order rate constants used by the fate component were calculated from half-life values reported in the literature. Baseline scenarios for each episode and each pesticide were derived by using the same conditions obtained in the salinity runs and adjusting the pesticide loading in order to mimic the few data points of measured pesticide concentrations. In all baseline scenarios, pesticide concentration rises following the initial burst of runoff (also noticeable as an abrupt drop in salinity) and then oscillates, forced by the tidal cycle. These oscillations are dominated by transport, while fate imposes a secular decaying trend. Ten additional scenarios for each episode were obtained from the baseline scenario by randomly varying three pesticide load parameters (starting time and duration of runoff, and pesticide discharge) using a Latin hypercubes design. Two exposure metrics were calculated from the simulated and the measured pesticide concentration: maximum and time average, which was obtained by integrating the curve and dividing by the time period. The metrics calculated from the baseline runs are relatively close to the data-derived metrics, because the baseline runs attempted to mimic the data. For each one of the two metrics and all pesticide-episode combinations, several statistics of the set of 11 scenarios were also calculated: minimum and maximum, mid-range, mean, standard deviation, and median. The mean +/- standard deviation interval of the simulation-derived value consistently brackets the data-derived value for the maximum metric, but not for the time-average metric. This may indicate that even if the maximum value is correctly captured in the field sample, the time-average exposure could be in error when calculated directly from the field data due to undersampling of the pesticide time series. The methodology developed here attempts to reconstruct the possible exposure from the sparse sampling of the pesticide concentration during the runoff episodes; only when the number of field samples is high and regularly spaced is it possible to have confidence in the reconstruction of the curve. The shape of the curve cannot be inferred from the field measurements alone; as expected, tidal movement makes the pesticide concentration swing up and down. This result has important implications because the biological community would be subject to repetitive pulses of exposure to the chemicals. The baseline simulations can be used to derive a pulse-exposure metric by calculating the sum of ratios of the time average of the threshold-exceeding concentrations to the time average of the toxic threshold during intervals of above-threshold concentration. This metric is species specific and extrapolates laboratory toxicity data in order to compare pulse exposure to mortality rates measured in the field.

Azinphosmethyl↗

PubMed2005

Role of neonicotinyl insecticides in Washington apple integrated pest management. Part I. Control of lepidopteran pests.

Three neonicotinyl insecticides, acetamiprid, thiacloprid and clothianidin, were evaluated for their impact on four species of lepidopteran pests of apple in Washington, the codling moth, Cydia pomonella (L.), the Pandemis leafroller, Pandemis pyrusana Kearfott, and the obliquebanded leafroller, Choristoneura rosaceana (Harris), and Lacanobia subjuncta (Grote & Robinson). None of the neonicotinyl insecticides demonstrated sufficient activity against P. pyrusana, C. rosaceana, or L. subjuncta to warrant field trials. Conversely, all had some activity against one or more stages of C. pomonella. Acetamiprid was highly toxic to larvae in laboratory bioassays, and had relatively long activity of field-aged residues (21 days). It also showed some toxicity to C. pomonella eggs (via topical exposure) and adults. Acetamiprid provided the highest level of fruit protection from C. pomonella attack in field trials conducted over five years in experimental orchards with extremely high codling moth pressure. Thiacloprid performed similarly in bioassays, but fruit protection in field trials was slightly lower than acetamiprid. Clothianidin showed moderate to high toxicity in bioassays, depending on the C. pomonella stage tested, but poor fruit protection from attack in field trials. None of the neonicotinyl insecticides were as toxic to larvae or effective in protecting fruit as the current standard organophosphate insecticide used for C. pomonella control, azinphosmethyl. However, both acetamiprid and thiacloprid should provide acceptable levels of C. pomonella control in commercial orchards where densities are much lower than in the experimental orchards used for our trials. The advantages and disadvantages of the neonicotinyl insecticides as replacements for the organophosphate insecticides and their role in a pest management system for Washington apple orchards are discussed.

Agriculture↗