Search

The commercial multi-walled carbon nanotube (MWCNT) was carboxylated using sulphuric and nitric acid and characterized by various techniques such as scanning eletron spectroscopy, Infra-red spectroscopy and atomic force microscopy. The acid functionalized multiwalled carbon nanotube serves as the effective matrix for the sensing of carbamate pesticide namely mexacarbate. The electrochemical oxidation of mexacarbate at GCE and MWCNT/GCE follows heterogeneous electron transfer reaction. Different experimental parameters such as the effect of scan rate and pH were studied. Rotating disk electrode voltammetry studies confirms the one-electron transfer reaction. The sensor calibration plot for mexacarbamate was constructed by means of pulse technique. The acid functionalized multiwalled carbon nanotube sensor was applied to real water sample with the recovery percentage of 85-89%.

Sea urchin embryo assay was used to assess general toxicity at four wastewater treatment plant effluents of Biscay (Gorliz, Mungia, Gernika, and Galindo), and within the tested range, all the extracts showed embryo growth inhibition and skeleton malformation activities with EC50 values, in relative enrichment factor units, between 1.1-16.8 and 1.1-8.8, respectively. To identify the causative compounds, effect-directed analysis was successfully applied for the first time using a sea urchin embryo test to the secondary treatment of the Galindo effluent. To this end, two subsequent fractionation steps were performed using C18 (21 fractions) and aminopropyl columns (15 fractions). By this fractionation, the number of features detected by LC-HRMS in the raw sample was drastically reduced from 1500 to 9, and among them, two pesticides (mexacarbate, 17 ng/L, and fenpropidin, 23 ng/L), two antidepressants (amitriptyline, 304 ng/L, and paroxetine, 26 ng/L), and two anthelmintic agents (mebendazole, 65 ng/L, and albendazole, 48 ng/L) could be identified in the two toxic fractions. The artificial mixture of the identified six compounds could explain 79% of the observed effect, with albendazole and paroxetine as the predominant contributors (49% and 49%, respectively) affecting the sea urchin embryogenesis activity.

A study of spray deposit and its correlation with insect mortality was made during a pilot-control study using mexacarbate against the 4th-, and 5th-instars of Choristoneura occidentalis Freeman in northern Idaho. Spray formulation was applied by 2 airplanes (C-47) at the rate of 0.15 lb mexacarbate/U. S. gal/acre (68.0 g/3.785 1/0.40 hectare) to 2073 acres (840 hectares) of mountainous forest composed mainly of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, and grand fir, Abies grandis (Dougl.) Lindl. Measurements of deposit spray droplets showed that the volume median diam was 114 μm. Spray deposit varied considerably in the target area (inter-, and intra-tree variation) at the forest floor level, under the tree canopies, and in the forest openings. The mean spray deposit on the forest canopy was 2.62 μg of mexacarbate/75 needles. The mean spray deposit reaching the ground level under the trees was 0.046 gal/acre (0.426 l/hectare) and 8 drops/cm2, in adjacent small openings 0.084 gal/acre (0.782 l/hectare) and 16 drops/cm2, and along a block transect in an open-type situation 0.164 gal/acre (1.530 l/hectare) and 24 drops/cm2. Significantly higher deposit was found on the upwind than the downwind side of the trees. Larval mortality also was variable. The mean corrected spruce budworm mortality, 8 days after treatment, was 46% ranging from 0 to 100%. Using the means of grouped data, a high correlation (r = 0.95) was found between deposit in tree crowns and larval mortality. Deposit mortality regression showed that 2 and 16 μg of mexacarbate/75 needles were needed for obtaining LD50 and LD95, respectively. This relationship indicated that only 38% of the sample trees had enough mexacarbate for LD50 and 1% for LD95. Zusammenfassung Zur Verteilung der Spruhtropjchen von Mexacarbaten vom Flugzeug aus in einem Nadelwald und ihre Korrelation mit der Sterblichkeit von Choristoneura occidentalis Freeman Eine Untersuchung der Spruhtropfchenverteilung und deren Korrelation mit der Sterblichkeit der 4. und 5. Larvenstadien von Choristoneura occidentalis wurde unter Verwendung von Mexacarbate in Nord Idaho durchgefuhrt. Gespruht wurde mit Hilfe von zwei Flugzeugen (C-47) und einer Anwendungsmenge von 0,15 lb von Mexacarbate pro U.S. Gal pro acre (68,0 g pro 3,785 l pro 0,40 Hektar) fur 2,073 acres (840 Hektar) von vorwie-gend Douglasien, Pseudotsuga menziesii Mirb. (Franco) und Groser Kustentanne, Abies grandis (Dougl.) Lindl. Die Messungen der aufgespruhten Tropfchen zeigten, das diese einen mittleren Durchmesser von 114 μm hatten. Die Dichte des Spruhbelags differierte zwischen der Waldboden-oberflache unter dem Kronendach und in den Lichtungen bedeutend. Die mittlere Spruhmenge auf dem geschlossenen Kronendach betrug 2,62 μg Mexacarbate je 75 Nadeln. Der durchschnittliche Spruhbelag auf dem Waldboden erreichte unter den Baumen 0,046 Gal pro acre (0,426 l pro Hektar) und 8 Tropfchen pro cm2, in benachbarten kleinen Lichtungen 0,084 Gal pro acre (0,782 l pro Hektar) und 16 Tropfchen pro cm2 sowie entlang der Waldschneisen in einem sehr locker gestellten Bestand 0,164 Gal pro acre (1,530 l pro Hektar) und 24 Tropfchen pro cm2. Ein gesichert hoherer Belag auf der dem Wind zugekehrten Baumseite als auf der dem Wind abgekehrten Seite wurde ermittelt. Die Sterblichkeit der Larven war kleinortlich sehr unterschiedlich. Der berichtigte Durchschnitt der Sterblichkeit von Choristoneura occidentalis 8 Tage nach dem Spruhen betrug 46%; die Einzelwerte streuten von 0 bis 100%. Durch Verwendung der Durchschnitte von Gruppen von Einzelwerten wurde eine gute Korrelation (r = 0,95) zwischen der Belagsmenge in den Baumkronen und der Sterblichkeit der Larven nachgewiesen. Die Regressionslinie fur die Korrelation - Auftragsmenge - Sterblichkeit zeigte, das ein Belag von 2 und 16 μg Mexacarbate pro 75 Nadeln erforderlich war, um bei den Larven Sterblichkeitsquoten von 50% und 95% zu erreichen (LD50 und LD95). Es zeigte sich, das nur 38% der Probebaume genugend Mexacarbate zum Erreichen der 50% Larvensterblichkeit und nur 1% der Probebaume zum Erreichen der 95% Larvensterblichkeit erhielten.

Five spray mixes of mexacarbate (4-dimethylamino-3,5-xylyl N-methylcarbamate) were prepared using different inert ingredients. Among the mixes, ZE-DIL was oil-based, ZE-EML-1 14 and ZE-EML-3409 were emulsions, ZE-WP-W was a wettable powder in water, and ZE-FL-W was a flowable in water. The mixes were sprayed over potted balsam fir [Abies balsamea (L.) Mill.] seedlings in a laboratory chamber and foliar residues were analyzed by gas chromatography. The results showed that the ratios of the initial dislodgeable to penetrated residues were low for ZE-DIL, ZE-EML-114 and ZE-EML-3409, but were high for ZE-WP-W and ZE-FL-W. The latter two spray mixes contained mexacarbate in the particulate form, and contributed to greater surface residues than those of the former three spray mixes which contained mexacarbate in the solution or emulsion form. Foliar residues declined rapidly during 0 to 3 d post-spray, with half-lives (DT 50 ) ranging from 0.84 to 1.73 d. The rate of decline was slow from 3 to 20 d post-spray and the DT 50 values ranged from 2.49 to 4.65 d. Mexacarbate volatilized and codistilled appreciably within 24 h. Volatilization occurred more from dislodgeable residues than from penetrated ones, whereas codistillation occurred from both dislodgeable and penetrated residues. The penetrated residues of ZE-WP-W and ZE-FL-W volatilized less than those of ZE-DIL, ZE-EML-114 and ZE-EML-3409. This behaviour was due to the presence of mexacarbate in the particulate form in the former two spray mixes, as opposed to its presence as a solution or as an emulsion in the latter three spray mixes.

Mobility and metabolic fate of 14 C-mexacarbate (4-dimethlyamino-3,5-xylyl N-methylcarbamate) were studied using columns containing sandy and clay loam forest soils. Flooding and subsequent analysis of the soil segments showed the presence of free and bound (nonextractable) residues. The bulk of the 14 C-labelled material was adsorbed onto the litter layers. However, when the columns were saturated with 454 μg of the material, a small part of the radioactivity moved beyond the column length into the leachate. Analysis of the litter segments and the leachate showed carbamate moieties, phenols and other metabolites. Incubation of the soil columns under aerobic (dry) and anaerobic (wet) conditions for 30 d showed the retention of radioactivity in litter layers. The quantities of mexacarbate and its degradation products found were influenced, to some extent, by the soil type and incubation conditions. Except for phenolic and polar metabolites, no intact carbamate moieties were found in the litter after the 30-d incubation period. Mexacarbate seemed to breakdown rapidly in forest soil columns into various degradation products. A metabolic pathway for its degradation in soil is proposed.

The distribution and persistence of aerially applied mexacarbate were studied in a New Brunswick aquatic forest environment after spraying twice at a dosage of 70 g A.l./ha using a fixed‐wing aircraft. Average droplet density (drops/cm2) and ground deposition (g A.1./ha) between the two applications differed considerably. The values for the first and second applications were 1.7 and 0.73, and 5.2 and 2.0, respectively; but the average NMD (20 μm) and VMD (36 μm) for both applications were nearly the same. The maximum 1‐h postspray concentrations of mexacarbate in the stream and pond waters were 0.73 and 18.74 ppb, respectively. Concentrations fell rapidly to below detection limits within 12 h in stream and within 3 d in pond water. Cattails (Typha latifolia), manna grass (Glyceria borealis) and bog moss (Sphagnum sp.) collected from the pond contained peak 1‐h postspray concentrations of 720, 482 and 81 ppb, respectively. The concentration levels decreased rapidly and the average half‐lives of th...

A sensitive and selective high-performance liquid chromatographic method with post-column derivatization, using o-phthalaldehyde and 2-mercaptoethanol, is described for the analysis of aminocarb, mexacarbate and some of their carbamate metabolites. The separation system consisted of an RP-8 OS (10 μm) 20 cm × 4.6 mm I.D. column, an acetonitrile-water mobile system and a reactor for the hydrolysis of analytes from column effluents and fluorophore formation. The fluorophores were detected at 230 nm (excitation) and 418 nm (emission). The recoveries of the carbamates in spiked natural water at 2 and 20 ng/ml fortification levels ranged from 72.0 to 98.4% with relative standard deviations of 5.0 to 11.5%. The recoveries for spiked forest soil at 20 and 200 ng/g fortification levels ranged from 74.1 to 97.6% with relative standard deviations of 5.8 to 10.7%. Limits of detection and quantification for all the analytes were 0.1 and 0.4 ng in water and soil, respectively.

This study was conducted to determine if metabolites of mexacarbate contribute to its residual toxicity to spruce budworm (Choristoneura fumiferana) larvae. Potted white spruce (Picea glauca) trees were treated with ‘Zectran’ UCZF # 19 at 100 g a.i. ha−1 and kept in a glasshouse. Mexacarbate residues declined by 98–99% within three days and reached non-detectable levels 10 days after treatment. Mortality of larvae fed on buds from these trees declined more gradually and was still 19–27% when exposed 10 days after treatment. The very low levels of mexacarbate (

A pseudoplastic spray mixture was prepared from fenitrothion, polymeric adjuvants and humectants. Three Newtonian spray mixtures were prepared, one each from fenitrothion, aminocarb and mexacarbate respectively, using oils, surfactants and cosolvents. The spray mixtures were sprayed over potted seedlings of balsam fir using a spinning disc atomizer, at an application rate of 1.5 L/ha. Aminocarb and mexacarbate were each sprayed at 70 g active ingredient (AI)/ha, whereas fenitrothion, at 210 g AI/ha. Spray droplets were sampled with Kromekote® cards and deposits were collected on glass plates. Foliar droplets were counted and pesticide concentrations were measured by gas-liquid-chromatography. Physical properties measured were: viscosity-shear rate relationship, surface tension and volatility. The data indicated that the presence of the polymeric adjuvants imparted pseudoplastic behavior to the spray medium. Because of this, the mixture provided a markedly larger droplet size spectrum and much greater deposit concentrations of the insecticide both on conifer foliage and on the sampling units.

Laboratory dose-response studies were conducted with four species of adult bees, Apis mellifera (workers), Andrena erythronii (females), Megachile rotundata (females), and Bombus terricola (workers), using six insecticides, permethrin, mexacarbate, aminocarb, fenitrothion, carbaryl, and trichlorfon. All insecticides were applied topically to the thorax of the bees as technical grade in an acetone carrier. Mortality was accumulated over 48 h, and probit analyses were conducted separately on data sets expressed in units of μgAI (active ingredient)/g body weight and of μgAI/bee. LD50 values with 95% confidence limits and slopes with standard errors are provided for each bee/insecticide combination in each data set. Relative toxicities, relative susceptibilities, and fresh body weights are also provided. The analysis in units of μgAI/g body weight indicated that the insecticides were typically ranked in order of decreasing toxicity—permethrin, mexacarbate, aminocarb, fenitrothion, carbaryl, and trichlorfon. Likewise, the bees ranked from the most to least susceptible in the order of A. mellifera, A. erythronii, M. rotundata and B. terricola. Trends within the data set for units of μgAI/bee were less consistent. These data are discussed and compared with other published data on the toxicology of insecticides to bees and from the perspective of risk assessment.

This paper describes the application of high-flow (up to 2 mL/min) ion spray to the LC/MS determination of compounds of pharmaceutical and environmental interest with standard (HPLC) columns without established postcolumn splitting of the flow. It also illustrates the use of a nonvolatile mobilephase buffer, potassium phosphate, for the LC/MS determination of lysergic acid diethylamide (LSD). To achieve practicality and analytical ruggedness of the system, a liquid shield is placed between the sprayer and the ion sampling capillary, resulting in full-scan low-nanogram determination of quaternary ammonium drugs. The system also allows the use of gradients which is demonstrated for the analysis of carbamate pesticides and in particular for mexacarbate in pond water.

Zectran (4-dimethylamino-3,5-xylyl N-methyl-carbamate), a carbamate insecticide (active ingredient [AI] mexacarbate), was aerially applied to two 300 ha plots of coniferous forest at dosage rates of 70 and 140 g AI/ha, respectively. The brains of 288 birds collected from the treated areas and 84 birds from untreated areas were sagittally sectioned into approximately equal halves. Each of the laboratories participating in the study, the Forest Pest Management Institute (FPMI) and the Canadian Wildlife Service, Atlantic Region (CWS), assayed one half of each brain for cholinesterase (ChE) activity and the results were compared. The ChE estimates of the two laboratories on half brains from the same birds were poorly correlated (R = 0.136, P less than 0.05) and differed significantly (P less than 0.00005). The reasons for this are uncertain. Despite the discrepancy in ChE estimates, however, separate statistical analysis of each data set produced the same general conclusion: the ChE response to Zectran exposure was statistically significant but biologically unimportant. In both data sets, statistically significant ChE responses by niche and time since spraying were found. The dosage rate emitted from the airplane was a better predictor of ChE activity in the canopy niches than was volume deposited at ground level, but volume deposited was a more useful predictor for ground birds in most situations. These results are discussed in the context of a proposal to develop a reference file of normal brain ChE activities of common wildlife species.

Mexacarbate (4‐dimethylamino‐3,5‐xylyl N‐methylcarbamate) insecticide has potential for use in spruce budworm (Choristoneura fumiferana Clem.) control operations in Canada. Its persistence and fate in balsam fir (Abies balsamea (L.) Mill.), litter and soil samples were studied by spraying aerially oil‐based and water‐based formulations, each at 70 g A.I./ha over a coniferous forest near Bathurst, New Brunswick. The oil‐based formulation gave the maximum concentration of the chemical in the substrates studied. In fir needles, the highest concentrations observed were 0.51 ppm and 0.19 ppm (fresh weight) for the oil‐based and emulsion formulations respectively, 1 h after application. The residue levels decreased very rapidly with a half‐life of approximately 5 h. Three and eight days after the spray application of the emulsion and oil formulations respectively, the concentrations of mexacarbate in foliage decreased to trace levels ( 0.008 ppm). Only very low levels of residue were detected in litter...

Laboratory tests with selected carbamate, organophosphorus, and pyrethroid insecticides demonstrated that the pyrethroid permethrin has the best potential for controlling newly hatched larvae of Zeiraphera canadensis Mut. and Free. Permethrin possessed high crawling contact toxicity (toxicity of insecticide deposits on foliage when contacted by crawling larvae) and direct contact toxicity to first-instar larvae and exhibited long residual effectiveness on potted, white spruce trees. Chlorpyrifos, fenitrothion, mexacarbate, and methomyl had high crawling contact toxicity but short residual activity. Azinphos-methyl appeared to possess long residual effectiveness but relatively low crawling contact toxicity. Aminocarb and thiodicarb exhibited short residual effectiveness and relatively low toxicity. In field trials, an aerial application of permethrin (70 g/ha) at egg hatch resulted in an 81% population reduction and limited the destruction of tree leaders to 9%. Leader destruction was greater than 19% after treatments of permethrin at 35 g AI/ha or aminocarb at 180 g AI/ha or aminocarb twice at 90 g AI/ha. Leader destruction in an untreated plantation was 51%.

Laboratory studies on toxicity of three carbamate (mexacarbate, carbaryl, and aldicarb) and three organophosphorus (trichlorfon, formothion, and phorate) compounds were made on two species of snails, Lymnaea acuminata Lamarck and Pila globosa Swainson. L. acuminata was more sensitive to the pesticides tested. LC50 values computed for different exposure periods from 24 to 240 h showed a gradual decrease as the exposure time was increased. Although trichlorfon was most toxic to L. acuminata and mexacarbate to P. globosa , the relative LC50s of the six compounds varied at different exposure periods. A possible explanation on the basis of pharmacological evidences and structure-activity of these compounds has been given.

The nature of a reductive system which actively degrades mexacarbate in the rat intestine and liver was investigated. The system is characterized by its stability against heat and protease treatments and its requirements for a flavin cofactor and an acidic pH for a maximum activity. As a result of purification and spectroscopic identification attempts the system responsible for the above reductive activity was identified to be flavoprotein. Under anerobic conditions such flavoproteinflavin cofactor systems degrade mexacarbate first to 4-N-desmethylmexacarbate and then to polar water-soluble metabolites.

The toxicities of acephate, aminocarb, carbaryl, chlorpyrifos, chlorpyrifos-methyl, methomyl, mexacarbate, permethrin, and trichlorfon to last instar western spruce budworm, Choristoneura occidentalis Freeman, were significantly altered by the presence of host-plant foliage. The pyrethroid permethrin was significantly more toxic when sprayed directly on fully exposed larvae than when first sprayed on foliage. However, all other toxicants were more toxic sprayed on foliage. A toxicologically-based method was used to assess the residual toxicities of the nine chemicals. Each chemical was applied to potted seedlings at its respective LD90-foliage, then weathered for up to 7 days. Significant differences in toxicity were related to both insecticide and weathering interval. The toxicities of carbaryl and permethrin were least affected by weathering.

The degradation and metabolism of mexacarbate were studied in two types (sandy loam and clay loam) of sterile and nonsterile forest litters after incubation for 45 days under aerobic and submerged conditions. Degradation of the chemical in non‐autoclaved litters was rapid initially and reached a maximum after 30 d. The rate of formation of 14CO2 and the amount, the extractable metabolites produced and the nonextractable 14C adsorbed onto the litters varied depending on the litter type and experimental conditions. Rate constants and half‐lives (t1/2) of evolution of 14CO2 were very similar for the aerobic and submerged conditions. However, the t1/2 values for the clay loam litter were slightly higher than those for the sandy loam litter. Litter microbes played a major role in the degradation of mexacarbate and formation of 14CO2. Metabolites detected included demethylated carbamates, various xylenols, polar and other unknown products. The principal degradative pathway for the chemical appears to b...

The contact toxlaty of 100 insecticides to last stage larvae of Choristoneura occidentalis Freeman was tested by topical application in a 10-yr series of screening experiments. Pyrethroids were generally the most toxic group of chemicals tested. Compounds more toxic than the standard, mexacarbate, at LD90 were: bioethanomethrin, (+) cis -resmethrin, (+) trans -resmethrin, (+) cis -phenothrin. ENT 29117 (5-benzyl-3-furylmethyl (IR,3S,E) 2,2-dimethyl-3-(2-oxo-3-tetrahydrothiophenylidenmethyl) cyclopropanecarboxylate), resmethrin, and NRDC 143 (3-phenoxybenzyl (±)-3-(2,2-dichlorovinyl-2,2-dimethylcyclo-propanecarboxylate). Mexacarbate spray was tested on the western spruce budworm at selected developmental stages. First instars were least susceptible at both LD50 and LD90; instars 3–5 and 6th instars weighing less than 110 mg were most susceptible. Since long-term laboratory realing of insects did not change their responses to 3 representative chemicals periodically tested during this series of experiments, the results represented a valid estimate of relative toxicity.

Treatment of goldfish with β-naphthoflavone (ip) resulted in induction of hepatic monooxygenase activity in a dose-dependent manner. Levels of 7-ethoxyresorufin- O -deethylase and mexacarbate NADPH-dependent oxidative metabolism as well as cytochrome(s) P -450 were increased. Other substrates which have been associated with 3-methylcholanthrene (3-MC)-type induction in mammals were unchanged as was δ-aminolevulinic acid synthetase. Enzyme activities were inhibited by carbon monoxide and piperonyl butoxide confirming their cytochrome P -450 nature. NADH was found to stimulate metabolism in a significant manner with NADPH. pH-dependent ethyl isocyanide binding characteristics were similar in control and induced preparations while mexacarbate binding to oxidized microsomes revealed a higher apparent affinity constant ( K s app ) as well as greater overall binding in induced preparations. SDS-gel electrophoresis revealed an increased band with a molecular weight of approximately 56,000.

Mexacarbate (Zectran®) is a carbamate insecticide that has been considered for controlling forest insect pests, particularly in northern conifer forests. The effects of different water characteristics (temperature, hardness, and pH) and aging (deactivation) on its toxicity to coho salmon(Oncorhynchus kisutch), Atlantic salmon(Salmo solar), brown trout(Salmo trutta), fathead minnows(Pimephales promelas), bluegills(Lepomis macrochirus), and yellow perch(Perca flavescens), were determined. Identification and toxicity of the breakdown products were also investigated. Mexacarbate was less toxic to eggs than to other life stages of fish. Water temperature and hardness did not affect its biological activity, but pH did—the insecticide was was 38 times more lethal to bluegills at pH 9.5 than at pH 6.5. Solutions of mexacarbate hydrolyzed to more toxic breakdown products during the first 3 weeks of aging; the rate of hydrolysis increased as alkalinity increased. The breakdown product 4-amino-3,5-xylenol was 70 times more lethal to bluegills than mexacarbate in 96-hr bioassay tests at pH 7.5. However, this breakdown product was apparently not present in sufficient concentrations or long enough to cause fish mortality when the insecticide is applied at rates recommended for control of forest insects.

Continuous-flow laboratory bioassays were used to assess the acute toxicities of four formulated insecticides to representative stream invertebrates. Toxicities (48-h LC50) ranged from 3.2 to 7.4 μg/L for permethrin, from 39 to 269 μg/L for fenitrothion, from 478 to 2863 μg/L for aminocarb, and from 99 to 492 μg/L for mexacarbate. Slopes of the probit lines were similar for acetylcholinesterase inhibitors (fenitrothion, aminocarb, and mexacarbate), but slightly lower for permethrin. All test species responded to all of the insecticides at concentrations of 0.25 μg/L for permethrin, 10 μg/L for fenithrothion, and 25 μg/L for aminocarb and mexacarbate by drifting in the test chambers.

Field bioassays were used to assess the toxicities of four formulated insecticides to representative stream invertebrates. Toxicities (48-h LC50) after a 1-h application period ranged from 2.0 to 7.1 μg/L for permethrin, 82 to 284 μg/L for fenitrothion, 344 to 1276 μg/L for aminocarb, and 251 to 1504 μg/L for mexacarbate. Invertebrates drifted at concentrations of permethrin greater than 0.5 μg/L, and at concentrations of fenitrothion, aminocarb, and mexacarbate greater than 10 μg/L. An aerial application of 280 g AI/ha fenitrothion with no stream buffer was made to compare bioassay results with impact to aquatic invertebrates under operational spray programs. Concentrations of fenitrothion peaked 30 min after spray at 31.0 μg/L and declined to less than 1.0 μg/L within 14 h. Numbers of drifting invertebrates increased 20-fold 3 h after spray and declined to before-spray numbers within 24 h. Mortalities of caged invertebrates in the stream ranged from 0% for Pycnopsyche sp. to 16% for Simulium venustum (Say). The field bioassay accurately predicted the impacts of fenitrothion on stream invertebrates in this situation.

Field samples of freshwater algae were examined to determine the effect of the insecticide Zectran on photosynthesis rate. Concentrations of Zectran between 10 and 10(3) parts per billion (ppb) affected neither O2 production nor NaH14CO3 uptake in any of the seven genera tested. However, Zectran at a concentration of 10(4) ppb after 1 hour effected a reduction in photosynthesis of Chroococcus, Oedogonium and in a mixed sample composed of Zygnema,Mougeotia and Spirogyra. Mougeotia, Spirogyra and Schizogonium were not affected by exposure to 10(4) ppb Zectran after 1 hour, but O2 production was significantly reduced after 24 hours of exposure to this same concentration.

A rapid and sensitive analytical technique to quantify carbamate insecticides at nanogram levels is reported using resin column and sorption, and desorption followed by N-P gas-liquid chromatography (GLC) analysis. The carbamates were extracted from natural water by percolation through a column of Amberlite XAD-2, followed by elution with ethyl acetate. The carbamate residues were directly analyzed by GLC with a Tracor Model 702 N-P detector. The recoveries for several carbamates including aminocarb, mexacarbate, carbaryl, propoxur, carbofuran, pirimicarb and methiocarb were from 86 to 108% at 1.0 and 0.01 ppm levels. Only 41 to 58% was recovered for methomyl. The extraction efficiency of Amberlite XAD-2 was pH-dependent as indicated in the extraction of aminocarb. More than 90% of the added aminocarb was recovered from phosphate buffer by the described method at pH 5.0 to 7.5 at 5.0 and 0.5 ppm levels.

k2, Kd and ki, for 2 organophosphorus (Phorate and Formothion) and 2 carbamate pesticides (Mexacarbate and Carbaryl) using acetylcholinesterase present in homogenates of the nervous tissue of the snail Lymnaea acuminata, were determined. Calculation of zero time velocities demonstrated that even in their P-S form the organophosphate compounds inhibited snail acetylcholinesterase. The kinetic constants of the 2 carbamates have been explained on the basis of their structure. The toxicity of the 4 pesticides has been explained on the basis of their kinetic constants.

A simple, sensitive and reliable analytical method has been developed and reported for mexacarbate (4-ditnethylamino-3,5-xylyl N-methylcarbamate) and five of its possible degradation products likely to be found in environmental samples using reversed-phase high-performance liquid chromatography with isocratic and gradient solvent systems. All chromatogram peaks were Identified through comparison to standards. The method has been used to identify and separate the six compounds from a mixture of the standards. It has been evaluated under different column conditions and with different mobile phases. Best resolution of the analytes was obtained by using a gradient solvent system consisting of CH3CN and H3O detecting at 200 nm and 30°C using a HP-RP8, 10 μ m, 20 cm 4.6 mm column.

The synergistic effects of piperonyl butoxide (PB)2, sulfoxide (SU), and dimethyl amino aniline (DAA) used in conjunction with two organophosphate pesticides (phorate and formothion) and two carbamate pesticides (mexacarbate and carbaryl) were examined in terms of the LC50 and acetylcholinesterase (AChE) inhibition in the snailLymnaea acuminata. The three synergists reduced the LC50 of phorate, formothion, mexacarbate, and carbaryl at exposure periods ranging from 24 to 144 hr. PB and SU had strong synergistic action; DAA had little effect; the highest synergistic ratio (70) was found with carbaryl and PB. The synergists enhanced thein vitro inhibition of cholinesterase caused by the pesticides; the synergistic effect onin vitro inhibition, however, was lower, compared to the change in the LC50.

The influence of viscosity, density, surface tension, volatility and apparent viscosity-shear rate relationship on droplet-size spectra and deposit characteristics of two mexacarbate (4-dimethylamino-3,5-xylyl methylcarbamate) formulations, one oil-based and one water-based, was studied following spray application under laboratory and field conditions. The oilbased formulation had a higher viscosity, a higher apparent viscosity at high shear rates and a lower volatility than the water-based formulation; application through rotary atomisers gave larger droplet sizes, more droplets cm−2 and deposits of the active ingredient ha−1 than those from the water-based formulation in both the laboratory and field studies. Both formulations had similar surface tensions and densities and, therefore, the contribution of these properties to droplet-size spectra could not be determined. Among the three properties (viscosity, apparent viscosity-shear rate relationship and volatility), volatility contributed most to the deposit patterns of the two formulations.

A simple method was developed to quantify a fluorescent dye tracer [Erio Acid Red (EAR)] in spray deposits of forestry insecticides on balsam fir foliage. Three types of instruments, Beckman DU‐7 Spectrophotometer, Beckman Model 772 Ratio Fluorometer, Turner Model 111 Fluorometer, were investigated for sensitivity and precision during quantification of EAR in aqueous tank‐mix formulations of fenitrothion, ami‐nocarb and mexacarbate. Turner Fluorometer was found to be the most suitable out of the instruments tested, and the minimum detection limit was 0.5 ng/mL. Foliage samples were spiked with variable concentrations of EAR, extracted at different intervals of time after treatment, and cleaned using an Al2O3 column to remove plant pigments. EAR concentrations were quantified using Turner Fluorometer. Recovery was the greatest when extracted 12 to 15 min after spiking, but decreased rapidly as the time lapse between treatment and extraction increased. The minimum quantification limit (MQL) was 10 ...

Mexacarbate was less toxic to juvenile Atlantic salmon ( Salmo salar ) than its formulation, UCZF-19 (96-h LC50 - 19.5 and 3.4 mg/L, respectively). The increased lethality of the formulation is due to its volatile components (largely C3–C5 alkylbenzenes and naphthalene). The hazard indices of mexacarbate and UCZF-19 in forest spraying indicate low risk of direct mortality of juvenile Atlantic salmon.

Mortality of last instar western spruce bud worm, Choristoneura occidentalis Freeman, exposed to a series of increasing doses (topical application) or concentrations (diet incorporation) of 10 insecticides was analyzed over 7 d by time-dose-mortality regression. Regression based on the complementary log-log model was useful for analyzing time trends for all dose levels simultaneously. Each of the 10 insecticides acted more quickly when applied topically. In both kinds of experiments, speed of lethal action of the insecticides depended on dose or concentration. The statistical methods developed to estimate lethal doses as functions of time and median times of death as functions of dose are more efficient than methods published previously.

The present study was undertaken to explore the acute toxicity of three carbamate pesticides, aldicarb, carbaryl, and mexacarbate, on a population of Paramecium multimicronucleatum. The toxicity was evaluated by the Warburg respirometer and the static acute plate assay. Aldicarb, carbaryl, and mexacarbate were shown to significantly inhibit cumulative oxygen uptake at 24 hr in the paramecium culture at 160, 120, and 100 ppm, respectively. Aldicarb, carbaryl, and mexacarbate concentrations of 60, 20, and 10 ppm demonstrated no inhibition of cumulative oxygen uptake when compared to a paramecium control at 24 hr. Pesticide concentrations intermediate to the high and low concentrations demonstrated varying degrees of inhibition. Static plate assay data for aldicarb demonstrated LC50 values of 93, 104, 122, and 145 ppm at 24, 17, 13, and 9 hr, while carbaryl demonstrated LC50 values of 28, 34, 46, 65, and 105 ppm at 24, 17, 13, 9, and 7 hr, respectively. Mexacarbate LC50 values were 19, 25, 35, 57, and 83 ppm at 24, 17, 13, 9, and 7 hr. Oxygen uptake values compared favorably with the static assay data. Scanning electron micrographs demonstrated several morphologic changes in paramecium with increased pesticide concentration and exposure time including ciliary abnormalities and disruption of surface structure.

Volatilization of three forestry insecticides, aminocarb, fenitrothion and mexacarbate, from balsam fir seedlings was investigated after spray application of these chemicals as aqueous emulsions in a laboratory chamber at a dosage rate of 210 g (active ingredient)/ha. Highest airborne residues were found in the spray chamber at 0.25 h after mexacarbate application (21.7 μg/L) and lowest after aminocarb (6.3 μg/L). The treated seedlings were transferred to air‐tight chambers for investigation of volatilization over a 12 h post‐spray period. Mexacarbate was the most volatile, while aminocarb was the least. From the initial amounts of deposits on the seedlings, about 30% of mexacarbate, 15% of fenitrothion and 9% of aminocarb were lost within 12 h by volatilization. Residue levels that remained in the seedlings at 12 h post‐spray were ca. 70% of the initial values for aminocarb and fenitrothion, but were only ca. 9% for mexacarbate. Calculations on the mass‐balance indicated that 60% of the deposite...

The direct toxicity of 5 common acaricides toAmblyseius brazilli El-Banhawy was tested. Omethoate proved to be the most toxic and Chlorobenzilate the least toxic. LC50 were 1.2ppm, 220ppm, 720ppm and 1250ppm for Omethoate, Mexacarbate, Dicofol, Mitran and Chlorobenzilate respectively. The indirect toxicity was also studied by providing the female predators with the phytophagous miteAponicus spinosus (Banks) previously treated by Chlorobenzilate and Mexacarbate. The females were fed on the treated as well as the untreated prey. The eg laying was interrupted and almost stopped in the case of Mexacarbate.

The snailLymnaea acuminata, vector of the liver flukesFasciola hepatica andFasciola gigantica, was exposed to 40% and 80% LC50 doses of the pesticides 12/24 mg/L phorate (O,O-diethylS-(ethylthio) methyl phosphorodithioate) and 2.5/5.0 mg/L of mexacarbate (4-dimethylamino)-3,5-dimethylphenyl methyl carbamate) for 24 or 48 hr. These pesticides, although considered to be antiacetylcholinesterase agents, inhibited alkaline phosphatase and enhanced the activity of acid phosphatase in hepatopancreas, mantle, intestine, and foot of the snail. Trypsin activity in the alimentary canal of the snail was also inhibited. Discontinuation of pesticide treatment resulted in partial recovery in mexacarbate-treated animals while in phorate-treated animals the effect of the pesticide was largely irreversible.