Efficacy of Spring and Fall Treatments of Carbaryl for Protecting Ponderosa Pine From Mortality Attributed to Mountain Pine Beetle (Coleoptera: Curculionidae).

High-value trees, such as those growing in residential, recreational, or administrative sites, are often susceptible to colonization by bark beetles (Coleoptera: Curculionidae: Scolytinae) as a result of increased amounts of stress associated with off-site plantings, drought, soil compaction, and/or mechanical injury. The value of these trees, cost of removing dead trees, and loss of aesthetics often justify the use of insecticides to protect trees from mortality attributed to bark beetles. Carbaryl (1-naphthyl methylcarbamate) is among the most effective, economically-viable, and ecologically-compatible insecticides available for protecting conifers from several species of bark beetles in the western United States. Treatments are usually applied in spring prior to initiation of flight of the target species. We evaluated the efficacy of spring and fall applications of carbaryl for protecting individual ponderosa pine, Pinus ponderosa Dougl. ex Laws. (Pinales: Pinaceae), from mortality attributed to mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), in Idaho. Both spring and fall treatments of 2.0% a.i. carbaryl (maximum label rate; Sevin SL, Bayer Environmental Science, Montvale, NJ 07645) provided one field season of protection, and thus should be applied annually if tree protection is desired for multiple years. Our research also provides some insight on the efficacy of carbaryl treatments after wildfire. We found no evidence that a mixed-severity wildfire negatively affected the efficacy of carbaryl treatments.

Efinaconazole 10% nail solution: a new topical treatment with broad antifungal activity for onychomycosis monotherapy.

BACKGROUND: Topical therapies for onychomycosis are associated with less adverse events than systemic therapies, but poor nail penetration limits their efficacy. Consequently, an efinaconazole 10% nail solution was developed. OBJECTIVE: To review the evidence supporting the usefulness of efinaconazole monotherapy in onychomycosis management. METHODS: PubMed and clinicaltrials.gov databases and abstracts from the 2013 annual meeting of the American Academy of Dermatology were searched in April 2013 using the terms "efinaconazole," "IDP-108," and "KP-103." RESULTS: In vitro, efinaconazole possesses a broad antifungal activity similar or superior to that of other antifungals. Its low affinity for keratin results in good nail penetration. Efinaconazole 10% nail solution administered daily for 36 or 48 weeks to treat mild to moderate toenail onychomycosis caused by dermatophytes results in complete and mycologic cure rates of 15 to 25% and 53 to 87%, respectively. No serious skin reaction is associated with its use. CONCLUSION: Efinaconazole 10% nail solution is a promising new treatment for onychomycosis.

Carbaryl-induced histopathologic alterations in the digestive tract of the Levantine frog, Pelophylax bedriagae (Anura: Ranidae).

In this study, histopathologic changes following carbaryl exposure for 96 hr were investigated in the digestive tract of Levantine frog, Pelophylax bedriagae. Adult frogs were exposed to carbaryl once by oral gavage in concentrations of 0.05, 0.1, and 0.2 mg/g. Histopathological changes were more prominent in medium- (0.1 mg/g) and high-dose (0.2 mg/g) groups than in the low-dose (0.05 mg/g) group. Esophageal cells showed vacuolization, cellular swelling, nuclear pyknosis, karyolysis, and necrosis. Additionally, esophageal glandular atrophy and infiltration of inflammatory cells around esophageal glands were observed at medium and high doses. In the stomach, there were prominent histopathologic defects such as cellular swelling and necrosis in gastric glands, necrotic cells within the interstitial spaces, separation of epithelial cell layer, congested vessels, and hemorrhage at medium and high doses. In the intestine, detachment of epithelial layer, epithelial cell disorganization, inflammation, and necrosis were detected at medium and high doses. The results of this study showed that carbaryl caused adverse effects on the digestive tract of the Levantine frog, P. bedriagae.

Evidence for links between feeding inhibition, population characteristics, and sensitivity to acute toxicity for Daphnia magna.

A population experiment with Daphnia magna tested the hypothesis that short-term feeding inhibition provokes a shift in population structure that will vary with conspecific pressure (e.g., pressure occurring from individuals of the same species due to competition for food and space) and increases population sensitivity to a xenobiotic exposure due to size-dependent toxicity (e.g., decreasing sensitivity with increasing body length). Populations were exposed for one week to a feeding inhibitor (imidacloprid, 0.15 or 12.0 mg/L) followed by one week of recovery and one day of exposure to an acute toxin (carbaryl, 0.0098 mg/L). Identical exposure under low and high conspecific pressure was studied by delaying the start of exposure for half of the populations by two weeks; thus populations were in a different stage of population development when exposure occurred. Feeding inhibition of 97% (12.0 mg/L imidacloprid) caused a shift in population structure toward smaller individuals but also reduced population abundance by up to 56 ± 7% with a strong influence of conspecific pressure. Increased population sensitivity to carbaryl was observed after feeding inhibition of 97% as hypothesized. Carbaryl exposure for one day resulted in population decline of up to 23 ± 6% when populations were not previously exposed to imidacloprid. Identical carbaryl exposure provoked a four times stronger decline in population abundance when exposure occurred following feeding inhibition of 97%. In conflict with the hypothesis, this was at least in part due to changes in the reproductive strategy of daphnids following exposure to imidacloprid rather than driven by the shift in population structure. The differences in population sensitivity to additional stress (carbaryl) occurring one week after feeding inhibition caused by exposure to imidacloprid adds a further challenge to understanding potential impacts from multiple stressors as occurring in the field at the population level.

In vitro induction/inhibition of germinal vesicle breakdown (GVBD) in frog (Euphlyctis cyanophlyctis) oocytes by endocrine active compounds.

Oocyte maturation is transformation of oocytes into a fertilizable egg. This study examined the effects of four classes of chemicals: 1) acephate (organophosphate); 2) atrazine (herbicide); 3) cypermethrin and fenvalerate (synthetic pyrethroids); and 4) carbaryl (carbamate) on in vitro germinal vesicle breakdown (GVBD) of Euphlyctis cyanophlyctis oocytes. Follicles were isolated and defolliculated from surgically removed ovaries of E. cyanophlyctis and exposed to either progesterone (1 µM/mL) or graded concentrations (1, 5, 10, 15, and 20 µg/mL) of test chemicals. GVBD was evident by the presence of a white spot in the animal pole as well as the absence of germinal vesicles in sectioned heat-fixed oocytes. Percent GVBD was scored every 4 hours until 24 hours. Progesterone induced 77-84% GVBD, compared to 29-33% in controls, at 24 hours. Acephate induced 46-67% GVBD, whereas atrazine elicited 58-77% of GVBD. In cypermethrin or carbaryl- or fenvalerate-exposed oocytes, GVBD was limited to 22-28, 17-29 and 18-24%, respectively. The study infers that some chemical contaminants in the aquatic system may interfere with GVBD in amphibians. Because oocyte maturation is a prerequisite for the production of fertilizable eggs, any alteration in this process potentially impairs the fecundity of females.

Evaluation of cucurbitacin-based gustatory stimulant to facilitate cucumber beetle (Coleoptera: Chrysomelidae) management with foliar insecticides in melons.

The bitter plant-derived compounds cucurbitacins are known to stimulate feeding of adult cucumber beetles (Coleoptera: Chrysomelidae). A cucurbitacin-based gustatory stimulant applied as a flowable bait combined with either spinosad or carbaryl was compared with foliar sprays of spinosad and carbaryl for controlling two cucumber beetle species (Diabrotica undecimpunctata undecimpunctata Mannerheim and Acalymma trivittatum Mannerheim) in honeydew melons (Cucumis melo L.). Field studies were conducted on the University of California-Davis plant pathology farm in 2008 and 2009. Beetle densities after applications and fruit damage from beetle feeding were compared among treatments. In addition, beetle survival was compared within field cages placed over the treated foliage infested with beetles. Using all three measures of efficacy, we determined that the addition of cucurbitacin bait had no effect on the level of cucumber beetle control with carbaryl in either 2008 or 2009. In both years, spinosad did not significantly reduce cucumber beetle densities in either field cages or field plots and did not reduce fruit damage relative to the untreated control. The addition of the bait to spinosad did not improve its efficacy. A laboratory bioassay of the spinosad formulation used in the field showed it had significant lethal effects on adults of both cucumber beetle species. Results indicated that the bait formulation used did not improve cucumber beetle control but may benefit from the addition of floral attractants or using a different type of cucurbitacin.

Assessment of acetylcholinesterase activity in Clarias gariepinus as a biomarker of organophosphate and carbamate exposure.

The objective of this study was to investigate the response of acetylcholinesterase (AChE) activities in Clarias gariepinus in response to Organophosphates (Ops) and carbamate exposure. The AChE activities were determined in plasma, and eye and brain homogenates of unexposed and exposed fish using Ellman's method and 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) chromophore. The baseline AChE activities in plasma, eyes and brain tissues in unexposed fish were comparable between males and females (P > 0.05). Concentrations of pesticides that inhibited 50% (IC(50)) of AChE activities in brain homogenates following in vitro exposures were 0.003, 0.03, 0.15, 190, 0.2, 0.003 and 0.002 microM for carbaryl, chlorfenvinphos, diazinon, dimethoate, fenitrothion, pirimiphosmethyl and profenofos, respectively. The in vivo dose-effect relationships were assessed using chlorfenvinphos and carbaryl at different concentrations that ranged from 0.0003 to 0.06 microM and 0.0005 to 0.05 microM, respectively. Acetylcholinesterase activities were comparable in plasma, and eye and brain homogenates from control and carbaryl-exposed fish. Following exposure of fish to chlorfenvinphos at concentrations above 0.03 microM, a significant inhibition of AChE activities in plasma (84%) and eye homogenate (50%) was observed. The AChE activities in brain homogenate were comparable between chlorfenvinphos-exposed fish and controls. Because carbaryl cause reversible inhibition of AChE activities was found to be more potent than chlorfenvinphos that cause irreversible inhibition following in vitro exposure. Contrary, carbaryl was less potent than chlorfenvinphos after in vivo exposure possibly due to more rapid biotransformation of carbaryl than chlorfenvinphos. Findings from this study have demonstrated that inhibition of AChE activity in C. gariepinus is a useful biomarker in assessing aquatic environment contaminated by anticholinesterases.

Assessment of the toxicological interaction of sertraline with cholinesterase inhibiting insecticides in aquatic insects using the black fly, Simulium vittatum IS-7.

Sertraline is a selective serotonin reuptake inhibitor (SSRI) prescribed as an antidepressant. Although SSRIs are known to block serotonin reuptake sites on cell membranes, they also have been shown to inhibit acetylcholinesterase (AChE) activity. Thus, the interaction of these chemicals with other AChE inhibitors, namely, organophosphate and carbamate insecticides, is of interest. In addition, these insecticides have been shown to interact with serotonergic neuronal pathways creating questions as to how these chemicals might interact. In this study, the interactive effect of sertraline (SSRI) in binary combinations with carbaryl (carbamate insecticide) and diazinon (organophosphate insecticide) was assessed using a 48-h acute toxicity test with black fly larvae, Simulium vittatum IS-7. Results showed that observed mortality was bracketed by the independent action model and concentration addition model with the independent action model slightly underestimating mortality and the concentration addition model slightly overestimating mortality. Varying the concentration of the chemicals in the mixture did not indicate that sertraline was interacting with the insecticides to make them more toxic or vice versa. These results indicate that sertraline and the insecticides are likely eliciting toxicity at separate neuronal pathways since no interaction was observed.

Golfer exposure to chlorpyrifos and carbaryl following application to turfgrass.

Exposure of golfers to pesticides following their application to turfgrass is of concern to regulators, turfgrass professionals, and consumers. Multipathway exposures were evaluated for golfers on turfgrass treated with chlorpyrifos and carbaryl. Air concentrations and transferable foliar residues (TFRs) were measured to assess potential respiratory and dermal exposures, respectively. At the same time, exposure to individuals simulating the play of golf was determined by dosimetry and urinary biomonitoring. Individual golfer exposure was determined in 76 rounds of golf following eight applications of chlorpyrifos and two applications of carbaryl. Estimated exposures to golfers following full course and full rate applications of chlorpyrifos and carbaryl were 19-68 times below current U.S. EPA acute reference dose (Rfd) values, indicating safe exposures under U.S. EPA hazard quotient criteria. Dermal exposure was determined to be the dominant exposure pathway to golfers, accounting for approximately 60% of the chlorpyrifos absorbed dose and 100% of the carbaryl absorbed dose. This study also provides a set of transfer factors (TFs) that may be used to determine dermal exposure of golfers to pesticides using transferable residue data.

Assessment of absorbed doses of carbaryl and associated health risks in a group of horticultural greenhouse workers.

OBJECTIVE: This study was undertaken to estimate the absorbed doses of carbaryl and the associated health risks in a group of horticultural greenhouse workers in the Province of Quebec, Canada, using a toxicokinetic modeling approach. METHODS: A mathematical model was developed to relate the absorbed dose of carbaryl, the evolution of its body burden and that of its metabolites and the urinary excretion rate of biomarkers. The free parameters of this model were determined using published time course data in volunteers exposed to carbaryl under controlled conditions. The model was used to determine cumulative urinary amounts of 1-naphthol that would be excreted by a typical worker exposed to a pre-established no-observed-adverse-effect level (NOAEL) dose; this biomarker amount was then taken as a biological reference value below which the risks of health effects were considered negligible. As a measure of the applicability of this approach to practical situations, the model was used to estimate the dose of carbaryl absorbed by each greenhouse worker, starting from his/her cumulative urinary excretion time courses of 1-naphthol over a 24-h period following the onset of a work exposure. Their cumulative 1-naphthol levels were then compared to the biological reference value obtained from the model and the NOAEL dose. RESULTS: Following the onset of a work exposure to carbaryl, a clear increase in the urinary excretion rate of 1-naphthol was observed in most workers. The reconstructed absorbed doses were found to vary between 3.3 and 143 nmol/kg of body weight (bw) depending on the working conditions. Simulations of the observed cumulative urinary excretion time course of each worker also showed that exposure appeared to occur mainly (a) through inhalation for the applicators and individuals without direct contact with treated plants and (b) through the dermal route for individuals manipulating treated plants. Although the workers under study clearly appeared to have been exposed to carbaryl in the greenhouses, 24-h cumulative 1-naphthol levels ranged from 4.8 to 65.1% of the proposed biological reference value of 32 nmol/kg bw in 24-h urine collections following the onset of a work exposure. CONCLUSION: This suggests that the workers under study probably did not incur a serious health risk under the normal exposure conditions prevailing during the study period.

Simulating toxicity of carbaryl to Gammarus pulex after sequential pulsed exposure.

Aquatic nontarget organisms are typically exposed to sequential pulses of contaminants with fluctuating concentrations. We use the semimechanistic threshold damage model (TDM) to simulate survival of the aquatic invertebrate Gammarus pulex after sequential pulsed exposure to carbaryl and compare itto a simpler model based on time-weighted averages (TWA). The TDM is a process-based model and we demonstrate how to parametrize it with data from an uptake and elimination experimenttogether with data from a survival experiment with sequential pulses. The performance of the two models is compared by the fit to the first survival experiment and the simulation of another, independent survival experiment with different exposure patterns. Measured internal concentrations in the first survival experiment are used to evaluate the toxicokinetic submodel of the TDM. The TDM outperforms the TWA model, facilitates understanding of the underlying ecotoxicological processes, permits calculation of recovery times (3, 15, and 25 days for pentachlorophenol, carbaryl and chlorpyrifos respectively) and enables us to predict the effects of long-term exposure patterns with sequential pulses or fluctuating concentrations. We compare the parameters of the TDM for carbaryl, pentachlorophenol and chlorpyrifos and discuss implications for ecotoxicology and risk assessment.

Modeling combined effects of pulsed exposure to carbaryl and chlorpyrifos on Gammarus pulex.

Aquatic risk assessment can be improved if we are able to quantitatively predict the effects resulting from sequential pulsed exposure to multiple compounds. We evaluate two modeling approaches, both extended to suit multiple compounds, the semi-mechanistic threshold damage model (TDM), and a model based on time-weighted averages (TWA). The TDM predicts that recovery of damage to Gammarus pulex from exposure to chlorpyrifos takes longer than that from exposure to carbaryl and consequently that the sequence of exposure matters. We measured survival of the freshwater invertebrate Gammarus pulex after sequential pulsed exposure to carbaryl and chlorpyrifos. Two groups of organisms were exposed to a first pulse of either carbaryl or chlorpyrifos for 1 day and then, after a recovery period of two weeks, to a second pulse with the other compound. The comparison of mortalities caused by each pulse, as well as combined mortalities in both treatments, show that the sequence of exposure to pulses of contaminants does indeed matter. Previous exposure to chlorpyrifos leads to significantly increased mortality from subsequent pulses of carbaryl, but not the other way round. The TDM facilitates a process-based ecotoxicological explanation by simulating the recovery dynamics and outperforms the TWA model.

Differential sensitivity to anticholinesterase insecticides in the juvenile rat: effects on thermoregulation.

Organophosphate (OP) and carbamate (CB) insecticides inhibit cholinesterase (ChE) activity and induce acute hypothermia in adult rats. Studies showed that juveniles are generally more susceptible to neurotoxic insult than adults. However, little is known concerning the effects of OP and CB pesticides on thermoregulation in developing animals. Thus, alterations in core body temperature (Tc) in juvenile animals exposed to an OP and CB insecticide were investigated. Male rat pups were anesthetized on postnatal day (PND) 15 with metofane and a radio transmitter (Data Sciences) was implanted in the abdominal cavity to monitor Tc and motor activity (MA). Two days were allowed for recovery. The PND 17 pups were then dosed by oral gavage with the OP chlorpyrifos (CHP) (1, 5, 10, or 15 mg/kg) or the CB carbaryl (CAR) (10, 20, 80, 120, or 160 mg/kg) or the corn oil vehicle. Pups were returned to their dams and littermates immediately after dosing and monitored for the next several days. CHP doses of 10 and 15 mg/kg resulted in 1.0 degrees C and 2.4 degrees C reductions in Tc, respectively. Tc recovered to control levels by approximately 16 h after dosing. There was significant mortality in rats dosed with 15 mg/kg CHP (6 of 11). CAR doses of 10 to 80 mg/kg had little effect on Tc. The highest dose of CAR (160 mg/kg) resulted in a 1.3 degrees C reduction in Tc that recovered in 9 h. In contrast, past studies found that adult male rats become hypothermic at CHP doses of >25 mg/kg, whereas a CAR dose of 50 mg/kg is effective at inducing hypothermia. Overall, it appears that during the development from preweanling to adult rat, there is a progressive attenuation in CHP-induced hypothermia. Conversely, CAR-induced hypothermia increases as a function of development.

Thermoregulatory response to an organophosphate and carbamate insecticide mixture: testing the assumption of dose-additivity.

Most toxicity data are based on studies using single compounds. This study assessed if there is an interaction between mixtures of the anticholinesterase insecticides chlorpyrifos (CHP) and carbaryl (CAR) using hypothermia and cholinesterase (ChE) inhibition as toxicological endpoints. Core temperature (T(c)) was continuously monitored by radiotelemetry in adult Long-Evans rats administered CHP at doses ranging from 0 to 50mg/kg and CAR doses of 0-150 mg/kg. The temperature index (TI), an integration of the change in T(c) over a 12h period, was quantified. Effects of mixtures of CHP and CAR in 2:1 and 1:1 ratios on the TI were examined and the data analyzed using a statistical model designed to assess significant departures from additivity for chemical mixtures. CHP and CAR elicited a marked hypothermia and dose-related decrease in the TI. The TI response to a 2:1 ratio of CHP:CAR was significantly less than that predicted by additivity. The TI response to a 1:1 ratio of CHP and CAR was not significantly different from the predicted additivity. Plasma and brain ChE activity were measured 4h after dosing with CHP, CAR, and mixtures in separate groups of rats. There was a dose-additive interaction for the inhibition of brain ChE for the 2:1 ratio, but an antagonistic effect for the 1:1 ratio. The 2:1 and 1:1 mixtures had an antagonistic interaction on plasma ChE. Overall, the departures from additivity for the physiological (i.e., temperature) and biochemical (i.e., ChE inhibition) endpoints for the 2:1 and 1:1 mixtures studies did not coincide as expected. An interaction between CHP and CAR appears to depend on the ratio of compounds in the mixture as well as the biological endpoint.

Acaricide resistance in northern fowl mite (Ornithonyssus sylviarum) populations on caged layer operations in Southern California.

Southern California caged layer operations were visited over 3 yr. Northern fowl mites from 26 field populations were tested for acaricide resistance using a capillary pipette and glass dish bioassay. One was a susceptible field population with no pesticide exposure for over 30 yr (reference site for resistance ratio calculation). Technical and commercial formulations of malathion, carbaryl (Sevin), permethrin, and a commercial formulation of tetrachlorvinphos/dichlorvos (Ravap) were tested. Malathion did not have high activity for mites relative to other materials, but resistance to both technical and commercial formulations was low (< 5x). Resistance to other materials was moderate to extreme. Frequency of carbaryl resistance (> 10x) was higher with the commercial (88%) than the technical material (41%); 19% of the populations had resistance > 100x to commercial carbaryl. Frequency of Ravap resistance (> 10x) was 68%; 8% of populations had resistance > 100x. Frequency of permethrin resistance (> 10x) was 72% for the technical material and 88% for the commercial formulation. Extreme permethrin resistance (> 1,000x) was observed in 56 and 50% of mite populations assayed using the technical and commercial formulations, respectively. Among sites, resistance to permethrin was uncorrelated with resistance to other chemicals, suggesting a different resistance mechanism. Resistance to carbaryl and Ravap was highly correlated [r = 0.76 at the LC50 level (concentrations estimated to be lethal to 50% of the test population) and r = 0.99 at the LC95 level], suggesting a common resistance mechanism. Producers currently depend completely on pesticides to control mite infestations. Mite resistance to registered materials emphasizes the need for integrated control measures.

Time course of brain cholinesterase inhibition and recovery following acute and subacute azinphosmethyl, parathion and carbaryl exposure in the goldfish (Carassius auratus).

Laboratory toxicity data contrasting mortality and brain cholinesterase inhibition in the goldfish (Carassius auratus) are presented. Brain cholinesterase (ChE) was greatly reduced after 96 h of exposure in vivo at sublethal concentrations of azinphosmethyl and parathion. The inhibition of the enzyme was dose dependent, and concentrations higher than 0.1mg/L caused more than 90% inhibition. The effect of carbaryl was less pronounced, achieving an 86% inhibition at concentrations corresponding to the 96-h LC50. After in vivo exposure to sublethal concentrations of parathion and azinphosmethyl (0.1 mg/L) and carbaryl (3.0 mg/L), the activity of the goldfish brain ChE was greatly reduced. In the following 96 h of recovery, the enzyme inhibited with carbaryl was restored to 75% activity, while the enzyme inhibited with organophosphates (OPs) required more than 35 days for recovery. Goldfish were able to withstand high percentages of brain ChE inhibition without mortality, suggesting that another target may be responsible for the lethal effects. However, the enzyme is a good biomarker of acute and subacute exposure to OPs and carbamates.

Development of a toxic bait for control of eastern lubber grasshopper (Orthoptera: Acrididae).

This study assessed baits for eastern lubber grasshopper, Romalea guttata (Houttuyn). When offered a choice among several grain-based baits (rolled oats, wheat bran, oat bran, yeast, corn meal, cornflakes) and vegetable oils (canola, corn, peanut, soybean), eastern lubber grasshopper adults preferred bait consisting of wheat bran carrier with corn oil as an added phagostimulant. Other carriers were accepted but consumed less frequently. Discrimination by eastern lubber grasshoppers among oils was poor. Similarly, addition of flavorings (peppermint, anise, lemon, banana) resulted in few significant effects. The carbaryl, wheat bran, and oil bait developed in this study was effective at causing eastern lubber grasshopper mortality in field-cage studies. Significant mortality occurred even though grasshoppers had to locate dishes of bait in a large cage, and could feed on daylilies, or grass growing through the bottom of the cage, rather than on the bran flakes. Consumption of as little as a single carbaryl-treated bran flake could induce mortality, although individuals varied greatly in their susceptibility. The bait matrix developed in this study was readily consumed when in the presence of some plant species. We expect that wheat bran and corn oil bait would be most effective as protection for less preferred plants (tomato, pepper, eggplant, leek, parsley, fennel, daylily, lily of the Nile, and canna lily) because baits were readily consumed in the presence of these plants. Plants that are readily consumed in the presence of bait (preferred plants) included butter crunch lettuce, carrot, yellow squash, cauliflower, collards, green onion, chive, cucumber, cabbage, cantalope, endive, red leaf lettuce, society garlic, caladium, and amaryllis. Baits are likely to be less effective in the presence of such plants. On average, vegetables in Solanaceae (i.e., tomato, pepper, and eggplant) and Apiaceae (i.e., fennel and parsley) elicited high levels of bait-feeding activity, indicating that these vegetables were not highly preferred. The plants tested from Liliaceae, Cucurbitaceae, Asteraceae, and Brassicaceae elicited an intermediate-to-low level of bait feeding.

The relative toxicities of insecticides to earthworms of the Pheretima group (Oligochaeta).

An artificial soil test was used to determine the LC50 values of carbaryl, chlorpyrifos, imidacloprid, cyfluthrin and fipronil against earthworms of the Pheretima group. For a 24-h interval, carbaryl was the most toxic to earthworms (LC50 = 77 mg kg-1), followed by imidacloprid (155 mg kg-1), cyfluthrin (351 mg kg-1), chlorpyrifos (390 mg kg-1) and fipronil (> 8550 mg kg-1) as the least toxic. For the 48-h and 7-day intervals, imidacloprid was the most toxic to earthworms (LC50 = 5 mg kg-1 and 3 mg kg-1 respectively), followed by carbaryl (16 mg kg-1; 9 mg kg-1), cyfluthrin (128 mg kg-1; 110 mg kg-1), chlorpyrifos (330 mg kg-1; 180 mg kg-1) and the least toxic was fipronil (> 8550 mg kg-1 both intervals). The surface application rates required to achieve these values are compared with the rates recommended for the control of turfgrass pests.

Histological and ultrastructural studies of rats exposed to carbaryl.

The aim of the study was to assess the general toxic effects of dermally applied carbaryl, based on histological and ultrastructural examinations of internal organs and to relate these effects to earlier own studies where 14C carbaryl was used for determining the pesticide penetration. The pesticide was applied in doses of 1/5 and 1/10 LD50, administered to the tail skin of male Wistar rats 4 hours daily, for 4 weeks except Saturdays and Sundays. After the experiment, the animals were anaesthetized and the following organs were taken for histological study: brain, lung, heart, liver, kidney, skin from the site of exposure and skin from a place at least 2 cm distant from the exposure site. Lung, liver, kidney, heart and skin were used for ultrastructural studies. Dermal application of carbaryl resulted only in slight histological changes in skin, liver, brain and lung. Even in brain and liver, where large amounts of 14C carbaryl, compared to other organs (lung, kidney, heart), where the intensity of histologic changes was earlier stated to below. Ultrastructural changes were observed in skin, liver, lung, heart and kidney.

A randomization test-based method for risk assessment in neurotoxicology.

A current trend in risk assessment for systemic toxicity (noncancer) endpoints is to utilize the observable range of the dose-effect curve in order to estimate the likelihood of obtaining effects at lower concentrations. Methods to accomplish this endeavor are typically based on variability in either the effects of fixed doses (benchmark approaches), or on variability in the doses producing a fixed effect (probabilistic or tolerance-distribution approaches). The latter method may be particularly desirable because it can be used to determine variability in the effect of an agent in a population, which is an important goal of risk assessment. This method of analysis, however, has typically been accomplished using dose-effect data from individual subjects, which can be impractical in toxicology. A new method is therefore presented that can use traditional groups-design data to generate a set of dose-effect functions. Population tolerances for a specific effect can then be estimated from these model dose-effect functions. It is based on the randomization test, which assesses the generality of a data set by comparing it to a data set constructed from randomized combinations of single point estimates. The present article describes an iterative line-fitting program that generates such a data set and then uses it to provide risk assessments for two pesticides, triadimefon and carbaryl. The effects of these pesticides were studied on the locomotor activity of laboratory rats, a common neurobehavioral end point. Triadimefon produced dose-dependent increases in activity, while carbaryl produced dose-dependent decreases in activity. Risk figures derived from the empirical distribution of individual dose-effect functions were compared to those from the iterative line-fitting program. The results indicate that the method generates comparable risk figures, although potential limitations are also described.