Application Of Chlorpyrifos Research Articles

Effect of insecticides alone and in combination with fungicides on nitrification and phosphatase activity in two groundnut (Arachis hypogeae L.) soils

The effect of selected pesticides, monocrotophos, chlorpyrifos alone and in combination with mancozeb and carbendazim, respectively, was tested on nitrification and phosphatase activity in two groundnut (Arachis hypogeae L.) soils. The oxidation of ammonical nitrogen was significantly enhanced under the impact of selected pesticides alone and in combinations at 2.5 kg ha(-1) in black soil, and furthermore, increase in concentration of pesticides decreased the rate of nitrification, whereas in the case of red soil, the nitrification was increased up to 5.0 kg ha(-1) after 4 weeks, and then decline phase was started gradually from 6 to 8 weeks of incubation. The activity of phosphatase was increased in soils, which received the monocrotophos alone and in combination with mancozeb up to 2.5 and 5.0 kg ha(-1), whereas the application of chlorpyrifos singly and in combination with carbendazim at 2.5 kg ha(-1) profoundly increased the phosphatase activity after 20 days of incubation, in both soils. But higher concentrations of pesticides were either innocuous or inhibitory to the phosphatase activity.

Field efficacy of wintertime insecticide applications against greenbugs, Schizaphis graminum (Rondani) (Hemiptera: Aphididae) on winter wheat ( Triticumaestivum L.)

Winter wheat producers in Oklahoma often combine an insecticide with a top-dress application of nitrogen during late fall and winter to control existing greenbug populations. We evaluated the efficacy of three classes of insecticides applied in cold weather field conditions ranging from −13.3 to 28.9 °C from 2002 to 2004 for greenbug control in winter wheat in replicated small plots. Insecticides provided control ranging from 0% to 98%, but generally responded similarly to temperature. Percent control of greenbugs resulting from applications of dimethoate, chlorpyrifos and λ-cyhalothrin was correlated with maximum, minimum and average daily temperatures that occurred two days post-treatment. While percent control was unique for each insecticide, a combined regression of percent control against average daily temperature predicted that a 95% level of control would be achieved when post-treatment temperatures exceeded 13.6 °C. Rainfall that occurred post-treatment affected the efficacy of dimethoate but did not affect the other insecticides. Insecticide persistence was extended under cooler temperatures, allowing acceptable control 14 days post-treatment if temperatures warmed. The decision to apply insecticides should be made based on existing treatment thresholds for greenbug, but if treatment with an insecticide is warranted, winter wheat producers can expect reasonable control of greenbugs from insecticides applied during the winter, as long as post-treatment temperatures exceed 13 °C within the following 14 days.

Effects of time‐variable exposure regimes of the insecticide chlorpyrifos on freshwater invertebrate communities in microcosms

The present study compared the effects of different time-variable exposure regimes having the same time-weighted average (TWA) concentration of the organophosphate insecticide chlorpyrifos on freshwater invertebrate communities to enable extrapolation of effects across exposure regimes. The experiment was performed in outdoor microcosms by introducing three different regimes: a single application of 0.9 µg active ingredients (a.i.)/L; three applications of 0.3 µg a.i./L, with a time interval of 7 d; and continuous exposure to 0.1 µg a.i./L for 21 d. Measurements showed that the TWA(21d) concentration in the continuous-exposure treatment (0.098 µg/L) was slightly lower than in the three-application (0.116 µg/L) and single-application (0.126 µg/L) treatments. The application of chlorpyrifos resulted in decreased abundances in the arthropod community, with the largest adverse effects reported for the mayfly Cloeon dipterum and cladocerans Daphnia gr. longispina and Alona sp., while smaller effects were observed for other insects, copepods, and amphipods. At the population level, however, the mayfly C. dipterum only responded to the single-application treatment, which could be explained by the toxicokinetics of chlorpyrifos in this species. At the end of the experimental period the invertebrate community showed approximately the same effect magnitude for all treatment regimes. These results suggest that for this combination of concentrations and duration of the TWA, the TWA concentration is more important for most species than the peak concentration for the assessment of long-term risks of chlorpyrifos.

Biomarkers of Chlorpyrifos Exposure and Effect in Egyptian Cotton Field Workers

BackgroundChlorpyrifos (CPF), a widely used organophosphorus pesticide (OP), is metabolized to CPF-oxon, a potent cholinesterase (ChE) inhibitor, and trichloro-2-pyridinol (TCPy). Urinary TCPy is often used as a biomarker for CPF exposure, whereas blood ChE activity is considered an indicator of CPF toxicity. However, whether these biomarkers are dose related has not been studied extensively in populations with repeated daily OP exposures.ObjectiveWe sought to determine the relationship between blood ChE and urinary TCPy during repeated occupational exposures to CPF.MethodsDaily urine samples and weekly blood samples were collected from pesticide workers (n = 38) in Menoufia Governorate, Egypt, before, during, and after 9–17 consecutive days of CPF application to cotton fields. We compared blood butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE) activities with the respective urinary TCPy concentrations in each worker.ResultsAverage TCPy levels during the middle of a 1- to 2-week CPF application period were significantly higher in pesticide applicators (6,437 μg/g creatinine) than in technicians (184 μg/g) and engineers (157 μg/g), both of whom are involved in supervising the application process. We observed a statistically significant inverse correlation between urinary TCPy and blood BuChE and AChE activities. The no-effect level (or inflection point) of the exposure–effect relationships has an average urinary TCPy level of 114 μg/g creatinine for BuChE and 3,161 μg/g creatinine for AChE.ConclusionsOur findings demonstrate a dose–effect relationship between urinary TCPy and both plasma BuChE and red blood cell AChE in humans exposed occupationally to CPF. These findings will contribute to future risk assessment efforts for CPF exposure.

A Rapid Detection of Pesticide Residue Based on Piezoelectric Biosensor

A piezoelectric biosensor made of macromolecular polymer and carboxyl multi-wall carbon nanotubes (MWNTs-COOH) coated with acetylcholinesterases (AChE) on the Ag-coated crystal surfaces was used to determine pesticide residue in freshly picked radishes 4 and 8 days post application of phoxim and chlorpyrifos. The sensitivity of the method was compared with gas chromatography. The results show that there is no significant difference between the two methods, which indicates that our method can be used to perform the same task as gas chromatography in analyzing pesticide residue. The device is more portable, less expensive and simpler to operate, which can be easily used for pesticide residue detection.

Impact of chlorpyrifos used for desert locust control on non-target organisms in the vicinity of mangrove, an ecologically sensitive area

Ecologically sensitive areas (ESAs) including the mangrove along the Red Sea Coast of Sudan may be subjected to adverse impacts of insecticides for controlling desert locust, Schistocerca gregaria (Acrididae). This study assessed potential impacts of an aerial application of chlorpyrifos (Ultra Low Volume [ULV], 279 g a.i. ha−1) during conditions resembling an operational treatment of desert locust. The surveyed non-target organisms were studied in one treated and one untreated area (88 ha each), during a 13-week pre-spray period and an 8-week post-spray period, from November 2001 to April 2002. Survival of caged prawns (Penaeidae) in the mangrove lagoon were tested in situ, and monitoring of relative abundances of non-target organisms included (i) terrestrial transect counts of hoopoe larks, Alaemon alaudipes (Alaudidae), and of antlion larval pits, Cueta spp. (Myrmeleontidae) and (ii) pitfall sampling of epigeal arthropods in the terrestrial zones from shore to cropland. The survival of Metapenaeus monoceros juvenile prawns fell dramatically between the third and fifth day after the application in the treated area compared to the untreated area, in which mortality was delayed. In the early mornings when control operations often occur, a northern and northwestern wind direction, i.e. from land towards the sea, dominates, thus adverse impact on the prawns is a risk. The abundance of antlion pits was reduced in the treated area following spraying, but not in the untreated. The same was true for observations of hoopoe larks, numbers of Mesostena angustata (Tenebrionidae), and Gryllus bimaculatus (Gryllidae), at species and family levels, and arachnids.

Telemetry‐based field studies for assessment of acute and short‐term risk to birds from spray applications of chlorpyrifos

In a program of avian field studies, radiotelemetry was combined with observations, carcass searches, residue analysis, and determination of brain acetylcholinesterase (AChE) activity to assess the acute and short-term risk posed by chlorpyrifos to birds. Studies were conducted in field crops (brassicas, Poland) and orchards (pome, Italy; citrus, Spain). In total, 25 individual applications of chlorpyrifos were studied on 13 sites. Before each application, birds were fitted with radio transmitters (with minimum stress to birds). Radiotagged birds were monitored and the avifauna observed before, during and for 7 d following each application. A total of 201 birds representing 19 species were radiotagged. In 80% of individual telemetric monitoring periods, birds remained at the study sites. No radiotagged birds showed any sign of intoxication. These included individuals who spent a major proportion of time within treated areas (some individuals located within treated area on >90% of occasions). A total of 7,238 bird sightings were recorded during constant observation during and immediately after application. An additional 4,017 sightings were recorded in 104 individual surveys during 7 d after each application. Two untagged birds (out of 11,255 bird sightings) exhibited atypical behavior for <1 min and 2 to 3 min, respectively, before flying away. This observation (for 0.02% of bird sightings) may or may not have been treatment related. Ten carcasses were recovered (none radiotagged). Residue analysis and brain AChE activity indicated that none was likely to have died from chlorpyrifos exposure. Radiotracking, supported by more traditional assessment methods, was effective for assessing impacts in the field. This extensive field program supports a conclusion that spray applications of chlorpyrifos present a low risk to birds.

Chlorpyrifos exposures in Egyptian cotton field workers

Neurobehavioral deficits have been reported in Egyptian pesticide application teams using organophosphorus (OP) pesticides, but whether these effects are related to OP pesticide exposures has yet to be established. In preparation for a comprehensive study of the relationship between OP pesticide dose and neurobehavioral deficits, we assessed exposure within this population. We conducted occupational surveys and workplace observations, and collected air, dermal patch and biological samples from applicators, technicians and engineers involved in chlorpyrifos applications during cotton production to test the hypotheses that: (1) dermal exposure was an important contributor to internal dose and varied across body regions; and (2) substantial differences would be seen across the three job categories. Applicators were substantially younger and had shorter exposure histories than did technicians and engineers. Applicators and technicians were observed to have relatively high levels of skin or clothing contact with pesticide-treated foliage as they walked through the fields. Both dermal patch loadings of chlorpyrifos and measurements of a chlorpyrifos-specific metabolite (TCPy) in urine confirmed substantial exposure to and skin absorption of chlorpyrifos that varied according to job category; and dermal patch loading was significantly higher on the thighs than on the forearms. These findings support our hypotheses and support the need for research to examine neurobehavioral performance and exposures in this population. More importantly, the exposures reported here are sufficiently high to recommend urgent changes in work practices amongst these workers.

Chlorpyrifos-based commercial formulation: alterations in corpuscles of Stannius of catfish

Corpuscles of Stannius (CS) and serum calcium of Heteropneustes fossilis were studied after exposure to Chlorpyrifos-Based Commercial Formulation (CBCF) for short-term (1.76 mg L−1 chlorpyrifos) and long-term (0.44 mg L−1 chlorpyrifos) application. The fish were sacrificed after 24, 48, 72 and 96 hours in short-term experiment and after 7, 14, 21 and 28 days in long-term experiment. Hypocalcaemia was noticed in CBCF-treated fish after both short- and long-term exposures. In CBCF-treated H. fossilis, AF-positive cells of CS exhibit increased granulation after 72 and 96 hours, the nuclear volume of these cells remains unchanged. The AF-negative cells of CS of CBCF-treated fish exhibit a slight increase in their nuclear volume after 96 hours. After 21 and 28 days, AF-positive cells of CS show increased granulation. Nuclear volume of these cells exhibited a decrease after 21 and 28 days. A few degenerating cells are also noticed. Nuclear volume of AF-negative cells of CS of CBCF-treated fish increase after 21 and 28 days.

Insecticide Management Strategies for Control of Swede Midge (Diptera: Cecidomyiidae) on Cole Crops

Insecticide field trials were conducted in Ontario, Canada, and New York state to identify insecticides effective against the swede midge, Contarinia nasturtii Kieffer (Diptera: Cecidomyiidae), a new invasive pest in North America. Field trials indicated that foliar applications of lambda-cyhalothrin, permethrin, acetamiprid, chlorpyrifos, and dimethoate could provide control of C. nasturtii. Foliar insecticide applications were effective in keeping damage within marketable limits in all cabbage and some broccoli trials during the early phase of regional colonization by C. nasturtii (2001-2002). However by 2005-2006, treatments were rarely able to maintain damage levels within marketable limits. Low efficacy suggested the possibility of insecticide resistance in Canadian C. nasturtii populations, but laboratory assays revealed no evidence for resistance. Thus, eventual control failures on a season-long basis were apparently due to very high populations during later phases of colonization in Ontario. Early season applications (e.g., seed treatments, greenhouse plug tray drenches and/or band sprays) of neonicotinoid insecticides proved effective for 3-5 wk after transplanting in New York. These early season treatments would require supplemental control with foliar insecticides, but would reduce the number of foliar applications required and thus reduce insecticide usage. Our results suggest that acceptable control with foliar insecticides will be difficult where C. nasturtii populations are high, because of multiple and overlapping generations, and difficulty in achieving adequate spray coverage. An integrated pest management program that uses cultural control methods and host plant resistance, with judicious use of insecticides, is needed for sustainable management of this newly invasive pest.

Brassinosteroids Promote Metabolism of Pesticides in Cucumber

Brassinosteroids (BRs) are known to protect crops from the toxicity of herbicides, fungicides and insecticides. It is shown here that application of 24-epibrassinolide (EBR) accelerated metabolism of various pesticides and consequently reduced their residual levels in cucumber ( Cucumis sativus L). Chlorpyrifos, a widely used insecticide, caused significant reductions of net photosynthetic rate (Pn) and quantum yield of PSII (Phi(PSII)) in cucumber leaves. EBR pretreatment alleviated the declines of Pn and Phi(PSII) caused by chlorpyrifos application, and this effect of EBR was associated with reductions of chlorpyrifos residues. To understand how EBR promotes chlorpyrifos metabolism, the effects of EBR on activity and expression of enzymes involved in pesticide metabolism were analyzed. EBR had a positive effect on the activation of glutathione S-transferase (GST), peroxidase (POD), and glutathione reductase (GR) after treatment with chlorpyrifos, although the effect on GR was attenuated at later time points when plants were treated with 1 mM chlorpyrifos. In addition, EBR enhanced the expression of P450 and MRP, which encode P450 monooxygenase and ABC-type transporter, respectively. However, the expression of GST was consistently lower than that of plants treated with only chlorpyrifos. Importantly, the stimulatory effect of EBR on pesticide metabolism was also observed for cypermethrin, chlorothalonil, and carbendazim, which was attributed to the enhanced activity and genes involved in pesticide metabolism. The results suggest that BRs may be promising, environmentally friendly, natural substances suitable for wide application to reduce the risks of human and environment exposure to pesticides.

Chemical control of white grub Liogenys fuscus (Blanchard 1851) (Coleoptera: Melolonthidae) in cornfields

Soil pests such as the white grub complex are of great importance in different Brazilian regions, and Liogenys fuscus (Blanchard) is the most common species at the Brazilian Western Central Region. Corn producers had largely relied on pesticides to keep initial pest outbreaks under control, however, there is little information regarding the efficacy of different insecticides to control L. fuscus. The objective of this research was to evaluate the effectiveness of some insecticides, applied either to the soil or the seed, in controlling L. fuscus in cornfields in State of Goias during two crop seasons. In 2004/2005 season the following chemicals were applied in furrow: chlorpyrifos (450, 675, 900, and 1170 g.ha-1); endosulfan (525 g.ha-1); and fipronil (160 g.ha-1). During the 2005/2006 season the treatments were chlorpyrifos (450 and 675 g.ha-1), fipronil (160 g.ha-1), both applied in furrow, as well as fipronil (37.5 and 50 g.100 kg of seeds-1) and thiamethoxan (70 g.100 kg of seeds-1) applied as seed treatment. The results showed that chlorpyrifos (450.0 g.ha-1) in furrow was effective to control L. fuscus. Plant stand and plant size in this treatment were 7-fold and 2-fold taller than plants in the control plots, during the 2004/2005 season. Similarly, fipronil 160.0 g.ha-1 applied in furrow had positive results, both outperforming endosulfan 525.0 g.ha-1 in furrow application. However, during the 2005/2006 season there was no benefit regarding plant stand or plant size due to insecticide application, and no pest injury was observed in the plants. During this crop season, results recorded for the seed treatment (fipronil 37.5 and 50 g.100 kg of seeds-1 and thiamethoxan 70 g.100 kg of seeds-1) were also similar to the chlorpyrifos and fipronil in furrow treatment, which may be considered to be used as a chemical control procedure. Therefore, under conditions similar to those prevalent during the execution of these trials, in furrow application of chlorpyrifos and fipronil as well as seed treatment with fipronil and thiamethoxan may be used to control L. fuscus outbreaks in cornfields.

Efeito da interação do nicosulfuron e chlorpyrifos sobre o banco de sementes e os atributos microbianos do solo

Considerando o período de competição de plantas daninhas e a incidência da lagarta-do-cartucho na cultura do milho, há necessidade de aplicação, em curto intervalo de tempo, de herbicidas e de inseticidas, principalmente o nicosulfuron e o chlorpyrifos. O objetivo deste estudo foi avaliar o efeito da aplicação sequencial do nicosulfuron e do chlorpyrifos sobre a emergência de plântulas do banco de sementes, a taxa de desprendimento de CO2 (respiração basal) e o C da biomassa microbiana (CBM) do solo. Foi realizada aplicação sequencial, em solo, do nicosulfuron (doses de 0 a 64 g ha-1) associado ou não ao chlorpyrifos (0 e 240 g ha-1). Aos 20, 40 e 60 dias após a aplicação (DAA) dos produtos, todas as plântulas emergidas do banco de sementes foram identificadas em nível de espécie, sendo estimadas a frequência, densidade e abundância, além do índice de valor de importância (IVI). Aos 60 DAA, determinou-se também a taxa de desprendimento de CO2, o CBM e o quociente metabólico (qCO2), por meio da relação entre o CO2 acumulado e o CBM total do solo. A aplicação alterou severamente a massa de plântulas secas e o número de espécies nas doses superiores a 20 g ha-1 do nicosulfuron. Na presença do herbicida, as espécies com maior IVI foram Boehavia diffusa e Commelina benghalensis. Quanto aos bioindicadores do solo, foi observado decréscimo na taxa da respiração basal do solo com o aumento da dose aplicada do nicosulfuron associado ao chlorpyrifos, sem efeito na ausência do inseticida. Houve decréscimo linear no CBM em todos os casos, independentemente da aplicação do chlorpyrifos; entretanto, observou-se uma taxa de decréscimo 4,5 vezes maior para o solo que recebeu esse inseticida em conjunto com o nicosulfuron. A avaliação do qCO2 confirmou o efeito negativo da aplicação do inseticida e do herbicida. Conclui-se que a aplicação de chlorpyrifos + nicosulfuron promove impacto negativo sobre o banco de sementes e sobre a atividade microbiana do solo.

Evaluation of Pheromone-Based Management Strategies for Dogwood Borer (Lepidoptera: Sesiidae) in Commercial Apple Orchards

The dogwood borer, Synanthedon scitula (Harris) (Lepidoptera: Sesiidae), is a serious wood-boring pest of apple in eastern North America. The recent identification of its sex pheromone and systematic documentation of the effect of a potent behavioral antagonist affords the opportunity to develop pheromone-based management strategies for this important pest. Here we evaluated the potential of pheromone-based mass trapping of males to reduce dogwood borer infestations and conducted preliminary evaluations of an antagonist-based pheromone blend for disruption of dogwood borer mate finding in commercial apple orchards in North Carolina, Virginia, and West Virginia. In the mass trapping study, treatments included a conventional trunk-drench application of chlorpyrifos, a low-density mass trapping regime of 5 traps/ha, a higher-density mass trapping regime of 20 traps/ha, and an untreated control. We removed large numbers of males from orchards at all locations, with 27,155, 8,418, and 7,281 removed from high-density trapping plots in North Carolina, Virginia, and West Virginia, respectively, over 2 yr. After 2 yr under each of these treatment regimes, infestation in high- and low-density mass trapping plots was not reduced to the level of chlorpyrifos-treated plots. An antagonist-based dispenser deployed at a rate of 250/ha effectively disrupted mate-finding by male dogwood borer. In plots with mating disruption dispensers, captures in pheromone-baited traps were virtually eliminated, and no males were captured in traps baited with virgin females.

Problems in Ceuthorrhynchus spp. Control on rapeseed in the region of Serbia

A global trend of intensive rapeseed production as a sustainable source of energy has also been accepted in our region, but intensified production results have increased pest populations in that crop. Central European countries with a long tradition of rapeseed production have ample data on pest biology, control and effects of insecticide applications, but such data are almost nonexistant under our regional conditions. In the light of this fact, the objective of our study was to determine the optimal time for insecticide applications for controlling pest species of the genus Ceuthorrynchus. Trials were set up using standard OEPP methods with certain adaptations concerning the pest species. The insecticides based on chlorpyrifos + bifenthrin, applied at the rates of 0.5 l/ha and 0.75 l/ha, and deltamethrin at 0.3 l/ha, were applied a) once - at maximum abundance of adults, and b) twice - first at maximum abundance, and then eight days later. The trials were set up at two localities - Kac and Kovilj. Insecticide effects were evaluated based on the number of adults per 20 plants, the number of damaged plants and the number of larvae per plant. After single application of the insecticides chlorpyrifos + bifenthrin (0.5 and 0.75 l/ha) and deltamethrin (0.3 l/ha) in the locality of Kac, the percentage of infested plants was 1.25%, 36% and 75% (respectively), and 95% in untreated plots; while 75% and 22.5% of the plants were infested in the locality of Kovilj after chlorpyrifos + bifenthrin application, 95% after deltamethrin application, and 97.5% in untreated plots. Insecticide effect estimated by the number of larvae/plant was 0 and 0.4 for chlorpyrifos + bifenthrin, 1.4 for deltamethrin and 3.3 for untreated surface in the locality of Kac; while in the locality of Kovilj the effect of chlorpyrifos + bifenthrin was 1.4 and 0.1, deltamethrin 3.9, and 5.2 larvae/plant in untreated plots. After two insecticide applications in Kac, the percentage of infested plants was 13.7% and 16.2% after chlorpyrifos + bifenthrin treatment, 62.5% after deltamethrin and 95% in untreated plots. In Kovilj, the percentage of infested plants was 22% and 17% after the application of chlorpyrifos + bifenthrin, 79% after deltamethrin, and 97.5% on untreated surface. The insecticide effect shown by the number of larvae/plant was 0.12 and 0.13 for chlorpyrifos + bifenthrin, 1.7 for deltamethrin and 3.3 on untreated surface in the locality of Kac. In Kovilj, the corresponding data were 0.16 and 0.08 for chlorpyrifos + bifenthrin, 1.4 for deltamethrin and 5.2 larvae/plant for the untreated surface.

Effect of chlorpyrifos on microbial biomass and activities in tropical clay loam soil

Clay loam soil from agricultural field of Gangetic alluvial zone of West Bengal was investigated to evaluate the effect of chlorpyrifos application at field rate (0.5 mg kg(-1) soil) and 100 times of the field rate (50 mg kg(-1) soil) on soil microbial variables under laboratory conditions. Acetone-induced stress on soil microorganisms was evident in the initial stages in terms of microbial biomass carbon (MBC) content in soil and basal soil respiration (BSR) in control soil samples which received acetone only as compared to control soil without acetone. The soil MBC content increased significantly by application of chlorpyrifos. The BSR and the fluorescein diacetate hydrolysing activity (FDHA) were not adversely affected by chlorpyrifos at field rate, whilst the chemical at higher dosage significantly decreased the metabolic activities of soil microbes in terms of BSR and FDHA.

Fate and effects of the insecticide chlorpyrifos in outdoor plankton‐dominated microcosms in Thailand

The fate and effects of the insecticide chlorpyrifos were studied in plankton-dominated, freshwater microcosms in Thailand. Disappearance rates of chlorpyrifos from the water column in the present study were similar to those in temperate regions. Insecticide accumulation in the sediment was relatively small, with the major part in the top layer (depth, 1.5 cm). Application of chlorpyrifos led to significant changes in freshwater biological communities. Clam shrimps (Conchostraca) and the cladoceran Moina micrura were the most susceptible species (no-observed-effect concentration [NOEC], 0.1 microg/L) and macroinvertebrates the most sensitive community (NOEC, 0.1 microg/L). These results are in agreement with those from semifield experiments with chlorpyrifos in temperate regions. The results of an in situ bioassay were used to calculate a NOEC of 0.1 microg/L and a 48-h median lethal concentration of 0.6 microg/L for M. micrura, which are similar to toxicity values reported for Daphnia magna in studies in temperate regions. Overall, these findings support the use of toxicity data from temperate regions for the risk assessment of low-persistent insecticides like chlorpyrifos for aquatic communities in tropical regions.

A novel approach to biological control with entomopathogenic nematodes: Prophylactic control of the peachtree borer, Synanthedon exitiosa

Generally, microbial control agents such as entomopathogenic nematodes are applied in a curative manner for achieving pest suppression; prophylactic applications are rare. In this study, we determined the ability of two Steinernema carpocapsae strains (All and Hybrid) to prophylactically protect peach trees from damage caused by the peachtree borer, Synanthedon exitiosa, which is a major pest of stone fruit trees in North America. In prior studies, the entomopathogenic nematodes S. carpocapsae and Heterorhabditis bacteriophora caused field suppression when applied in a curative manner to established S. exitiosa populations. In our current study, nematodes were applied three times (at 150,000–300,000 infective juveniles/tree) during September and October of 2005, 2006, and 2007. A control (water only) and a single application of chlorpyrifos (at the labeled rate) were also made each year. The presence of S. exitiosa damage was assessed each year in the spring following the treatment applications. Following applications in 2006, we did not detect any differences among treatments or the control (possibly due to a low and variable S. exitiosa infestation of that orchard). Following applications in 2005 and 2007, however, the nematode and chemical treatments caused significant damage suppression. The percentage of trees with S. exitiosa damage in treated plots ranged from 0% damage in 2005 to 16% in plots treated with S. carpocapsae (Hybrid) in 2007. In control plots damage ranged from 25% (2005) to 41% (2007). Our results indicate that nematodes applied in a preventative manner during S. exitios’s oviposition period can reduce insect damage to levels similar to what is achieved with recommended chemical insecticide treatments.

Effects of Repeated Applications of Chlorpyrifos on its Persistence and Soil Microbial Functional Diversity and Development of its Degradation Capability

Effects of repeated applications of chlorpyrifos on its persistence and soil microbial functional diversity were studied under laboratory conditions. The results showed that the degradation rate of chlorpyrifos increased whereas its inhibitory effect on soil microbial communities gradually decreased with application frequency of chlorpyrifos. A bacterial strain DSP capable of utilizing chlorpyrifos as a sole source of carbon and energy was isolated 21 days after the third chlorpyrifos application, which indicated that the capability of soil microorganism for degrading chlorpyrifos was formed during the experiment. It could be concluded that repeated applications of chlorpyrifos had no lasting impact on soil health.

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.