A dengue é um dos principais problemas de Saúde Pública da atualidade. É transmitida por mosquitos do gênero Aedes, sendo a espécie Aedes aegypti o vetor responsável pela transmissão no Brasil. O principal alvo de controle da doença é seu vetor, sendo o controle químico amplamente utilizado em todas as regiões atingidas. Como forma de prevenção ou em períodos de epidemia, torna-se necessária a eliminação dos mosquitos adultos, sendo indicada a nebulização a ultrabaixo volume (UBV) a frio do organofosforado malation por meio do uso de equipamentos pulverizadores acoplados a veículos. Este inseticida utilizado pode sofrer desvios durante e após a aplicação a UBV, caracterizando-se como um potencial agente de desequilíbrio ecológico, podendo atingir e gerar efeitos danosos em organismos não alvos aquáticos e terrestres. Este trabalho teve como objetivo desenvolver e validar um método de análise para o malation em cromatografia líquida de alta eficiência e obter recuperação do inseticida em níveis aceitáveis em água e solo, avaliar seu período de dissipação e tempo de meia vida (t1/2) nestas matrizes e classificá-lo quanto à toxicidade aguda e ao risco ambiental de acordo com diferentes autores, para o microcustáceo Daphnia magna, para a minhoca Eisenia foetida, para o peixe mato grosso (Hyphessobrycon eques) e para a macrófita Lemna minor. O método foi considerado adequado para análise do malation. A recuperação obtida para água foi de 97 por cento e para solo, 96 por cento . Efeitos tóxicos decorrentes da exposição ao inseticida foram observados para todos os organismos, sendo a Daphnia magna a espécie mais sensível aos testes de toxicidade aguda, com alto risco de intoxicação ambiental oriundo do uso peridomiciliar do malation. Em solo, o composto permaneceu na superfície com t1/2 de 4,5 h e sofreu lixiviação após ocorrência de chuva, sendo detectado por até 29 dias após a aplicação. Em água, o t1/2 foi de 0,1 h em pH 9.0 não sendo mais detectado a partir do segundo dia após aplicação. Em pH 7.0 e 5.0, esse período estendeu-se por até 7 dias, sendo o t1/2 de 3,2 e 4,4 d, respectivamente. / Dengue is one of the major public health problems nowadays. It is transmitted by mosquitoes of the genus Aedes, and the Aedes aegypti specie is the vector responsible for transmission in Brazil. The main target to control the disease is its vector, and the chemical control is widely used in all affected regions. As a preventive measure or in epidemic periods, it becomes necessary to eliminate adult mosquitoes, being indicated the ultralow volume nebulization of malathion organophosphate in cold way through the use of sprinklers attached to vehicles. This used insecticide can suffer deviation during and after application ULV, characterizing itself as a potential agent of environmental imbalance, with the possibility of reach and generate harmful effects on aquatic and terrestrial non-target organisms. This work had the objective to develop and validate a method of analysis for malathion in high performance liquid chromatography and obtain recovery of insecticide in acceptable levels in water and soil, evaluate its dissipation period and half-life time in these matrices and classify it on acute toxicity and environmental risk according to different authors, to the microcrustacean Daphnia magna, to the earthworm Eisenia foetida, to the fish Hyphessobrycon eques and to the macrophyte Lemna minor. The method was considered appropriate for analysis of malathion. The obtained recovery for water was 97 per cent and for soil, 96 per cent . Toxic effects resulting from exposure to the insecticide were observed for all organisms, resulting that Daphnia magna is the most sensitive species to the acute toxicity tests, with high risk of environmental intoxication originated from malathion peridomicilary use. In soil, the compound remained on the surface with t1/2 of 4.5 h and suffered lixiviation after rain occurrence, being detected for up to 29 days after application. In water, the t1/2 was 0.1 h in pH 9.0 and was not detected from the second day after application. In pH 7.0 and 5.0, this period was extended for up to 7 days, being the t1/2 of 3.2 and 4.4 d, respectively.

O presente estudo avaliou os efeitos letais e subletais de dipirona sódica e paracetamol para organismos de água doce. O efeito letal foi determinado pela realização de ensaios agudos com D. similis, C. dubia, C. silvestrii e D. rerio. A influência da temperatura, tipo de água de diluição e fotoperíodo na ecotoxicidade aguda foram avaliadas. Os efeitos subletais foram determinados por meio de ensaios de embrioxicidade com D. similis (20°C), crônicos individuais e populacionais com D. similis, C. dubia e C. silvestrii. A influência da temperatura na ecotoxicidade crônica individual e populacional foi determinada. Os critérios para aceitabilidade para o controle (número de neonatas) nos ensaios populacionais com D. simlis (20 e 25°C) e C. dubia, foram estabelecidos. Nos ensaios de ecotoxicidade aguda, D. similis (20°C) foi mais sensível a dipirona sódica que a 25°C e, para paracetamol, D. similis (25°C) foi mais sensível. A água de diluição influenciou na ecotoxicidade aguda apenas do paracetamol e o fotoperíodo não influenciou na ecotoxicidade aguda de ambos os fármacos. Os valores de CL(I);96H obtidos para D. rerio foram 3670 e 590mg.L-1 para dipirona sódica e paracetamol, respectivamente. Dipirona sódica e paracetamol induziram malformações nas neonatas e embriões de D. similis e os valores de CI50 obtidos foram 21,1 e 94,00mg.L-1, respectivamente. Os valores de CI50 nos ensaios crônicos individuais com dipirona sódica para D. similis (20°C e 25°C) foram 7,53mg.L e 8,08mg.L-1, respectivamente. Para C. dubia e C. silvestrii a CI50 para ensaios crônicos individuais com dipirona sódica foram 5,38 e 3,57mg.L-1, respectivamente. Nos ensaios crônicos individuais com paracetamol, a CI50 para D. similis (20°C) foi 21,84mg.L-1 e 10,72mg.L-1 para D. similis (25°C). Para C. dubia e C. silvestrii a CI50 nos ensaios crônicos individuais com paracetamol foram 7,24 e 4,15mg.L-1, respectivamente. Como critérios de aceitabilidade para os ensaios crônicos populacionais estabeleceu-se para o controle de D. similis (20 e 25°C) e C. dubia 137, 143 e 80 neonatas, respectivamente. Os valores de CI50 nos ensaios populacionais com D. similis (20 e 25°C), C. dubia e C. silvestrii para dipirona sódica foram 8,84, 10,82, 4,68 e 2,81mg.L-1, respectivamente. Para os ensaios populacionais com paracetamol os valores de CI50 para D. similis (20 e 25°C), C. dubia e C. silvestrii foram 9,57, 10,1, 6,48 e 4,26mg.L-1, respectivamente. Os valores das concentrações que causaram ecotoxicidade aguda e crônica não são superiores as concentrações destes compostos no ambiente porém, de acordo com a classificação baseada na Diretiva Européia 93/67/EEC, estes compostos são classificados como nocivos para o ambiente. / The present study evaluated the lethal and sublethal effects of dipyrone and paracetamol to different freshwater organisms. The lethal effect was determined by acute toxicity assays with D. similis, C. dubia, C. silvestrii and Danio rerio. The influence of temperature, type of dilution water and photoperiod were evaluated in acute toxicity assays. The sublethal effects were determined by Embryotoxicity with D. similis (20°C) and chronic toxicity assays both individual and population methods with D. similis, C. dubia and C. silvestrii. The influence of temperature upon individual and population chronic ecotoxicity was also determined. The criteria for acceptability for the population control assays with D. simlis (20 and 25°C) and C. dubia were established. D.similis (20°C) was more sensitive for dipyrone that 25 °C and for paracetamol, D.similis (25°C) was more sensitive. Dilution water interfere on acute ecotoxicity paracetamol, only and the photoperiod did not influence the acute ecotoxicity of both drugs. The LC(I);96H to Danio rerio was 3670mg.L-1 and 590mg.L-1 for dipyrone and paracetamol, respectively. Dipyrone and paracetamol induced malformations in D. similis neonates and embryos. The IC50 for these assays with dipyrone were 21,1mg.L-1 and 94mg.L-1 for tests with paracetamol. The IC50 of dipyrone to D. similis (20°C) was 7,53 and 8,08 at 25°C. Values of IC50 to C. dubia and C. silvestrii on individual chronic toxicity tests with dipyrona was 5,98 and 3,57mg.L-1respectively. The IC50 of paracetamol for D. similis (20°C) was 21,84 and 10,72mg.L-1 for at 25°C in individual chronic tests. The IC50 to C. dubia and C. silvestrii in individual chronic tests with paracetamol was 7,24 and 4,15mg.L-1 respectively. As criteria of acceptability for the population chronic tests were established to control the D. similis (20 and 25°C) and C. dubia, 137, 143 and 80 respectively. The IC50 obtained to D. similis (20 and 25°C), C.dubia and C.silvestrii for Dipyrone 8,84; 10,82; 4,68 and 2,81mg.L-1 respectively. For chronic population tests with paracetamol the IC50 to D. similis with 20 and 25°C, C.dubia and C.silvestrii was 9,57; 10,1; 6,48 and 4,26mg.L-1 respectively. The concentrations that cause acute and chronic ecotoxicity on organisms in this study are higher than environmental concentrations of these compounds. However, according to the classification based on the European Directive 93/67/EEC, these compounds are hazardous to the environment.

A dengue é um dos principais problemas de Saúde Pública da atualidade. É transmitida por mosquitos do gênero Aedes, sendo a espécie Aedes aegypti o vetor responsável pela transmissão no Brasil. O principal alvo de controle da doença é seu vetor, sendo o controle químico amplamente utilizado em todas as regiões atingidas. Como forma de prevenção ou em períodos de epidemia, torna-se necessária a eliminação dos mosquitos adultos, sendo indicada a nebulização a ultrabaixo volume (UBV) a frio do organofosforado malation por meio do uso de equipamentos pulverizadores acoplados a veículos. Este inseticida utilizado pode sofrer desvios durante e após a aplicação a UBV, caracterizando-se como um potencial agente de desequilíbrio ecológico, podendo atingir e gerar efeitos danosos em organismos não alvos aquáticos e terrestres. Este trabalho teve como objetivo desenvolver e validar um método de análise para o malation em cromatografia líquida de alta eficiência e obter recuperação do inseticida em níveis aceitáveis em água e solo, avaliar seu período de dissipação e tempo de meia vida (t1/2) nestas matrizes e classificá-lo quanto à toxicidade aguda e ao risco ambiental de acordo com diferentes autores, para o microcustáceo Daphnia magna, para a minhoca Eisenia foetida, para o peixe mato grosso (Hyphessobrycon eques) e para a macrófita Lemna minor. O método foi considerado adequado para análise do malation. A recuperação obtida para água foi de 97 por cento e para solo, 96 por cento . Efeitos tóxicos decorrentes da exposição ao inseticida foram observados para todos os organismos, sendo a Daphnia magna a espécie mais sensível aos testes de toxicidade aguda, com alto risco de intoxicação ambiental oriundo do uso peridomiciliar do malation. Em solo, o composto permaneceu na superfície com t1/2 de 4,5 h e sofreu lixiviação após ocorrência de chuva, sendo detectado por até 29 dias após a aplicação. Em água, o t1/2 foi de 0,1 h em pH 9.0 não sendo mais detectado a partir do segundo dia após aplicação. Em pH 7.0 e 5.0, esse período estendeu-se por até 7 dias, sendo o t1/2 de 3,2 e 4,4 d, respectivamente. / Dengue is one of the major public health problems nowadays. It is transmitted by mosquitoes of the genus Aedes, and the Aedes aegypti specie is the vector responsible for transmission in Brazil. The main target to control the disease is its vector, and the chemical control is widely used in all affected regions. As a preventive measure or in epidemic periods, it becomes necessary to eliminate adult mosquitoes, being indicated the ultralow volume nebulization of malathion organophosphate in cold way through the use of sprinklers attached to vehicles. This used insecticide can suffer deviation during and after application ULV, characterizing itself as a potential agent of environmental imbalance, with the possibility of reach and generate harmful effects on aquatic and terrestrial non-target organisms. This work had the objective to develop and validate a method of analysis for malathion in high performance liquid chromatography and obtain recovery of insecticide in acceptable levels in water and soil, evaluate its dissipation period and half-life time in these matrices and classify it on acute toxicity and environmental risk according to different authors, to the microcrustacean Daphnia magna, to the earthworm Eisenia foetida, to the fish Hyphessobrycon eques and to the macrophyte Lemna minor. The method was considered appropriate for analysis of malathion. The obtained recovery for water was 97 per cent and for soil, 96 per cent . Toxic effects resulting from exposure to the insecticide were observed for all organisms, resulting that Daphnia magna is the most sensitive species to the acute toxicity tests, with high risk of environmental intoxication originated from malathion peridomicilary use. In soil, the compound remained on the surface with t1/2 of 4.5 h and suffered lixiviation after rain occurrence, being detected for up to 29 days after application. In water, the t1/2 was 0.1 h in pH 9.0 and was not detected from the second day after application. In pH 7.0 and 5.0, this period was extended for up to 7 days, being the t1/2 of 3.2 and 4.4 d, respectively.

Poplar (Populus deltoides x nigra DN34) tissue cultures removed 2,4,6-trinitrotoluene (TNT) from an aqueous solution in five days, reducing the toxicity of the solution from highly toxic Microtox® EC value to that of the control. 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) was taken up by the plant tissue cultures more slowly, but toxicity reduction of the solution was evident. The measurement of toxicity reduction of aqueous solutions containing TNT and RDX was performed using a novel methodology developed for use with the Microtox® testing system. Radiolabeled TNT and RDX were used to confirm removal of explosives from hydroponic solutions containing plant tissue cultures and to verify that toxicity did not change in solutions where no plant cultures were present (positive controls). High Performance Liquid Chromatography (HPLC) and Liquid Scintillation Counter (LSC) measurements confirmed removal of TNT and RDX from solutions containing poplar plant tissue cultures and constancy of the plant-free controls. In addition, metabolites were identified in remediated solutions by HPLC, confirming the mechanism by which plants can remediate groundwater, surface water, and soil solutions. Using an Affymetrix® microarray, poplar trees were exposed to TNT over 48 hours. General patterns, as well as significant downregulated and upregulated genes were studied. We identified several new genes that were implicated in the detoxification and metabolism of TNT by Populus. In particular, our results support the "green liver" model of different gene families being expressed during the time course experiments. This suggests an alignment with Phase I transformation, Phase II conjugation, and Phase III compartmentation processes. Many of the genes identified in this study were related to those significantly expressed in previous Arabidopsis studies, supporting the comparison between these two plants. Gene families represented as significant in this study were glucosyltransferases, glycosyltransferases, cytochromes, and phosphofructokinases. We saw patterns in the areas of respiration, citric acid cycle, shikimatic pathway, and toxic responses.

This thesis examines the toxicity of the herbicide glyphosate (two formulations ¡V technical grade and Roundup Biactive RB) and the insecticide chlorpyrifos CPF to a model freshwater food chain of a producer and consumer. The importance of studying the toxicity of low (environmentally realistic) concentrations of pesticides to non-target organisms is highlighted. An extensive literature review on the toxicity of glyphosate and chlorpyrifos to aquatic organisms is provided. The requirements for the maintenance of algal (Chlorella vulgaris, Chlorella pyrenoidosa and Pseudokirchneriella subcapitata) and Daphnia carinata cultures are discussed. The effects of two formulations of the herbicide glyphosate (technical grade and Roundup Biactive„µ) and the insecticide chlorpyrifos on the growth of Chlorella pyrenoidosa and Pseudokirchneriella subcapitata were studied, and the EC50 values determined. Hormesis was observed when P. subcapitata was exposed to concentrations of Roundup equal to 7% and 4% of its EC50 respectively. When exposed to chlorpyrifos concentrations 0.3-5 ƒÝg/L, hormesis was observed for both algal species with a maximum at 0.06% of EC50. The effects of sublethal concentrations of chlorpyrifos on population characteristics of Daphnia carinata were investigated in multiple-generation toxicity testing using individual culture. Exposure to chlorpyrifos affected survival and fecundity of animals in the first generation. In the second generation the most affected endpoint was time to the first brood with an indication of hormesis. LC50 tests were then conducted using animals of the third generation from each of the exposures in individual tests. Results of testing the third generation showed a constant significant decline in LC50 in the order of control daphnids through to ¡¥0.1 LC50¡¦ pre-exposed daphnids. The same experimental protocol was used in testing of glyphosate (technical grade and Roundup Biactive). Glyphosate was tested in two different media: sea salt solution and M4 medium, while Roundup Biactive was tested in M4 medium. Results indicated that glyphosate and Roundup Biactive had low toxicity to Daphnia. Hormesis was evident in sea salt medium exposures in the first and second generations of daphnids with glyphosate. When exposed to glyphosate and Roundup Biactive in M4 medium animals showed no indication of hormesis. It is hypothesized that glyphosate may have compensated for the lack of microelements in the sea salt medium, and possible mechanisms discussed.The modifying effect of glyphosate on the toxicity of cadmium to Daphnia carinata was studied using the same experimental design. Low concentrations of Roundup Biactive reduced the toxicity of cadmium, and the performance of daphnia was enhanced in terms of animal size, survival, fecundity, and the rate of natural increase in both generations in the presence of glyphosate. However when the third generation was tested for their sensitivity to Cd in the 48-h LC50 experiments there was no difference between RB-free and RB-spiked treatments in pair wise comparisons, indicating that no adaptation mechanisms were involved in the enhancement. The implications of these observed effects for environmental freshwater food chains subjected to pesticide exposure are discussed and recommendations on modifying pesticide use are provided.

I present a simulation model that should be a useful tool for risk assessment of the impact of insecticide inhibitors of cholinesterase (ChE) applied in irrigated agricultural fields on non-target wildlife. I developed the model as a compartment model based on difference equations (Δt = 1 hour) and programmed with Stella® VII software. Conceptually the model is compartmentalized into six submodels describing the dynamics of (1) insecticide application, (2) insecticide movement into floodable soil, (3) irrigation and rain, (4) insecticide dissolution in water, (5) foraging and insecticide intake from water, and (6) ChE inhibition and recovery. To demonstrate application of the model, I simulate historical, current, and “worst-case” scenarios, that examined the impact of ChE-inhibiting insecticides on white-winged doves (WWDO - Zenaida asiatica) in the Lower Rio Grande Valley of Texas (LRGV), USA. To my knowledge, there are no field data verifying that the cause of ChE deprivation in WWDO is due to the ingestion of ChE-inhibiting insecticide residues dissolved in drinking water. I parameterized the model to represent a system composed of fields of cotton, sorghum, corn, citrus, and brushland that encompasses the activity range of a WWDO in the LRGV. I simulated situations representing the typical scenario of WWDO using irrigated crop fields in the absence and in the presence of rain. I also simulated “worst case” scenarios in which methyl parathion was applied at high rates and high frequency. Based on results of the simulations, I conclude that it is unlikely that WWDO are seriously exposed to ChE-inhibiting insecticides by drinking contaminated water. Only in rare cases, for example, when a rain event occurs just after the application of insecticides, are levels of ChE inhibition likely to approach diagnostic levels (20 %). The present simulation model should be a useful tool to predict the effect of ChE-inhibiting insecticides on the ChE activity of different species that drink contaminated water from irrigated agricultural fields. It should be particularly useful in identifying specific situations in which the juxtaposition of environmental conditions and management schemes could result in a high risk to non-target wildlife.

Complex chemical mixtures may be released into the environment from a variety of sources including hazardous waste sites. Components of chemical mixtures and their metabolites may be genotoxic leading to cancer and heritable gene mutations. Chemical analysis alone does not always provide the most accurate information from which to estimate the risk of adverse effects associated with exposure to mixtures. Current methods to estimate the human health risk for complex mixtures assume additive effects of the components. Although it is assumed that this approach is protective of human and ecological health, it is also recognized that chemical mixtures may induce a variety of interactions including potentiation, synergism, and antagonism. A combined testing protocol, using chemical analysis coupled with a battery of in vitro, in vivo, and in situ bioassays, provides the most accurate information from which to estimate risk. Such a combined testing protocol provides information to describe the major organic and inorganic constituents, as well as the pharmacokinetics and potential interactions of chemical mixtures. This research was conducted to investigate the potential genotoxic effects of complex chemical mixtures of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated aromatics (PCA) using microbial bioassays (Salmonella/microsome assay and the E. coli prophage induction assay), the 32P-postlabeling assay in mice, and in situ measurements of genotoxicity using flow cytometry. Samples of environmental media and wildlife tissues were collected from four National Priority List Superfund sites within the United States. In general, chemical analysis was not always predictive of mixture toxicity. Although biodegradation reduced the concentration of total and carcinogenic PAHs in soils and groundwater, the genotoxicity of extracts from environmental media did not display a corresponding reduction. Mixtures of polychlorinated biphenyls (PCBs) extracted from sediments were found to inhibit the genotoxicity of PAH mixtures when administered dermally to rodents. This inhibition exhibited a dose-response relationship, with the adduct frequency reduced at increasing doses of sediment extract. Finally, PAH concentrations in environmental media and tissues were found to correlate with DNA damage in wildlife receptors. An integrated approach, combining in vitro and in vivo methods to characterize genotoxicity provides more accurate information from which to estimate uptake and risk associated with exposure to complex mixtures and should be considered in both the human and ecological risk assessment process.

I present a simulation model that should be a useful tool for risk assessment of the impact of insecticide inhibitors of cholinesterase (ChE) applied in irrigated agricultural fields on non-target wildlife. I developed the model as a compartment model based on difference equations (Δt = 1 hour) and programmed with Stella® VII software. Conceptually the model is compartmentalized into six submodels describing the dynamics of (1) insecticide application, (2) insecticide movement into floodable soil, (3) irrigation and rain, (4) insecticide dissolution in water, (5) foraging and insecticide intake from water, and (6) ChE inhibition and recovery. To demonstrate application of the model, I simulate historical, current, and “worst-case” scenarios, that examined the impact of ChE-inhibiting insecticides on white-winged doves (WWDO - Zenaida asiatica) in the Lower Rio Grande Valley of Texas (LRGV), USA. To my knowledge, there are no field data verifying that the cause of ChE deprivation in WWDO is due to the ingestion of ChE-inhibiting insecticide residues dissolved in drinking water. I parameterized the model to represent a system composed of fields of cotton, sorghum, corn, citrus, and brushland that encompasses the activity range of a WWDO in the LRGV. I simulated situations representing the typical scenario of WWDO using irrigated crop fields in the absence and in the presence of rain. I also simulated “worst case” scenarios in which methyl parathion was applied at high rates and high frequency. Based on results of the simulations, I conclude that it is unlikely that WWDO are seriously exposed to ChE-inhibiting insecticides by drinking contaminated water. Only in rare cases, for example, when a rain event occurs just after the application of insecticides, are levels of ChE inhibition likely to approach diagnostic levels (20 %). The present simulation model should be a useful tool to predict the effect of ChE-inhibiting insecticides on the ChE activity of different species that drink contaminated water from irrigated agricultural fields. It should be particularly useful in identifying specific situations in which the juxtaposition of environmental conditions and management schemes could result in a high risk to non-target wildlife.

The western burrowing owl, Athene cunicularia hypugaea, is a Federal Species of Concern, whose numbers and range have been drastically reduced from historic levels in Texas. Burrowing owls roost and forage in agricultural areas, and it has been hypothesized that exposure to insecticides may be a factor in the decline of their population. Burrowing owls wintering in southern Texas use agricultural culverts in cotton fields as roost sites, which may increase their risk of exposure to agricultural chemicals, either through ingestion of contaminated prey or through dermal exposure to agricultural runoff. Simulation modeling was used to characterize the risks to individual burrowing owls wintering in agricultural landscapes in southern Texas due to effects of exposure to insecticides or other agricultural chemicals. The simulation model was created using Stella® VII software (High Performance Systems, Inc., New Hampshire, USA). The model is broken into four submodels simulating (1) foraging behavior of burrowing owls, (2) chemical applications to crops, (3) chemical transfer and fate in the crop soil and prey items, and (4) chemical exposure in the burrowing owl. This model was used to evaluate (1) which components of the model most affect the endpoints, (2) the relationship between increased concentrations of agricultural chemicals in culverts and subsequent lethal and sublethal effects from dermal exposure to agricultural runoff, and (3) which agricultural chemicals have the greatest potential to cause adverse effects in burrowing owls. Model results suggested (1) the half-lives of agricultural chemicals in birds caused the most variation in the results, and data gaps exist for several important model components (2), exposure to increased concentrations of agricultural chemicals in culverts is unlikely to result in lethal effects, but is likely to lead to sublethal effects in burrowing owls, and (3) the chemicals with the greatest potential to negatively affect burrowing owls wintering in southern Texas are the OP insecticides chlorpyrifos, dicrotophos, and disulfoton, the oxadiazine insecticide indoxacarb, the herbicide trifluralin, and the defoliants tribufos and paraquat. The results of this model demonstrate the usefulness of simulation modeling to guide future research related to the conservation of burrowing owls.

No description available.