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BACKGROUND: Various types of hydrogel compounds have recently been developed for controlling invasive and pest ants in a range of environmental settings including agricultural, urban and natural areas. The current study evaluated the potential of sodium polyacrylate (ACR) hydrogels to effectively deliver liquid baits to Argentine ants. RESULTS: Relative to standard polyacrylamide (PAM) hydrogels, individual ACR hydrogel particles were approximately five-fold heavier; this may affect how ants interact with the bait particles, and further influence bait uptake and efficacy. Additionally, ACR hydrogels had significantly higher water absorption capacity and significantly slower rate of water loss, especially during the first 2 h. The efficacy of ACR hydrogel bait containing 0.005% fipronil and various attractants was evaluated on laboratory colonies. Results demonstrated that ACR hydrogel acceptance is significantly increased by the addition of feeding attractants. In addition, a field trial was performed in a nature reserve invaded by Argentine ants to evaluate the efficacy of ACR hydrogel bait. The field trial demonstrated that ACR hydrogel bait containing 0.005% fipronil with various attractants is highly effective and that ant densities throughout the baited plots declined by >99% within 7 days. CONCLUSIONS: The results of this study demonstrate that: (i) fipronil is highly effective for Argentine ant control in natural areas when used in low concentrations (0.005%); (ii) ACR hydrogels are an effective tool for delivering liquid baits to Argentine ants; and (iii) hydrogel baits augmented with various attractants including salt, protein and pheromone are highly attractive to Argentine ants. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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This study aimed (1) to assess the ability of collembolans Folsomia candida to avoid soils contaminated with three seed dressing insecticides imidacloprid, clothianidin, and fipronil; (2) to assess the effects of the insecticides on collembolans' locomotion behavior; (3) to check if changes in the locomotion behavior would explain the avoidance/preference responses; and (4) to evaluate the possibility to use locomotion behavior as toxicity biomarker of the tested insecticides. Avoidance and locomotion behavior assays with collembolans F. candida were performed with commercial seed dressing formulations of three insecticides (imidacloprid, clothianidin, and fipronil). Results showed no avoidance behavior at any concentration, while a "preference" was observed with increasing concentrations of the three tested insecticides. Significant reductions in the locomotion of exposed collembolans were observed at ≥ 1 mg kg-1 for imidacloprid (18-38%) and fipronil (29-58%) and ≥ 4 mg kg-1 for clothianidin (10-47%). At the higher insecticide concentrations, the collembolans had their trajectories restricted to smaller areas, with a tendency for circular movements. Our results confirm that the "preference" for contaminated soils with neurotoxic substances is likely due to locomotion inhibition impairing the ability of organisms to escape. This effect highlights that only avoidance assays may be not sufficient to assure the safety of some substances and confirm the potential of locomotion behavior as a sensitive toxicity biomarker for neurotoxic insecticides.

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Reactive oxygen species (ROS) are generated as products of normal cellular metabolic activities; however, the use of pesticides to control leafcutter ants leads to unbalanced ROS production. We evaluated the effects of two insecticides (fipronil, sulfluramid) and metallic insecticide complex (magnesium complex [Mg(hesp)2(phen)] (1)) on the superoxide dismutase (SOD), glutathione (GSH) and the overall antioxidant capacity using two different methodologies: total radical-trapping potential (TRAP) and oxygen radical absorbance capacity (ORAC). Media workers of Atta sexdens (C. Linnaeus) were exposed to the insecticides for 24 h, 48 h, 72 h and 96 h before their fat bodies were dissected for analysis. The results showed that although the sulfluramid may cause the production of ROS, its slow action in the organism does not lead to oxidative stress. There is a rise in oxidative stress in workers of leafcutter ants treated with fipronil because SOD significantly increased when compared to the control group. On the other hand, Mg1-complex suppressed both GSH and SOD, indicating that the immune system may be affected by Mg1-complex, which has a delayed activity ideal for its use in chemical pest control. Both TRAP and ORAC evaluated total antioxidant capacities; however, ORAC proved to be a more sensitive method. In conclusion, the Mg1-complex is a new compound that should be further investigated as a potential replacement for fipronil and sulfluramid in pest control.

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RESUMEN El fipronil es uno de los pesticidas más importantes usados en agricultura y animales domésticos. A concentraciones muy bajas para el control de especies destino, también es tóxico para especies no destino, incluyendo a las abejas y numerosos macroinvertebrados acuáticos y terrestres. Estudios de laboratorio y campo han demostrado que tanto el fipronil, como sus productos de degradación, a concentraciones medioambientales observadas son suficientes para poner en peligro numerosos taxones de la comunidad acuática, incluidos los peces. En esta revisión se describen estudios de ecotoxicología cuyo impacto en especies no destino ha sido clave para que la Unión Europea prohibiese el fipronil para uso agrícola en 2013 y Estados Unidos lo haya restringido en muchos cultivos y actualmente lo esté revisando para renovar los distintos registros. En Colombia se siguen registrando al menos 60 productos a base de fipronil y desde agosto de 2021 se prohíbe su uso en plantaciones de aguacate, café, cítricos y pasifloras. En 2017, a raíz de la contaminación de huevos con fipronil en Europa, la Agencia Europea para la Seguridad de Alimentos publicó varios estudios sobre el riesgo para la salud humana que podía tener el consumo de huevos y carne de pollos con residuos de fipronil. La conclusión fue que la ingesta de fipronil a las concentraciones detectadas en huevos y carne no superaba niveles esperados que produjesen efectos adversos para la salud.

ABSTRACT Fipronil is one of the most important pesticides used in agriculture and domestic animals. At very low concentrations used for controlling target species, it is also toxic to nontarget species including bees and numerous aquatic and terrestrial macroinvertebrates. Laboratory and field studies have shown that both fipronil, and its degradation products, at relevant environmental concentrations are sufficient to endanger numerous taxa in the aquatic community, including fish. In this review, ecotoxicology studies are described that show significant impact on non-target species that have been instrumental to ban fipronil for agriculture in the European Union since 2013 and restricting many uses in the United States. In Colombia, at least 60 fipronil-based products continue to be registered and since August 2021 its use has been prohibited in avocado, coffee, citrus and ornamental flower plantations. In 2017, following the widespread contamination of eggs with fipronil across Europe, the European Food Safety Authority (EFSA) conducted several risk assessments for the consumption of eggs and chicken meat contaminated with fipronil residues. The conclusion was that the consumption of fipronil at the concentrations detected in eggs and meat did not exceed levels expected to pose health hazard for humans.

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The pyrethroid bifenthrin and the phenylpyrazole fipronil are widely employed insecticides, and their extensive use became an environmental issue. Therefore, this study evaluated their biodegradation employing bacterial strains of Bacillus species isolated from leaves of orange trees, aiming at new biocatalysts with high efficiency for use singly and in consortium. Experiments were performed in liquid culture medium at controlled temperature and stirring (32 °C, 130 rpm). After 5 days, residual quantification by HPLC-UV/Vis showed that Bacillus amyloliquefaciens RFD1C presented 93% biodegradation of fipronil (10.0 mg.L-1 initial concentration) and UPLC-HRMS analyses identified the metabolite fipronil sulfone. Moreover, Bacillus pseudomycoides 3RF2C showed a biodegradation of 88% bifenthrin (30.0 mg.L-1 initial concentration). A consortium composed of the 8 isolated strains biodegraded 81% fipronil and 51% bifenthrin, showing that this approach did not promote better results than the most efficient strains employed singly, although high rates of biodegradation were observed. In conclusion, bacteria of the Bacillus genus isolated from leaves of citrus biodegraded these pesticides widely applied to crops, showing the importance of the plant microbiome for degradation of toxic xenobiotics.

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γ-aminobutyric acid (GABA) is one of the main neurotransmitters involved in the adaptation processes against the damage that hypoxia can cause to the brain. Due to its antagonist action on GABA receptors, the insecticide fipronil can turn the fish more susceptible to the negative effects of hypoxia. This study aimed to understand better if fipronil affects these GABAergic responses of Tilapia ahead to hypoxia. Oreochromis Niloticus (Nile Tilapia) were exposed for 3 and 8 h to fipronil (0.0, 0.1, and 0.5 µg.L-1 ) under normoxia (dissolved O2 > 6 mg.L-1 ) and moderate hypoxia (dissolved O2 < 2 mg.L-1 ) conditions. Briefly, hypoxia caused opposite effects on the gene transcription of the evaluated ionotropic and metabotropic GABA receptors. Unexpectedly, we obtained reduced HIF1A mRNA and brain GABA levels, mostly in the first 3 h of the experiment, for the hypoxic group compared with the normoxia one. Besides that, we also demonstrated that the insecticide fipronil impairs the brain GABAergic signaling of a hypoxia-tolerant fish during the transition from a normoxic to an acute hypoxic state. Thus, these results predict the relevant impact on the brain metabolic adaptations of fishes exposed to such stressful conditions in an aquatic environment, as well as the effects of fipronil in the GABAergic responses to hypoxia, which in turn may have ecological and physiological significance to hypoxia-tolerant fishes exposed to this insecticide.

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This study evaluated the effects of environmental contamination caused by pasture intensification and pasture-sugarcane conversion on oxidative stress, biotransformation, esterase enzymes, and development of Scinax fuscovarious and Physalaemus nattereri. Tadpoles were exposed in mesocosms allocated in three treatments: (1) untreated extensive pasture (EP); (2) intensive-pasture conversion (IP) (2,4-D herbicide + fertilizers); and (3) pasture-sugarcane conversion (SC) (fipronil + 2,4-D + fertilizers). After 7 days of exposure, IP reduced catalase (CAT) and increased malondialdehyde (MDA) levels in P. nattereri, while this treatment decreased glucose-6-phosphate dehydrogenase (G6PDH) and CAT activities in S. fuscovarious. SC decreased CAT, G6PDH, and glutathione S-transferase (GST) activities in P. nattereri. In S. fuscovarius, SC reduced G6PDH, acetylcholinesterase (AChE), and carboxylesterase (CbE) activities. MDA was raised in both tadpole species exposed to SC, evidencing oxidative stress. Integrated biomarker responses showed higher scores in both species exposed to SC. Our results warn that management practices currently applied to sugarcane cultivation in Brazil can negatively impact the functional responses of amphibians at natural systems.

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Plant-derived chemicals are promising substances to control arthropod pests, although synthetic ones are still the most frequently used. Thus, comparative toxicological studies are needed to determine if natural substances are safe alternatives to replace the use of synthetic chemicals. This study aimed to compare the toxicity of carvacrol (natural origin), acetylcarvacrol (semi-synthetic) and a fipronil-based pesticide (synthetic). We assessed the effects of these chemicals on hemolytic activity, erythrocytes morphology and leucocyte viability using whole blood from human subjects. Additionally, DNA damage was evaluated through comet and DNA fragmentation assays. Fipronil and carvacrol caused hemolysis at concentrations ranging from 0.5 to 2.0%, whereas acetylcarvacrol did not cause hemolysis at 0.5 and 0.75%. Fipronil and carvacrol caused severe alterations in erythrocytes' morphology at 2%, such as ghost erythrocytes, elliptocyte-like shape and rouleau-like shape, presenting only 3.3 and 8.3% normal cells, respectively, at this concentration. However, 73.3% erythrocytes incubated with 2% acetylcarvacrol exhibited normal morphology. Fipronil considerably reduced leucocytes viability, decreasing it to 78% at 2%. Carvacrol and acetylcarvacrol showed no differences in leucocyte viability for 0.5 to 1.0%, but a decrease was observed for 2% carvacrol. The comet assay showed similar DNA damage for fipronil and carvacrol, but it was significantly lower for 1 and 2% acetylcarvacrol. Incubation with genomic DNA showed that only fipronil caused fragmentation of this molecule. Thus, we conclude that carvacrol and fipronil can present similar toxicity at higher concentrations. However, acetylation of carvacrol significantly reduced its toxicity to human blood cells compared with the other chemicals.

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Abstract Fipronil is an insecticide and acaricide widely used in agriculture and domestic animals worldwide. Ecotoxicology studies have shown that, even at the low concentrations used on target species, fipronil and its degradation products have a significant impact on non-target species, either by direct toxicity or indirect effects affecting the food chain. The negative effects of fipronil on non-target species of terrestrial and aquatic invertebrates and indirect effects on food chains have led to its use being banned or severely restricted in numerous countries, including all of the European Union, China, and the United States. Some of the species highly susceptible to fipronil are of great economic and ecological importance, including crayfish, brown shrimp, and bees. In particular, the impact on decimating bee hives worldwide is an example of fipronil´s undesirable effects on agriculture. Other species affected by fipronil -for which there are few studies- are biological predators of the same pests controlled by fipronil. Considering all the impacts on non-target species, the commercialization and indiscriminate use of fipronil in agriculture seem irresponsible. In Colombia, as of September 2021 and pressed by local beekeepers, the Instituto Colombiano Agropecuario (ICA) prohibited its use on avocado, coffee, citrus, and passiflower plantations. However, as long as its use is not prohibited in all agricultural applications, farmers could divert its use and continue using it in any other type of plantation. This paper describes the impact of fipronil on some of the beneficial invertebrate species of outmost economic and ecological importance.

Resumen El fipronil es un insecticida y acaricida ampliamente utilizado en la agricultura y los animales domésticos en todo el mundo. Los estudios ecotoxicológicos han demostrado que, aún a las bajas concentraciones utilizadas en las especies destino, el fipronil y sus productos de degradación tienen un impacto significativo en las especies no-blanco, ya sea por efectos tóxicos directos o indirectos que afectan la cadena alimentaria. Los peligros para las especies no-blanco de invertebrados terrestres y acuáticos y los efectos indirectos sobre las cadenas alimentarias han llevado a prohibir o severamente restringir su uso en numerosos países, incluyendo toda la Unión Europea, China y los Estados Unidos. Algunas de las especies altamente susceptibles al fipronil son de gran importancia económica y ecológica, incluyendo cangrejos de río, camarones y abejas. En particular, el impacto en la diezma de las colmenas de abejas en todo el mundo es un ejemplo de los efectos indeseables que tiene el fipronil en la agricultura. Otras especies afectadas por el fipronil -para las que existen pocos estudios- son los depredadores biológicos de las mismas plagas controladas por el fipronil. Teniendo en cuenta su impacto sobre las especies no-blanco, la comercialización y el uso indiscriminado de fipronil en la agricultura parecen irresponsables. En Colombia, a partir de septiembre de 2021 y presionado por los apicultores locales, el Instituto Colombiano Agropecuario (ICA) prohibió su uso en plantaciones de aguacate, café, cítricos y pasifloras. Sin embargo, mientras no esté prohibido su uso en todas sus aplicaciones agrícolas, los agricultores pueden desviar su uso y seguir utilizándolo en cualquier tipo de plantación. Este artículo describe el impacto del fipronil en sólo unas pocas especies de invertebrados beneficiosos de gran importancia económica y ecológica.

Resumo Fipronil é um inseticida e acaricídio amplamente utilizado na agricultura e animais domésticos em todo o mundo. Estudos de ecotoxicologia têm demonstrado que em baixas concentrações utilizadas em espécies-alvo, o fipronil e seus produtos de degradação têm um impacto significativo em espécies não-alvo, seja por efeitos diretos de toxicidade ou efeitos indiretos que afetam a cadeia alimentar. Os perigos para espécies não-alvo de invertebrados (terrestres e aquáticos) e efeitos indiretos sobre as cadeias alimentares levaram ao seu uso ser banido ou severamente restrito em vários países, incluindo toda a União Europeia, China e Estados Unidos. Algumas das espécies altamente suscetíveis ao fipronil são de grande importância econômica e ecológica, incluindo lagostim, camarão marrom e abelhas. Em particular, o impacto na dizimação das colmeias de abelhas em todo o mundo é um exemplo dos efeitos indesejáveis que o fipronil tem sobre a agricultura. Outras espécies afetadas pelo fipronil, para as quais há poucos estudos, são predadores biológicos das mesmas pragas controladas pelo fipronil. Considerando todos os impactos sobre espécies não-alvo, a comercialização e o uso indiscriminado do fipronil na agricultura parecem irresponsáveis. Na Colômbia, a partir de setembro de 2021 e pressionada por apicultores, a ICA proibiu seu uso em plantações de abacate, café, cítricos e maracujá. No entanto, desde que seu uso não seja proibido em todas as suas aplicações agrícolas, os agricultores podem desviar seu uso e continuar a usá-lo em qualquer tipo de plantação. Este artigo descreve o impacto do fipronil em apenas algumas espécies com grande importância econômica e ecológica.

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This study aimed to evaluate the sequence variations of the GABA-Cl gene of Rhipicephalus (Boophilus) microplus ticks from Argentina with different resistance levels to fipronil. Genomic DNA was obtained from engorged females (n = 50) of fipronil-susceptible and resistant tick field populations from five localities in northern Argentina. Tick populations were tested for fipronil resistance by in vitro larval packet test. DNA encoding amino acid residues 264-360 of the GABA-Cl was amplified by PCR. PCR products were sequenced and the translated amino acid sequences were aligned and compared among each other and with sequences of the GABA-Cl belonging to the Brazilian and Uruguayan reference strains fipronil-susceptible (Mozo) and resistant (RFSan and Juarez). All the GABA-Cl amino acid sequences obtained from the R. microplus specimens from Argentina were identical, regardless of the fipronil resistance-susceptibility status of each population. Mutations present in GABA-Cl sequence of RFSan and Juarez strains were not present in any of the populations from Argentina analyzed. These results indicate the failure of this gene as a molecular marker of resistance to fipronil, at least in the R. microplus populations from northern Argentina.

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Poultry production is linked to veterinary drug use to treat diseases. Few ectoparasitic compounds are approved for poultry. Fipronil is a pesticide widely used in agriculture. It is also a drug authorized to control ectoparasites in small animals and, in some countries, in cattle. There has been evidence of fipronil extra-label use in laying hens, mainly to control the red mite Dermanyssus gallinae. Fipronil's popularity is due to its high toxicity to invertebrates. It could be metabolized to more toxic metabolites that potentially damage human health. In the present study, we carry out a quantitative exposure assessment and risk characterization for fipronil residues in laying hen eggs for local consumption in five cities of Buenos Aires province in Argentina, namely, Azul, Balcarce, Juarez, Chaves, and Tandil. Consumption surveys and egg sampling were conducted for three summer periods. Eggs were analyzed by UFLC-MS-MS. Fipronil prevalence, residue concentrations, residue stability to cooking methods, egg consumption, among the most important variables were modeled. The results indicated that 20.7% of samples contained fipronil residues. The highest residue was fipronil sulfone metabolite. Fipronil concentrations quantified ranged between 10 and 2510 ppb (median value = 150 ppb). When eggs were cooked, fipronil residues were stable. The exposure assessment and risk characterization revealed that the highest probability of consuming eggs with fipronil residues above the admissible limits was for young adults (20.8%), followed by babies (16.9%), young children (16.4%), children (13.4%), teenagers (10.3%), older adults (9.41%), and adults (8.65%). These results suggest an unacceptable risk associated with egg consumption with fipronil residues for all age groups. PRACTICAL APPLICATION: Fipronil is widely used as an extra-label way on laying hens since its use is prohibited in poultry production both in Argentina and in most countries. This molecule has been classified as Class II, a moderately hazardous pesticide because it could damage various human organs. Fipronil residues in eggs could be one of the exposure pathways for consumers. Monitoring residual levels and carrying out the health risk assessment in eggs are thus in an urge.

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Carbon nanotubes (CNTs) have been increasingly more prevalent due to their use in product technology owing to their exceptional electrical and thermal conductivity and tensile strength because of their nanostructure and strength of the bonds among carbon atoms. The potential increase of CNTs in the environment is a concern, and studies to assess the toxic effects of these nanomaterials (NMs) are needed. However, so far, most of the studies are focused on aquatic species and much less is understood about the effects of NM in terrestrial organisms. This investigation used a functionalized multi-walled carbon nanotube (f-MWCNT) and the Jamaican cricket Gryllus assimilis to assess the effects of this NM. Cricket nymphs were injected with f-MWCNT suspension-at three different concentrations. The insecticide Fipronil was used as a positive control. Survival was monitored, and histological analysis was made in the brains. Pyknotic cells were quantified in two brain regions, a neurosecretory called Pars intercerebralis (PI), and an associative region called mushroom body (MB). No mortality was observed in any f-MWCNT concentration tested. A significant increase in pyknotic cells was observed as sub-lethal effect for the intermediate concentration of f-MWCNT, at PI, while any significant change was observed at the Kenyon cells of the MB. These results are discussed in the context of agglomeration and dispersion of the f-MWCNT at different concentrations, and availability of the f-MWCNT on the circulatory system, as well as the natural decay of pyknotic cells with time and different patterns of adult cricket neurogenesis. Our results showed that f-MWCNT had negative effects in the neurosecretory region of the brain.

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Fipronil is a current use pesticide, widely used in many crops, commonly adsorbed to sediments of aquatic environments. The purpose of this study was to evaluate the biomarker responses and fipronil distribution pattern in different matrixes (fish, sediment and water) after juveniles P. lineatus exposure at two environmental concentrations (5.5 and 82 µg kg--1) of fipronil-spiked sediments. The levels of oxidized proteins (PO), lipid peroxidation (LPO), and enzymatic activity of superoxide dismutase (SOD), reduced glutathione content (GSH), antioxidant capacity against peroxyls (ACAP) and acetylcholinesterase (AChE) were evaluated in liver, gills and brain. Concentrations of fipronil and its metabolites (f. desulfinyl, f sulphpHide and f. sulfone) were quantified by GC-ECD. F. desulfinyl was the major metabolite found in all matrixes, followed by f. sulphide in sediments, while f. sulfone was mainly accumulated in fish. Fipronil promoted oxidative stress in P. lineatus, as evidenced by the increases in LPO and PO levels and the decrease brain AChE activity. Fish exposed at both concentrations showed significant decrease in antioxidant capacity. Alterations in the antioxidant defenses system was evidenced in all organs. These results suggest that the occurrence of fipronil in aquatic environments can generate oxidative stress at different levels in P. lineatus, showing that this species is highly sensitive to the deleterious effects of fipronil and metabolites.

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The aim of the present study was to optimize a protocol for nuclear magnetic resonance (NMR) chiral discrimination to be used to determine the enantiomers ratio of agrochemicals. For this goal, the commercial agrochemicals fipronil and malathion were employed as active targets due the distinct physicochemical properties. We used the cyclodextrins to evaluate the chiral discrimination in aqueous media and chiral solvent agents to check in organic media. The fipronil chiral discrimination was accessed by ß-CD in aqueous solution, although this procedure was ineffective for malathion due the low solubility. In organic media, the NMR chiral discrimination was successful for both agrochemicals and sensitive to dilution process. The NMR experiments explore very sensitive nuclei, for instance 1 H, 19 F, and 31 P, in a simple, practical and low residue experimental protocol.

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Ants (Hymenoptera: Formicidae), especially the Argentine ant, Linepithema humile (Mayr), can be significant nuisance pests in urban and suburban environments. Conventional interventions have primarily relied on the use of chemical insecticides, namely fipronil and bifenthrin, applied as residual, contact treatments around the outside perimeter of infested structures. Despite tightening regulation limiting the scope of insecticide applications in urban settings, dependence on these products to manage ants continues, resulting in significant water contamination. The U.S. EPA, in response, has further restricted the use patterns of many insecticides used for ant control in professional and over-the-counter markets. The purpose of this review is to summarize the relevant literature associated with controlling nuisance pest ants, with emphasis on L. humile, without the use of liquid broadcast applications of EPA-registered insecticides while focusing on low-impact, alternative (to broadcast applications) pest control methods. Specific subsections include Trail Pheromone; Use of Behavior-Modifying Chemicals; Mass Trapping; Hydrogels, "Virtual" Baiting, and Exceedingly-Low Bait Concentrations; Food Source Reduction; Deterrents; and RNA Interference (RNAi).

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Argentine ants are one of the most common nuisance pest ants treated by pest management professionals (PMPs) in southern and western urban residential areas of the United States. Two new technologies (spraying with a pheromone adjuvant and using a biodegradable hydrogel bait delivery method) were used to develop a unique low-impact integrated pest management (IPM) protocol for Argentine ants in urban residential settings. The IPM protocol included a one-time perimeter spray treatment with 0.03% fipronil (mixed with a pheromone adjuvant) at the beginning of the ant season to achieve a quick knockdown. The initial spray application was followed by a biodegradable hydrogel baiting with 1% boric acid as a maintenance treatment. This low-impact IPM protocol was compared with two other conventional methods: (1) one initial fipronil application and one pyrethroid spray application for maintenance, or (2) one initial fipronil application and one essential oil insecticide spray application for maintenance. Based on Argentine ant foraging activity, the protocols were compared for their control efficacy. Insecticide use information and treatment time were also recorded and compared among different treatment protocols. Our results provided empirical data to support the effectiveness and economic feasibility of the low-impact IPM protocol for managing Argentine ants in urban residential settings.

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This experimental work reproduces the fipronil extra-label administration performed by producers in laying hens. The scientific goal was to characterize the residual concentrations in eggs from treated hens and suggest the withdrawal periods that should be respected to avoid risk for consumers. Thirty-four laying hens were allocated into two groups: Group A was treated with fipronil in feed, two single doses of 1 mg kg-1  day-1 ; Group B was administered a single dose of 1 mg kg-1 by the topical route. Fipronil egg residues were quantified by HPLC-MS/MS. Fipronil and its sulphone metabolite (fipronil-SO2 ) were measured in egg after both treatments. The highest egg residual profile was always for fipronil-SO2 . Mean maximum egg concentrations (Cmax ) of 228.5 ± 79.8 ng/g (fipronil) and 1,849 ± 867 ng/g (fipronil-SO2 ) were found after fipronil administration in feed. The lowest residual levels were quantified after the topical treatment with Cmax of 27.1 ± 4.9 and 163 ± 26 ng/g for fipronil and fipronil-SO2 . Mean fipronil marker residues and established MRLs allowed calculating the withdrawal periods, the shortest being 74 days after topical administration. Such a long withdrawal period is difficult to meet in egg production systems. Thus, the extra-label use of fipronil in laying hens should not be recommended under any circumstances.

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Fipronil was registered in Uruguay in 1997, and, since then, it has been used for the control of Haematobia irritans irritans and Rhipicephalus microplus. The susceptibility of H. irritants to this drug has not been evaluated. Therefore, the goal of the present study was to evaluate the resistance of H. irritans to fipronil. Additionally, a survey was carried out with the farmers to evaluate the use of fipronil for H. irritans control in the ranches where the flies came from. For the bioassays, 31 field populations of H. irritans were exposed to 10 concentrations of fipronil (3.2-16.0μg.cm2), and their LC50 values were calculated using probit analysis. A bioassay was performed with horn flies from the susceptible colony maintained at the USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Laboratory for comparison and calculation of resistance ratios (RRs). All 31 field populations surveyed in the study were susceptible to fipronil, with resistance ratios ranging from <0.5 to 2.2. Four populations with RRs >1 did not differ significantly from the susceptible strain. A single population showed an RR >2.2. Overall, the survey shows that fipronil was mostly used for R. microplus control, and in only three ranches, which were free of R. microplus, was fipronil used for horn fly control. Seventeen farmers did not use fipronil at all in the last three years. It is concluded that, in Uruguay, field populations of horn flies remain susceptible to fipronil.(AU)

O fipronil foi registrado no Uruguai em 1997 e, desde então, tem sido utilizado no controle de Haematobia irritans irritans e Rhipicephalus microplus. O objetivo do presente estudo foi avaliar a susceptibilidade de populações de campo de H. irritans ao fipronil. Além disso, foi realizada uma pesquisa para avaliar a utilização de fipronil e as práticas de controle de H. irritans nas fazendas de onde provinham as moscas. Para os bioensaios, 31 populações de campo de H. irritans foram expostas a 10 concentrações de fipronil (3,2-16,0μg.cm2), e seus valores de CL50 foram calculados usando análise probit. Um bioensaio foi realizado com H. irritans da colônia suscetível mantida no USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Laboratory para comparação e cálculo das razões de resistência (RRs). Todas as 31 populações de campo pesquisadas no estudo eram suscetíveis ao fipronil, com taxas de resistência variando de <0,5 à 2,2. Quatro populações com Rrs >1 não diferiram significativamente da cepa suscetível. Uma única população apresentou RR >2,2. No geral, o fipronil tinha sido usado principalmente para o controle de R. microplus, e em apenas três fazendas, que estavam livres de R. microplus, o fipronil era utilizado para o controle da H. irritans. Em 17 fazendas não tinha sido utilizado fipronil nos últimos três anos. Conclui-se que no Uruguai as populações de H. irritans no campo permanecem suscetíveis ao fipronil.(AU)

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Fipronil was registered in Uruguay in 1997, and, since then, it has been used for the control of Haematobia irritans irritans and Rhipicephalus microplus. The susceptibility of H. irritants to this drug has not been evaluated. Therefore, the goal of the present study was to evaluate the resistance of H. irritans to fipronil. Additionally, a survey was carried out with the farmers to evaluate the use of fipronil for H. irritans control in the ranches where the flies came from. For the bioassays, 31 field populations of H. irritans were exposed to 10 concentrations of fipronil (3.2-16.0μg.cm2), and their LC50 values were calculated using probit analysis. A bioassay was performed with horn flies from the susceptible colony maintained at the USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Laboratory for comparison and calculation of resistance ratios (RRs). All 31 field populations surveyed in the study were susceptible to fipronil, with resistance ratios ranging from <0.5 to 2.2. Four populations with RRs >1 did not differ significantly from the susceptible strain. A single population showed an RR >2.2. Overall, the survey shows that fipronil was mostly used for R. microplus control, and in only three ranches, which were free of R. microplus, was fipronil used for horn fly control. Seventeen farmers did not use fipronil at all in the last three years. It is concluded that, in Uruguay, field populations of horn flies remain susceptible to fipronil.(AU)

O fipronil foi registrado no Uruguai em 1997 e, desde então, tem sido utilizado no controle de Haematobia irritans irritans e Rhipicephalus microplus. O objetivo do presente estudo foi avaliar a susceptibilidade de populações de campo de H. irritans ao fipronil. Além disso, foi realizada uma pesquisa para avaliar a utilização de fipronil e as práticas de controle de H. irritans nas fazendas de onde provinham as moscas. Para os bioensaios, 31 populações de campo de H. irritans foram expostas a 10 concentrações de fipronil (3,2-16,0μg.cm2), e seus valores de CL50 foram calculados usando análise probit. Um bioensaio foi realizado com H. irritans da colônia suscetível mantida no USDA-ARS Knipling-Bushland U.S. Livestock Insects Research Laboratory para comparação e cálculo das razões de resistência (RRs). Todas as 31 populações de campo pesquisadas no estudo eram suscetíveis ao fipronil, com taxas de resistência variando de <0,5 à 2,2. Quatro populações com Rrs >1 não diferiram significativamente da cepa suscetível. Uma única população apresentou RR >2,2. No geral, o fipronil tinha sido usado principalmente para o controle de R. microplus, e em apenas três fazendas, que estavam livres de R. microplus, o fipronil era utilizado para o controle da H. irritans. Em 17 fazendas não tinha sido utilizado fipronil nos últimos três anos. Conclui-se que no Uruguai as populações de H. irritans no campo permanecem suscetíveis ao fipronil.(AU)

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