RESUMO
The German cockroach, Blattella germanica L., is a hemimetabolous insect pest of economical and medical importance. N,N-diethyl-3-methylbenzamide (DEET) is an insect repellent whose effect on this species has received very little attention. The objective of this work was to determine whether the behavioral response of B. germanica to DEET varies along its life cycle. DEET repellence was assessed in small, medium, and large nymphs, and in adults of both sexes, all originated from the same laboratory colony (CIPEIN). The experimental arena consisted in a piece of filter paper treated with repellent on one half (195 µg/cm2) and solvent alone on the other half. A cockroach was placed on the filter paper, and its behavior was filmed. An image analyzer was used to quantify how long the insect spent on each side of the paper. As a control, a cockroach was exposed to a piece of filter paper treated with solvent (acetone) alone. Each assay was repeated independently six times. Distribution coefficient (DC) values were calculated, a parameter that ranges between 0 (attraction) and 1 (repellence). Small nymphs were more sensitive to DEET (mean DCâ =â 0.93). The mean DC values of the other groups varied between 0.62 (medium nymphs) and 0.71 (male adults). The group of medium nymphs was the only one whose behavior was not significantly altered by exposure to DEET. The results show the importance of assessing insect repellents at different stages of the insect's life cycle in order to obtain a complete panorama of its effect.
Assuntos
Blattellidae , Repelentes de Insetos , Acetona , Animais , DEET , Masculino , NinfaRESUMO
Monoterpenes are the main components of essential oils. Some members of this chemical family present insecticidal activity. Triatoma infestans (Klug) is the main vector of Chagas disease in Argentina, Bolivia, Paraguay, and Perú. The objective of this work was to evaluate the effect of six monoterpenes (1,8-cineole, eugenol, linalool, menthol, α-terpineol, and thymol) on the locomotor and flushing out activity of T. infestans. A video tracking technique was used to evaluate the locomotor activity of nymphs exposed to different concentrations of these chemicals applied as films on filter paper. Papers treated with acetone alone were used as negative controls, while solutions of tetramethrin were applied as positive controls. Only linalool and menthol produced hyperactivation. Flushing out was assessed under laboratory conditions using a standardized aerosolization method. All monoterpenes were applied at 1.5 g/m3. 1,8-Cineole, α-terpineol, and thymol flushed out 10% or less nymphs. The average flushing out produced by eugenol was 36.7%. Values of median flushing out time (FT50) could only be calculated for linalool and menthol (16.67 and 42.98 min, respectively). The FT50 value for the positive control tetramethrin (applied at 0.006 g/m3) was 8.29 min. Following these results, the flushing out activity of a mixture of linalool and eugenol was evaluated. The FT50 of this 2:1 linalool:eugenol mixture was 40.73 min. Finally, flushing out assays performed in semifield conditions showed similar results to those obtained at the laboratory.
Assuntos
Controle de Insetos , Inseticidas , Monoterpenos , Piretrinas , Triatoma , Monoterpenos Acíclicos , Animais , Eugenol , Ninfa/crescimento & desenvolvimento , Triatoma/crescimento & desenvolvimentoRESUMO
Resistance to pesticides has been studied in several insect pests, but information on the natural enemies of pests-including the Neotropical predator Chrysoperla externa Hagen (Neuroptera: Chrysopidae), a major biological control agent in South America-is lacking. We report here a comparative study between a field-collected strain of C. externa subjected to monthly sprayings of pyrethroids and neonicotinoids and a laboratory strain without exposure to pesticides. The tolerance of both strains against zeta-cypermethrin was similar, and addition of the synergist piperonyl butoxide increased the toxicity by 30% in both strains. Gas-chromatography analyses and mixed-function-oxidase measurements indicated similar values in both strains and also confirmed the key role of oxidative metabolism in this species. Because C. externa has maintained a tolerance to zeta-cypermethrin without previous pesticide exposure, this species could potentially be mass-reared and released in fields in the presence of pesticide pressure.
Assuntos
Insetos , Inseticidas/metabolismo , Piretrinas/metabolismo , Animais , América do SulRESUMO
The cerambycid beetle Hedypathes betulinus (Klug) (Coleoptera: Cerambycidae) causes severe damage to yerba mate plants (Ilex paraguariensis (St. Hilaire) (Aquifoliales: Aquifoliaceae)), which results in large losses of production. In this study, the pathogenicity of entomopathogenic fungi of the species Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Hypocreales: Cordycipitaceae), Metarhizium anisopliae sensu lato (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae), and Purpureocillium lilacinum (Thom) Luangsa-ard, Hywel-Jones, Houbraken and Samson (Hypocreales: Ophiocordycipitaceae) on yerba mate were evaluated. Fifteen isolates of B. bassiana, two of M. anisopliae, and seven of P. lilacinum on H. betulinus adults were analyzed under laboratory conditions. The raw mortality rate caused by B. bassiana isolates varied from 51.1 to 86.3%, and their LT50 values varied between 8.7 and 13.6 d. The isolates of M. anisopliae caused 69.6â81.8% mortality, and their LT50 values varied between 7.4 and 7.9 d. In contrast, isolates of P. lilacinum were not pathogenic. M. anisopliae and B. bassiana isolates were pathogenic against H. betulinus adults, suggesting that they may be useful in biological control programs for insect pests of yerba mate.
Assuntos
Beauveria/fisiologia , Besouros/microbiologia , Hypocreales/fisiologia , Metarhizium/fisiologia , Animais , Ilex paraguariensis/parasitologia , Controle Biológico de VetoresRESUMO
The generalist predator Chrysoperla externa (Neuroptera: Chrysopidae) is distributed in the Neotropical Region and presents a strong potential as a biological control agent due to its easily rearing, high voracity and tolerance to several pesticides. This species feeds on relevant pests such as aphids, whiteflies, trips and various lepidopterans. In Argentina, an indiscriminate chemical control with broad spectrum pesticides is still the first option for controlling pests causing resistance problems and reduction of beneficial organisms. Therefore, it would be desirable that predators or parasitoids develop tolerance or resistance as phytophagous pests for their maintenance in the agricultural ecosystems. The objective of this work was to evaluate the tolerance of C. externo to the pyrethroid cypermethrin by topical exposure in laboratory conditions. The symptoms evaluated were tremors, movement, knockdown, inability to walk due to being glued. Recovery from poisoning symptoms was also evaluated. Six different concentrations of the pesticide, including the full field one, were tested. The exposure method was by topical applications on third larval instar. A low toxicity on larvae at 24 h post-treatment was observed, even at the highest concentration evaluated. Most of treated individuals looked normal at 24 h post-treatment; those who were knocked down showed a complete recovery between 48 and 72 h post-treatment. C externa demonstrated a high tolerance to pyrethroids. This could be due to the activity involved in pyrethroids biotransformation (for example, esterases and mixed-function oxidases), or to a low sensitivity of the molecular target. Future studies should be addressed at biochemical and molecular levels to complete our knowledge about insecticide effects on this predator.
Assuntos
Insetos/efeitos dos fármacos , Inseticidas/toxicidade , Piretrinas/toxicidade , Animais , Argentina , Comportamento Animal/efeitos dos fármacos , Bioensaio , Ecossistema , Insetos/crescimento & desenvolvimento , Insetos/fisiologia , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Larva/fisiologiaRESUMO
Volatile emissions of adult male Triatoma infestans were collected on non-polar SPME fibers and analyzed by gas chromatography linked to a mass spectrometer. A complex mixture of 16 short-chain esters and acids were identified. The composition of short-chain aliphatic acids (ethanoic to nonanoic acids) was similar to previously reported results. The most abundant aliphatic acid was 2-methylpropanoic acid, constituting 18% of the total volatile content. Also abundant were the esters 2- and 3-methylbutyl 2-methylpropanoate, which constituted 30% and 22%, respectively, of the total volatile content. A similar pattern of compounds was observed in the volatiles secreted by dissected male Brindley's glands; however, in this case, 2- and 3-methylbutan-1-ol were detected which were not found in live insect volatile emissions. Large variability in volatile composition was also observed among the glands excised from different insects. Electroantennographic (EAG) evaluation of the components of Brindley's gland showed significant responses for 2- and 3-methylbutyl 2-methylpropanoate compared to controls. The mixture of volatiles secreted by excised Brindley's glands and the isolated 2- and 3-methylbutyl 2-methylpropanoate had repellent effects on both male and female T. infestans, possibly associated with a defensive strategy.
Assuntos
Feromônios/análise , Glândulas Odoríferas/metabolismo , Triatoma/metabolismo , Animais , Feminino , Cromatografia Gasosa-Espectrometria de Massas , Masculino , Feromônios/química , Feromônios/metabolismo , VolatilizaçãoRESUMO
The biological activities of ethanol and petroleum ether extracts from leaves and fruits of Schinus molle against adults of Blattella germanica were examined by repellence test and topical application. All extracts produced significant repellent effect and mortality.
Assuntos
Anacardiaceae , Blattellidae/efeitos dos fármacos , Inseticidas/farmacologia , Fitoterapia , Extratos Vegetais/farmacologia , Animais , Relação Dose-Resposta a Droga , Frutas , Inseticidas/administração & dosagem , Inseticidas/uso terapêutico , Masculino , Extratos Vegetais/administração & dosagem , Extratos Vegetais/uso terapêutico , Folhas de PlantaRESUMO
The behavioural responses of the haematophagous bug Triatoma infestans towards some previously identified components of its faeces: 4-methylquinazoline, 2,4- dimethylquinazoline and their mixtures were evaluated using a video tracking system. Fifth instar nymphs and females but not males were significantly attracted to polyethylene glycol formulations of 4-methyl + 2,4-dimethylquinazoline (50 microg each). Fifth instar nymphs were also attracted to 4-methylquinazoline alone (50 microg) but females were only attracted by the mixture of both methyl quinazolines (50 microg each). Syntheses of both methyl quinazolines were carried out starting from 2-aminoacetophenone by modifying the conditions of reported procedures.
Assuntos
Comportamento Animal/efeitos dos fármacos , Quinazolinas/farmacologia , Triatoma/efeitos dos fármacos , Animais , Bioensaio , Feminino , Masculino , Ninfa/efeitos dos fármacos , Quinazolinas/químicaRESUMO
Permethrin has been used extensively for control of Pediculus humanus capitis De Geer (Anoplura: Pediculidae) in Argentina since 1990, resulting in the development of resistance to this and other pyrethroids. This resistance was first detected in some field populations in 1997. A survey for resistance in Buenos Aires in 2001 revealed significant resistance levels in lice on children at 24 of 26 (92.3%) schools. When compared with a previously unexposed reference population, resistance ratios (RRs) obtained by exposing the insects to filter papers impregnated with permethrin ranged from 2 to 60 in 10 (39%) of the schools. RRs in the remaining 14 (61%) populations were too great to not be measured with the filter paper method (RR > 88.7). As an alternative, we used topical applications of 0.1 microl of acetone solution of permethrin on the dorsal abdomen of adults and third instars. This topical method, which has not been previously reported for head lice, was capable of quantifying higher levels of resistance. Highly resistant populations had RRs from 162.5 to 655.2. When applied to populations with low and intermediate levels of resistance, results from the filter paper and topical application methods were highly correlated, and RRs from topical application were higher than those from the filter paper method. Results from the combination of the two methods indicated that head lice among Buenos Aries school children are highly resistant to permethrin, and the resistance is widespread.
Assuntos
Resistência a Medicamentos/fisiologia , Inseticidas/toxicidade , Pediculus/fisiologia , Permetrina/toxicidade , Animais , Argentina , Bioensaio/métodos , Criança , Humanos , Infestações por Piolhos , Instituições AcadêmicasRESUMO
The hyperactivity, incoordination, recovery, and mortality produced by four alpha-cyanopyrethroids usually used for Chagas disease vector control (beta-cypermethrin, beta-cyfluthrin, lambda-cyhalothrin, and deltamethrin) were evaluated on third instar nymphs of Rhodnius prolixus. All pyrethroids modified the locomotor activity of the nymphs, which increased linearly as a function of the log of insecticide concentration. lambda-Cyhalothrin showed the lowest values of Effective Concentration 50%, Lethal Concentration 50%, Effective Time 50%, and Lethal Time 50% when insecticides were applied by contact with treated filter papers. Recovery from incoordination was observed after topical application of the insecticides. The recovery was inhibited by the simultaneous application of piperonyl butoxide, suggesting that biotransformation by mixed-function microsomal oxidases is involved in the process of recovery.