Abstract:

For many years it has been accepted that DEET interferes with the detection of odours from the host instead of having a repellent effect. However, recent work showed that DEET acts as an odorant molecule and elicits a behavioural response in the absence of other stimuli. Therefore, DEET must promote some phenomenon connected with the stimuli-sensory system interaction, such as a sensory adaptation, where the sensory system regulates its sensitivity to different stimuli intensities during continuous or repetitive exposure. In this work, we studied different aspects of the insect-DEET interaction through behavioural observations. Previous exposure of fifth instar Rhodnius prolixus nymphs to DEET decreased the behavioural response to this repellent. We observed a decrease in repellence after different times of continuous stimulation with DEET in a time-dependent manner. The response to DEET was recovered 10. min after exposure, when insects were continuously stimulated during 5 or 10. min; maximum repellence was recovered 20. min after exposure when insects were stimulated for 20. min. DEET produced a repellent effect when nymphs were exposed only to its vapours. These results suggest that exposure to DEET produces adaptation in R. prolixus nymphs, and that the behavioural response elicited by DEET occurs via olfaction when no other stimuli are present.

Author affiliation: Sfara, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina

Author affiliation: Mougabure Cueto, Gastón Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina

Author affiliation: Zerba, Eduardo Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Universidad Nacional de San Martín. Instituto de Investigación en Ingeniería Ambiental; Argentina

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Universidad Nacional de San Martín. Instituto de Investigación en Ingeniería Ambiental; Argentina

Abstract:

N , N -diethyl-3-methylbenzamide (DEET) is a broad-spectrum insect repellent used by millions of people since the 1950s. Ethyl 3-[acetyl(butyl)amino]propanoate (IR3535) is a repellent developed more recently that is still not used as extensively. This study compares the behavioral and toxicological effects of both substances in fifth-instar nymphs of the blood-sucking bug Rhodnius prolixus Stål (Hemiptera: Reduviidae), one of the main vectors of American trypanosomiasis (Chagas disease) . Repellency was quantified using filter paper discs as experimental arenas. Half the discs were treated with solution of repellent in acetone, and the other half with acetone alone. The lowest observed effect level was identical for both substances, 74 µg/cm 2 . Nymph age (between 1–3 h and 99 d from last ecdysis) had no influence on repellency. Topical application of 750 µg of DEET per nymph produced a mortality rate between 0% (24 h after application) and 40% (7 d later). The same dose of IR3535 produced no mortality during the same period of time. Simultaneous treatment with piperonylbutoxide (a mixed function microsomal oxidase inhibitor) synergized the lethal effect of DEET. Only DEET increased locomotor activity in nymphs exposed to a treated surface. Nymph antennectomy abolished DEET repellency but not its effect on locomotor activity. The concentrations of both these compounds required to produce either behavioral or toxicological effects are too high to have any practical applications in the control of R. prolixus.

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina

Abstract:

The effect on locomotor activity, the repellency, and the knock-down produced by 10 monoterpene alcohols were evaluated on first-instar nymphs of Rhodnius prolixus and Triatoma infestans, vectors of Chagas disease. A video tracking technique was used to evaluate locomotor activity and repellency by exposure to papers impregnated with monoterpenes. Eugenol on R. prolixus and (S)-cis-verbenol on T. infestans did not modify the locomotor activity. The remaining monoterpenes produced hyperactivity on both species, although the concentration required was at least a 1,000 times higher than that of deltamethrin (positive control). Carvacrol, eugenol, and geraniol resulted as repellent as N,N-diethyl-m-toluamide (positive control) for both species. A similar result was observed for almost every monoterpene on T. infestans. Knock-down effect was evaluated by exposing the nymphs in closed recipients. The order of increasing toxicity on R. prolixus was (KT50 values in min): geraniol (213.7) < α-terpineol (164.5) < linalool (124.2) < carvacrol (111.6) < eugenol (89.8) < thymol (78.9), and on T. infestans: α-terpineol (289.8) < eugenol (221.3) < carvacrol (164.2) < linalool (154.9) < thymol (96.7). All monoterpenes were less toxic than the positive control, dichlorvos (3.6 min for R. prolixus and 3.9 min for T. infestans). After 7 h of exposure, (-)-carveol, citronellol, and menthol (on both species) and geraniol (on T. infestans) produced <50% of knock-down. After these results, it is worthwhile to explore more deeply the potential of these compounds as tools for controlling Chagas disease vectors.

Author affiliation: Moretti, Ariadna Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina

Author affiliation: Zerba, Eduardo Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentina

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentina

Abstract:

Certain monoterpenes produced by aromatic plants are known to have lethal and sublethal effects on insects. As there is a need to replace conventional pesticides (organophosphates, carbamates, pyrethroids) with biorational pesticides, we evaluated the behavioural and toxicological responses of the German cockroach, Blattella germanica, exposed to the following monoterpenes, namely (+)-α-pinene, (-)-α-pinene, limonene, menthone, linalool, menthyl acetate and geraniol. Locomotor activity and repellency were quantified using avideo tracking system. To study the effect on locomotor activity, larvae were exposed to filter papers treated with concentrations of monoterpenes ranging between 1.4 and 1,400 μg/cm2. Only menthyl acetate applied at a concentration of 14 μg/cm2 or higher increased the locomotor activity of the larvae. Repellency was evaluated by exposing larvae to circles of filter paper divided in two equal zones: one zone was treated with a solution of a monoterpene in acetone (14 or 140 μg/cm2) and the other with only acetone. Larvae were repelled by all the monoterpenes tested. The two concentrations of geraniol and the highestconcentration of menthyl acetate and linalool were as repellent as DEET (positive control). The fumigant effect was evaluated by exposing larvae to vapour from 100 μl of pure monoterpene in a sealed container. The values of the 50% Knock-down Times (KT50), expressed in minutes, were: (+)-α-pinene: 11.8, (-)-α-pinene: 14.6, limonene: 81.0, menthone: 141.0, and linalool: 238.6. (+)-α- Pinene was as good a fumigant as dichlorvos (positive control, KT50 = 9.7 min). The least effective compounds were menthyl acetate and geraniol (both affected less than 50% of larvae after 490 min of exposure). In conclusion, (+)-α-pinene (for its fumigant effect), menthyl acetate (for its hyperactivant effect) and menthone and geraniol (for their repellent properties) could potentially be used for controlling B. germanica.

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Universidad Nacional de San Martín; Argentina

Author affiliation: Sfara, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Universidad Nacional de San Martín; Argentina

Author affiliation: Moretti, Ariadna Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina

Author affiliation: Zerba, Eduardo Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Universidad Nacional de San Martín; Argentina

Abstract:

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 [μg each). Fifth instar nymphs were also attracted to 4-methylquinazoline alone (50 μg) but females were only attracted by the mixture of both methyl quinazolines (50 μg each). Syntheses of both methyl quinazolines were carried out starting from 2-aminoacetophenone by modifying the conditions of reported procedures.

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Universidad Nacional de San Martín; Argentina

Author affiliation: Fontán, A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina

Author affiliation: Camps, F.. Consejo Superior de Investigaciones Científicas; España

Author affiliation: Masuh, Hector Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Universidad Nacional de San Martín; Argentina

Author affiliation: Santo Orihuela, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina

Author affiliation: Fernández, D.. Consejo Superior de Investigaciones Científicas; España

Author affiliation: Cork, A.. University Of Greenwich; Reino Unido

Author affiliation: Zerba, Eduardo Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Universidad Nacional de San Martín; Argentina

Abstract:

Se evaluaron los síntomas de intoxicación con deltametrina y cis-permetrina en ninfas III de T. infestans. Se estimaron los TE 50s de distintas dosis para dos efectos: (a) incoordinación, y (b) parálisis total. Deltametrina fue tanto o más rápida en producir el primer efecto (según la dosis), cis-permetrina fue más rápida en producir el segundo. No hubo diferencia significativa entre las DE 50 a diferentes tiempos de los dos piretroides, y las ninfas tratadas con cualquiera de ellos mostraron una importante recuperación en función del tiempo. La recuperación fue inhibida cuando se aplicó simultáneamente butóxido de piperonilo. Se estudió la influencia de distintas variables sobre la toxicidad de deltametrina y cis-permetrina. La temperatura tuvo un efecto importante sobre las CE 50s y DE 50s de los piretroides estudiados. En general la toxicidad aumentó al disminuir la temperatura; pero hubo excepciones que dependieron del insecticida, el estadio ninfal y el rango de temperatura. El efecto de la temperatura sobre los TE 50s fue poco importante. En general la velocidad de acción aumentó al disminuir la temperatura; pero hubo excepciones que dependieron del insecticida, el estadio ninfal y el rango de temperatura. En experimentos con ninfas de distintas edades y estados alimentarios, resultaron más sensibles los individuos de 1 día de edad, y más tolerantes los alimentados 7 días antes. La aplicación tópica en el tórax produjo síntomas de intoxicación más rápidamente que la aplicación tópica en el extremo abdominal. Deltametrina actuó más rápidamente que cis-permetrina en un amplio rango de dosis (2-1.000 ng/insecto). En ninfas I, el isómero cis de la permetrina fue más tóxico que el isómero trans a 26 y 36°C, e igual de tóxico a 16°C. El pretratamiento con butóxido de piperonilo sinergizó la toxicidad de cis-permetrina pero no la de trans-permetrina. El pretratamiento con trifenilfosfato tuvo el efecto opuesto. La mezcla de los dos isómeros produjo un efecto de aditividad (ausencia de interacción). En ninfas III, el isómero cis de la permetrina fue más tóxico que el isómero trans a 16 y 26°C, e igual de tóxico a 36°C. Los pretratamientos con butóxido de piperonilo o trifenilfosfato no modificaron las DE 50s. La mezcla de los dos isómeros produjo un efecto de antagonismo. Ambos piretroides produjeron hiperactividad locomotora en ninfas III. Este efecto estuvo influenciado por el modo y el lugar de aplicación de los insecticidas. La hiperactividad fue inhibida por el pretratamiento con N-etilmaleimida y por el descenso de la temperatura. Ninguno de los dos insecticidas tuvo efectos subletales sobre la ingesta y la mortalidad de ninfas I y III, y sólo deltametrina produjo una disminución en la cantidad de ninfas I mudadas.

Symptoms of poisoning by deltamethrin and cis-permethrin in third instars of T. infestans were described. The ET 50s for two effects, (a) incoordination, and (b) total paralysis were calculated. Deltamethrin was equal or more rapid to produce the onset of the first effect (according the dose), and cis-permethrin to produce the onset of the second one. There was not significant differences between DE 50s at different times for the two pyrethroids. They showed equivalent initial knockdown performance, but instars recovery was observed. The synergist piperonyl butoxide inhibited recovery. The toxicities of deltamethrin and cis-permetrhrin at different intrinsec and extrinsec conditions were compared. After treatment temperature had an important effect on ED 50s of both pyrethroids, which tended to decrease when temperature decreased (but excepts depending of the insecticide, the instar, and the temperature range were observed). A low influence of temperature on ET 50s was observed. At all temperatures assayed deltamethrin was faster than cis-permethrin to produce symptoms of poisoning. The symptoms rapidly desappeared when instars intoxicated were moved from 16 to 28°C. Instars exposed to low doses of pyrethroids at 28°C, which did not show symptoms of poisoning, were rapidly affected when they were moved to 16°C. The toxicity of both pyrethroids was affected by the age and the nutritional estate of the instars. Topical application on the thorax was faster to produce the onset of incoordination than on the abdomen. The toxicity of pure and mixed cis- and trans-permethrin was evaluated. The cis isomer was more active than the trans one in both first and third instars. When the two isomers were simultaneously applied an additive effect (lack of interaction) was observed in first instars, while an antagonistic effect in third instars occured. In first instars, the toxicity of cis-permethrin was increased by piperonyl butoxide; and the toxicity of trans-permethrin was increased by triphenyl phosphate. In third instars, the toxicity of both isomers was not modified by neither piperonyl butoxide nor triphenyl phosphate. Deltamethrin and cis-permethrin caused an increase in the locomotor activity of third instars. This effect was inhibited by a temperature decrease, and by N-ethylmaleimide pretreatment. Sublethal effects on blood meal ingestion and moulting were evaluated in both first and third instars. Only deltamethrin yielded a substantial decrease in the number of moulted nymphs.

Author affiliation: Alzogaray, Raúl A.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Abstract:

The German cockroach, Blattella germanica (L.) (Blattodea: Blattellidae), is a serious worldwide pest with a considerable economical and sanitary impact. It is mainly controlled by the application of synthetic insecticides, but repeated use of these substances has promoted the appearance of resistance in cockroach populations throughout the world. The aim of this study was to compare the behavior of deltamethrin-susceptible (CIPEIN colony) and deltamethrin-resistant (JUBA and VGBA colonies) first instar nymphs exposed to the repellents N,N-diethyl-3-methylbenzamide (DEET) and ethyl 3-[acetyl(butyl)amino]propanoate (IR3535). Firstly, the behavior of the nymphs was assessed in an experimental arena in the absence of repellents. The parameters Distance Traveled, Velocity, Mobility Time, and Time Spent (in each half of the arena) were quantified using an image analyser, and showed that the behavior elicited by the three colonies was similar. After this, the behavior of the nymphs was quantified in an arena, half of which had been treated with repellent. The repellency of DEET increased as a linear function of log concentration for the three colonies. DEET elicited repellency as from a concentration of 97.49 ?g/cm2 for the CIPEIN and JUBA colonies and 194.98 ?g/cm2 for the VGBA colony. The repellency of IR3535 was weaker and started at a concentration of 389.96 ?g/cm2 for the CIPEIN colony, 779.92 ?g/cm2 for JUBA, and 1559.84 ?g/cm2 for VGBA. Finally, nymphs were exposed to 3:1, 1:1, and 1:3 DEET:IR3535 mixtures, and a synergistic effect was observed only in the CIPEIN colony.

Author affiliation: Mengoni, Sofia Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina

Abstract:

The control program of codling moth (Cydia pomonella L.) in the Río Negro and Neuquén Valley is intended to neonate larvae. However, adults may be subjected to sublethal pesticide concentrations generating stress which might enhance both mutation rates and activity of the detoxification system. This study assessed the exposure effects of chlorpyrifos on target enzyme and, both detoxifying and antioxidant systems of surviving adults from both a laboratory susceptible strain (LSS) and a field population (FP). The results showed that the FP was as susceptible to chlorpyrifos as the LSS and, both exhibited a similar chlorpyrifos-inhibitory concentration 50 (IC50) of acetylcholinesterase (AChE). The FP displayed higher carboxylesterase (CarE) and 7-ethoxycoumarine O-deethylase (ECOD) activities than LSS. Both LSS and FP showed an increase on CarE activity after the exposure to low-chlorpyrifos concentrations, followed by enzyme inhibition at higher concentrations. There were no significant differences neither in the activities of glutathione S-transferases (GST), catalase (CAT) and superoxide dismutase (SOD) nor in the reduced glutathione (GSH) content between LSS and FP. Moreover, these enzymes were unaffected by chlorpyrifos. In conclusion, control adults from the FP exhibited higher CarE and ECOD activities than control adults from the LSS. AChE and CarE activities were the most affected by chlorpyrifos. Control strategies used for C. pomonella, such as rotations of insecticides with different modes of action, will probably delay the evolution of insecticide resistance in FPs from the study area.

Author affiliation: Parra Morales, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente | Universidad Nacional del Comahue. Facultad de Ciencias Agrarias. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente; Argentina

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentina

Author affiliation: Cichón, Liliana Isabel. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria Alto Valle; Argentina

Author affiliation: Garrido, Silvina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria Alto Valle; Argentina

Author affiliation: Soleño, Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente | Universidad Nacional del Comahue. Facultad de Ciencias Agrarias. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente; Argentina

Author affiliation: Montagna, Cristina Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente | Universidad Nacional del Comahue. Facultad de Ciencias Agrarias. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente; Argentina

Abstract:

The control program of codling moth (Cydia pomonella L.) in the Río Negro and Neuquén Valley is intended to neonate larvae. However, adults may be subjected to sublethal pesticide concentrations generating stress which might enhance both mutation rates and activity of the detoxification system. This study assessed the exposure effects of chlorpyrifos on target enzyme and, both detoxifying and antioxidant systems of surviving adults from both a laboratory susceptible strain (LSS) and a field population (FP). The results showed that the FP was as susceptible to chlorpyrifos as the LSS and, both exhibited a similar chlorpyrifos‐inhibitory concentration 50 (IC50) of acetylcholinesterase (AChE). The FP displayed higher carboxylesterase (CarE) and 7‐ethoxycoumarine O‐deethylase (ECOD) activities than LSS. Both LSS and FP showed an increase on CarE activity after the exposure to low‐chlorpyrifos concentrations, followed by enzyme inhibition at higher concentrations. There were no significant differences neither in the activities of glutathione S‐transferases (GST), catalase (CAT) and superoxide dismutase (SOD) nor in the reduced glutathione (GSH) content between LSS and FP. Moreover, these enzymes were unaffected by chlorpyrifos. In conclusion, control adults from the FP exhibited higher CarE and ECOD activities than control adults from the LSS. AChE and CarE activities were the most affected by chlorpyrifos. Control strategies used for C. pomonella, such as rotations of insecticides with different modes of action, will probably delay the evolution of insecticide resistance in FPs from the study area.

EEA Alto Valle

Author affiliation: Parra Morales, Laura Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente | Universidad Nacional del Comahue. Facultad de Ciencias Agrarias. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente; Argentina

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental; Argentina

Author affiliation: Cichon, Liliana. INTA. Estación Experimental Agropecuaria Alto Valle; Argentina

Author affiliation: Garrido, Silvina Alejandra. INTA. Estación Experimental Agropecuaria Alto Valle; Argentina

Author affiliation: Soleño, Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente | Universidad Nacional del Comahue. Facultad de Ciencias Agrarias. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente; Argentina

Author affiliation: Montagna, Cristina Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente | Universidad Nacional del Comahue. Facultad de Ciencias Agrarias. Centro de Investigaciones en Toxicología Ambiental y Agrobiotecnología del Comahue. Laboratorio de Investigaciones Bioquímicas y Químicas del Ambiente; Argentina

Abstract:

Soybean is the most important crop in Argentina and Rachiplusia nu (Gueneé) (Lepidoptera: Noctuidae) is one of its main pests. In this study, the toxicity of five pyrethroids applied topically and by exposure to films on filter paper was evaluated on third instar larvae from a laboratory strain and a field population of R. nu. Four cyanopyrethroids and one noncyanopyrethroid (permethrin) were tested. All cyanopyrethroids showed the same order of increasing toxicity, regardless of the form of application and origin of the larvae: cypermethrin < lambda-cyhalothrin < deltamethrin < beta-cyfluthrin. Knock down Dose 50% and Knock down Time 50% values increased as a function of the solubility of cyanopyrethroids in water. Permethrin showed a different behavior: it was the most toxic insecticide for the laboratory strain when applied topically, but the least toxic when larvae were exposed to filter papers. In general, the pyrethroids were more toxic for laboratory larvae than for the field ones. After calculating Resistance Factor (RF) values, low-moderate resistance to permethrin, cypermethrin and lambda-cyhalothrin was observed in the experiments with topical application. However, exposure to films on filter papers failed to detect resistance. There was not correlation between the RF values obtained by both methods. These results suggest that the population of studied here has low-moderate resistance to some pyrethroids, and that topical application is a more appropriate method for quantifying resistance than exposure to insecticide films on filter paper.

La soja es el cultivo más importante en la República Argentina y Rachiplusia nu (Gueneé) (Lepidoptera: Noctuidae), una de sus principales plagas. En este estudio se evaluó la toxicidad de cuatro cianopiretroides y un no-cianopiretroide, aplicados en forma tópica o por exposición a filmes sobre papeles de filtro, en ninfas del tercer estadio de una cepa de laboratorio y una población de campo de R. nu. Todos los cianopiretroides mostraron el mismo orden de toxicidad creciente, independientemente de la forma de aplicación y del origen de las larvas: cipermetrina < ?-cihalotrina < deltametrina < ß-ciflutrina. Los valores de Dosis de Volteo para el 50% (DV50) y de Tiempo de Volteo para el 50% (TV50) aumentaron en función de la solubilidad de los cianopiretroides en agua. El no-cianopiretroide permetrina mostró un comportamiento diferente: fue el insecticida más tóxico para la cepa de laboratorio cuando se hizo una aplicación tópica, pero el menos tóxico cuando las larvas fueron expuestas a filmes sobre papeles de filtro. En general, todos los piretroides fueron más tóxicos para las larvas criadas en laboratorio que para las provenientes del campo. La estimación de los valores de Factor de Resistencia (FR) permitió establecer que la población de campo presentaba resistencia moderada o baja a permetrina, cipermetrina y ?-cihalotrina, cuando los insecticidas fueron aplicados en forma tópica. Sin embargo, no se detectó resistencia cuando se realizó la exposición en papeles de filtro tratados. No hubo correlación entre los valores de FR obtenidos por ambos métodos. Estos resultados sugieren que la población de campo de R. nu estudiada, presentaba resistencia moderada a algunos piretroides, y que la aplicación tópica es un método más apropiado que la exposición a filmes sobre papeles de filtro para cuantificar la resistencia.

Author affiliation: Russo, Romina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Santa Fe. Estación Experimental Agropecuaria Oliveros; Argentina

Author affiliation: Gamundi, Juan C. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación de Plagas e Insecticidas; Argentina

Author affiliation: Alzogaray, Raúl Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín; Argentina