Selectividad de insecticidas utilizados en cultivos hortícolas del Cinturón Hortícola Platense sobre el depredador Eriopis connexa en el marco del Manejo Integrado de Plagas

El objetivo principal de esta tesis fue la evaluación de la toxicidad de los insecticidas comúnmente utilizados en cultivos hortícolas sobre el depredador generalista Eriopis connexa (Germar, 1824) (Coleoptera: Cochinellidae) con la finalidad de conocer el perfil toxicológico de los mismos y determinar la selectividad de los mismos hacia este organismo no blanco. La evaluación se realizó mediante ensayos de toxicidad aguda en laboratorio considerando los efectos letales y subletales seleccionados sobre los parámetros vitales del depredador, principalmente aquellos relacionados con su desempeño como agente de control biológico. En el caso de los adultos de E. connexa, se evaluó la toxicidad crónica. Se estudió la susceptibilidad de los diferentes estados de desarrollo del depredador hacia los diferentes productos, a través de distintas vías de exposición. Sobre la base de los resultados de éstos estudios será posible identificar los insecticidas más selectivos y ambientalmente amigables, para ser empleados en combinación con E. connexa, uno de los principales enemigos naturales de las plagas de los cultivos hortícolas del CHP. Los resultados de estos estudios servirán a futuro como base para rediseñar estrategias de control de bajo impacto ambiental en el marco del Manejo Integrado de Plagas (MIP).Facultad de Ciencias Exacta

Comparative susceptibility of two Neotropical predators, Eriopis connexa and Chrysoperla externa, to acetamiprid and pyriproxyfen: short and long-term effects after egg exposure

Compatibility assessments between selective insecticides and the natural enemies of pests are essential for integrated-pest-management programs. Chrysoperla externa and Eriopis connexa are two principal Neotropical predators of agricultural pests whose conservation in agroecosystems requires a toxicity evaluation of pesticides to minimize the impact on those beneficial insects on the environment. The objective of this work was to evaluate the toxicity of the insecticides pyriproxyfen and acetamiprid on C. externa and E. connexa eggs exposed to the maximum recommended field concentrations of each along with three successive dilutions. The survival and the immature developmental time were assessed daily until adulthood and the mean survival time calculated over a 10-day period. The cumulative survival of E. connexa was reduced at all concentrations of both insecticides, while that of C. externa was significantly decreased by ≥50 mg L-1 of acetamiprid and ≥37.6 mg L-1 of pyriproxyfen. In both species, the reductions occurred principally on the eggs and first larval instar. Survival curves, in general, differed from those of the controls, with the mean survival time of E. connexa being significantly shorter in insecticides treatments than that of the controls. Certain concentrations of each of the insecticide lengthened the egg and first-larval-instar developmental periods of E. connexa and C. externa, respectively. Also, pyriproxyfen reduced the first-larval-instar period and lengthened the fourth of E. connexa. Acetamiprid was more toxic to E. connexa than to C. externa at the two highest concentrations. Conversely, at those same concentrations of pyriproxyfen, the relative toxicity to the two species was reversed. The present work represents the first investigation on the comparative susceptibility of two relevant Neotropical biological control agents to acetamiprid and pyriproxyfen. Also, it highlights the necessity of assessing long-term effects in the compatibility studies between natural enemies of agricultural pests and insecticides.Centro de Investigaciones del MedioambienteCentro de Estudios Parasitológicos y de Vectore

Efectos indirectos de insecticidas convencionales y biorracionales sobre la alimentación de Rachiplusia nu (Lepidoptera: Noctuidae)

La evaluación conjunta de los efectos letales y subletales de insecticidas sobre plagas, permite alcanzar un mejor conocimiento de su eficacia de acción. En este sentido, la alteración de los patrones de consumo foliar de una plaga, es un importante punto final para analizar la efectividad de insecticidas sobre insectos fitófagos. Los insecticidas que interfieren con el normal comportamiento alimentario de un insecto plaga contribuyen en el manejo de su población. El objetivo del presente estudio fue evaluar el efecto del endosulfán, cipermetrina, spinosad y metoxifenocida sobre el comportamiento alimentario de Rachiplusia nu, plaga potencial de varios cultivos, en especial soya, a través de experimentos de elección en laboratorio (Centro de Investigaciones del Medio Ambiente (CIMA) La Plata, Argentina). Además, se evaluó la supervivencia de las larvas expuestas a dichos productos. La cipermetrina y el spinosad indujeron efectos antialimentarios sobre las larvas tratadas. El endosulfán no causó efectos significativos sobre este punto final, mientras que las larvas expuestas a metoxifenocida mostraron preferencia por las hojas tratadas. Los insecticidas biorracionales ocasionaron mayor mortalidad sobre R. nu que los convencionales. Estos resultados aportan conocimientos básicos para redefinir estrategias de control.The assessment of sublethal and lethal effects of insecticides on pests allows obtaining further insight of their efficacy. In this way, the pest feeding pattern is a relevant toxicological endpoint to analyze the effectiveness of insecticides on phytophagous insects, due to insecticides that interfere with the normal feeding behavior of a pest contributing to its population management. The objective of the present study was evaluating the effects of endosulfan, cypermethrin, spinosad and methoxyfenozide on feeding pattern of Rachiplusia nu, a potential pest in several crops but mainly in soybean, using laboratory choice test (Centro de Investigaciones del Medio Ambiente (CIMA) La Plata, Argentina). Additionally, the larval survival was also assessed. Cypermethrin and spinosad induced antifeedant effects on exposed larvae. Endosulfan did not cause significant effects, while larvae exposed to methoxyfenozide showed preference towards the treated leaves. Biorational insecticides showed higher mortality to R. nu control than conventional ones. These new insights contribute with knowledge for redefining effective pest control strategies.Fil: Rimoldi, Federico. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Departamento de Química. Centro de Investigaciones del Medio Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fogel, Marilina Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores (i); ArgentinaFil: Schneider, Marcela Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores (i); ArgentinaFil: Ronco, Alicia Estela. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Departamento de Química. Centro de Investigaciones del Medio Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Interactions between the entomopathogenic fungus <i>Beauveria bassiana</i> and the Neotropical predator <i>Eriopis connexa</i> (Coleoptera: Coccinellidae): Implications in biological control of pest

Aphids (Hemiptera: Aphididae) are serious pests of crops causing direct damage by feeding and indirect by the transmission of plant viruses. The use of conventional insecticides for controlling aphids has caused different problems and insecticide resistance. Accordingly, there is more interest in alternative control methods such as biological control by natural enemies for sustainable agricultural management. Among biological control agents, entomopathogenic fungi are one of the most significant microbial pathogens of insects. Also, Coccinellidae, as a major group, is a serious natural enemy. Both larval and adult stages of Coccinellidae feed on different soft-body pests, such as aphids. Eriopis connexa (Germar) (Coleoptera: Coccinellidae) is a common species in agroecosystems of the Neotropical region where it is considered to be a potential control agent. Pathogens and arthropod natural enemies may contribute to the control of phytophagous pests; however, it is important to assess potential interactions within biological control agents that share hosts (intraguild interaction) to evaluate their combined use for pest control. Therefore, the aim of this study was to evaluate the compatibility and interaction (lethal and sublethal effects) between E. connexa and the entomopathogenic fungus Beauveria bassiana (Bals.-Criv.) Vuill. (Ascomycota: Hypocreales). Both are important biological control agents of aphids. The pathogenicity of B. bassiana against larvae, pupae and adults of the predator E. connexa was evaluated, and results showed, that B. bassiana infected the coleopteran. On the other hand, interaction between B. bassiana and the predator was evaluated through infected-prey. The effects of fungus on larvae survival were significantly different when we analyzed the accumulated survival (from first larval instar to adulthood). The daily fecundity was significantly reduced at five days compared to control group. By contrast, no significant differences were observed between the five oviposition days in the rate of hatched eggs. This study shows that despite having received a single dose of the fungus in its life cycle, the population parameters of the predator E. connexa are affected. More studies would be necessary to help identify interactions between microbes and natural enemies to increase and enhance opportunities and further develop biological pest control programs.Facultad de Ciencias Naturales y Muse

Evaluación del gasterópodo sudamericano Heleobia parchappii como organismo diagnóstico en bioensayos de toxicidad con cadmio

Gastropods are abundant key components in freshwater ecosystems, many of which are affected by anthropogenic activities. The genus Heleobia is widely distributed across Argentina, and the native Heleobia parchappii is very common in the Pampean Region. The identification of native candidate species for toxicity testing is gaining increasing interest. The objectives of the present study were to evaluate 1) the susceptibility of H. parchappii to a reference toxicant (Cl₂ Cd), and 2) its suitability for toxicity testing by estimating LC50. Also, we discussed the applicability of the proposed protocol. Snail sensitivity was assessed by exposure to concentrations between 0.5 and 12 mg Cd/L under acute static conditions during 72 h (exposure period). Then, snails were transferred to the control medium for 24 h (post-exposure period) and checked for recovery and those not responding to stimulation were considered to be dead. The endpoints were snail immobilization (recorded every 24 h during the exposure period) and mortality at the end of the post-exposure period. Snail sensitivity was analyzed with a generalized linear mixed model (GLMM) and LC₅₀ (lethal concentration 50%) was calculated using probit analysis. Results indicated that the number of immobilized snails increased with increasing concentration. The toxic effect of Cd on snails persisted 24 h after exposure. The LC₅₀ was 2.145 (1.675-2.641) mg Cd/L. The sensitivity of H. parchappii was similar to that reported for other freshwater standard species, supporting its suitability as test organism. The protocol was appropriate for use in toxicity testing as it is simple, inexpensive and reproducible.Los gasterópodos son componentes clave de los ecosistemas acuáticos, y muchos de ellos están afectados por la actividad antrópica. El género Heleobia está ampliamente distribuido en la Argentina, y la especie nativa Heleobia parchappii es muy común en la Región Pampeana. Actualmente, existe un interés creciente en identificar especies nativas para usarlas en evaluaciones de toxicidad. Los objetivos de este estudio fueron evaluar 1) la susceptibilidad de H. parchappii a un tóxico de referencia (Cl₂ Cd), y 2) su idoneidad para ser utilizada en evaluaciones de toxicidad estimando la concentración letal 50% (CL₅₀). Además, discutimos la aplicabilidad del protocolo propuesto. La sensibilidad de los caracoles fue evaluada al exponerlos a concentraciones entre 0.5 y 12 mg Cd/L en un ensayo agudo bajo condiciones estáticas durante 72 h (tiempo de exposición). Los caracoles se transfirieron a un medio control durante 24 h (período de post-exposición) y se controló su estado para determinar si se recuperaban; aquellos que no respondían a los estímulos se consideraron muertos. Los puntos finales evaluados fueron la inmovilización de los caracoles (registrada cada 24 h durante el período de exposición) y la mortalidad al finalizar el período de post-exposición. La sensibilidad de los caracoles se analizó utilizando un modelo lineal generalizado y se calculó la CL₅₀ usando el análisis probit. Los resultados indican que el número de caracoles inmovilizados aumentó con el incremento de la concentración. El efecto tóxico del Cd sobre los caracoles persistió 24 h tras la exposición. La CL50 tuvo un valor de 2.145 (1.675-2.641) mg Cd/L. La sensibilidad de H. parchappii fue similar a la informada para otros especies estándar dulceacuícolas, lo que respalda su idoneidad como organismo de evaluación. El protocolo fue apropiado para su uso en evaluaciones de toxicidad ya que es simple, económico y reproducible.Centro de Estudios Parasitológicos y de Vectore

Efectos indirectos de insecticidas convencionales y biorracionales sobre la alimentación de Rachiplusia nu (Lepidoptera: Noctuidae)

La evaluación conjunta de los efectos letales y subletales de insecticidas sobre plagas, permite alcanzar un mejor conocimiento de su eficacia de acción. En este sentido, la alteración de los patrones de consumo foliar de una plaga, es un importante punto final para analizar la efectividad de insecticidas sobre insectos fitófagos. Los insecticidas que interfieren con el normal comportamiento alimentario de un insecto plaga contribuyen en el manejo de su población. El objetivo del presente estudio fue evaluar el efecto del endosulfán, cipermetrina, spinosad y metoxifenocida sobre el comportamiento alimentario de Rachiplusia nu, plaga potencial de varios cultivos, en especial soya, a través de experimentos de elección en laboratorio (Centro de Investigaciones del Medio Ambiente (CIMA) La Plata, Argentina). Además, se evaluó la supervivencia de las larvas expuestas a dichos productos. La cipermetrina y el spinosad indujeron efectos antialimentarios sobre las larvas tratadas. El endosulfán no causó efectos significativos sobre este punto final, mientras que las larvas expuestas a metoxifenocida mostraron preferencia por las hojas tratadas. Los insecticidas biorracionales ocasionaron mayor mortalidad sobre R. nu que los convencionales. Estos resultados aportan conocimientos básicos para redefinir estrategias de control.The assessment of sublethal and lethal effects of insecticides on pests allows obtaining further insight of their efficacy. In this way, the pest feeding pattern is a relevant toxicological endpoint to analyze the effectiveness of insecticides on phytophagous insects, due to insecticides that interfere with the normal feeding behavior of a pest contributing to its population management. The objective of the present study was evaluating the effects of endosulfan, cypermethrin, spinosad and methoxyfenozide on feeding pattern of Rachiplusia nu, a potential pest in several crops but mainly in soybean, using laboratory choice test (Centro de Investigaciones del Medio Ambiente (CIMA) La Plata, Argentina). Additionally, the larval survival was also assessed. Cypermethrin and spinosad induced antifeedant effects on exposed larvae. Endosulfan did not cause significant effects, while larvae exposed to methoxyfenozide showed preference towards the treated leaves. Biorational insecticides showed higher mortality to R. nu control than conventional ones. These new insights contribute with knowledge for redefining effective pest control strategies.Fil: Rimoldi, Federico. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Departamento de Química. Centro de Investigaciones del Medio Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fogel, Marilina Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores (i); ArgentinaFil: Schneider, Marcela Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Estudios Parasitológicos y de Vectores (i); ArgentinaFil: Ronco, Alicia Estela. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Departamento de Química. Centro de Investigaciones del Medio Ambiente; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Toxicity assessment of four insecticides with different modes of action on pupae and adults of Eriopis connexa (Coleoptera: Coccinellidae), a relevant predator of the Neotropical Region

Pesticides can be toxic to nontarget organisms including the natural enemies of agricultural pests, thus reducing the biodiversity of agroecosystems. The lethal and sublethal effects of four insecticides with different modes of action— pyriproxyfen, teflubenzuron, acetamiprid, and cypermethrin— were evaluated on pupae and adults of Eriopis connexa, an effective predator in horticultural crops. Pupal survival was reduced by pyriproxyfen (26 %) and cypermethrin (41 %). Malformations in adults emerged from treated pupae were observed after acetamiprid (82.7 and 100 % for 100 and 200 mg a.i./l, respectively), pyriproxyfen (48.6 %), and cypermethrin (13.3 %) treatments. A longer mean oviposition time was also observed in adults emerged from pupae treated with cypermethrin. Moreover, the latter insecticide as well as teflubenzuron did not reduce reproductive parameters, whereas females emerged from pyriproxyfen-treated pupae were not be able to lay eggs even when females showed large abdomens. Upon exposure of adults, survival was reduced to approximately 90 % by acetamiprid, but no reduction occurred with pyriproxyfen, teflubenzuron, or cypermethrin though the fecundity at fifth oviposition time of the female survivors was reduced. Pyriproxyfen decreased the hatching at all the oviposition times tested, whereas fertility was reduced in the fourth and fifth ovipositions by teflubenzuron and in the first and third ovipositions by cypermethrin. In conclusion, all four insecticides tested exhibited lethal or sublethal effects, or both, on E. connexa. The neurotoxic insecticides were more harmful than the insect-growth regulators, and pupae were more susceptible than adults. The toxicity of insecticides on the conservation of predators in agroecosystems of the Neotropical Region is discussed.Centro de Estudios Parasitológicos y de VectoresCentro de Investigaciones del Medioambient

Impact of the neonicotinoid acetamiprid on immature stages of the predator <i>Eriopis connexa</i> (Coleoptera: Coccinellidae)

Eriopis connexa is a native coccinelid predator in the Neotropical Region. In Argentina it is commonly found associated to sucking pests in several crops and among them aphids and whiteflies. These pests are usually controlled with newly developed systemic insecticides, such as the neonicotinoids. However, the compatibility between selective pesticides and natural enemies is required before incorporating them in integrated pest management (IPM) packages. Within this frame, the objective of this study was to evaluate the side effect of various concentrations/doses of one commonly used neonicotinoid in vegetal crops, acetamiprid, on immature stages of E. connexa by dipping or topical exposure for eggs and larvae, respectively. Acetamiprid reduced egg hatching from 34 to 100 %. Moreover, the embryogenesis was disrupted by insecticide at early embryo stage at all tested concentrations. Second larval instar was more susceptible to acetamiprid than the fourth one and this susceptibility was positively related with the tested concentrations. On the other hand, the survival reduction at larval stage reached 100 % from 20 mg a.i./L (10 % of maximum field concentration). Besides, the reproduction of the females developed from topical bioassays on fourth instar larvae was strongly affected, with reduction in fecundity and fertility from 22 to 44 % and from 37 to 45 %, respectively. Overall the results showed a high toxicity of acetamiprid on immature stages of E. connexa, demonstrating that this broadly used insecticide could reduce biocontrol services provided by this predator and could also likely disturb IPM programs.Centro de Investigaciones del MedioambienteCentro de Estudios Parasitológicos y de Vectore

Compatibility between entomopathogenic fungi and biorational insecticides in toxicity against <i>Ronderosia bergi</i> under laboratory conditions

Our aim was to evaluate the efficacy of combinations between two biorational insecticides (luphenuron, methoxyfenozide), a new synthetic chemical pesticide (rynaxypyr), and three entomopathogenic fungi strains (Beauveria bassiana LPSc 1067, LPSc1082), and Metarhizium anisopliae (LPSc 907) in the biocontrol of the pest grasshopper Ronderosia bergi (Sta°l) under laboratory conditions. The insecticides were tested at three concentrations: the average concentration recommended for application in the field (100 %) and 50 % and finally 25 % of that level. The fungal strains used were adjusted to 1 9 108, 1 9 106, and 1 9 104 conidia ml-1. The combinations of those insecticides with B. bassiana (LPSc 1067, LPSc 1082) and M. anisopliae (LPSc 907) caused higher mortality to R. bergi nymphs than any of the individual agents used alone. The three insecticides tested did not affect the isolates of the two species of entomopathogenic fungi employed. In conclusion, the use of these biorational insecticides in an IPM program aimed at control of the grasshopper R. bergi could be of value.Facultad de Ciencias Naturales y Muse

Compatibility between entomopathogenic fungi and biorational insecticides in toxicity against <i>Ronderosia bergi</i> under laboratory conditions

Our aim was to evaluate the efficacy of combinations between two biorational insecticides (luphenuron, methoxyfenozide), a new synthetic chemical pesticide (rynaxypyr), and three entomopathogenic fungi strains (Beauveria bassiana LPSc 1067, LPSc1082), and Metarhizium anisopliae (LPSc 907) in the biocontrol of the pest grasshopper Ronderosia bergi (Sta°l) under laboratory conditions. The insecticides were tested at three concentrations: the average concentration recommended for application in the field (100 %) and 50 % and finally 25 % of that level. The fungal strains used were adjusted to 1 9 108, 1 9 106, and 1 9 104 conidia ml-1. The combinations of those insecticides with B. bassiana (LPSc 1067, LPSc 1082) and M. anisopliae (LPSc 907) caused higher mortality to R. bergi nymphs than any of the individual agents used alone. The three insecticides tested did not affect the isolates of the two species of entomopathogenic fungi employed. In conclusion, the use of these biorational insecticides in an IPM program aimed at control of the grasshopper R. bergi could be of value.Facultad de Ciencias Naturales y Muse