No abstract

RESUMEN -El ataque de las hormigas cortadoras es una de las principales razones de pérdida de plantas durante la etapa de establecimiento de un monte forestal. Los objetivos de este estudio fueron evaluar la intensidad de forrajeo de Acromyrmex lundi asociado a algunas condiciones ambientales y procedencias de Eucalyptus globulus y estimar el impacto de la herbivoría sobre el crecimiento inicial de estos árboles. Dos ensayos se llevaron a cabo durante dos temporadas estivo-otoñales consecutivas, en el Campo Experimental de la Universidad Nacional de Luján, Argentina. Los materiales de diferentes procedencias fueron dispuestos en bloques equidistantes a 5 m de un nido activo de A. lundi. Durante doce semanas se contabilizó el número de hojas cortadas por las hormigas y se registraron algunas variables meteorológicas. En el segundo año la mitad de las parcelas fue protegida de las hormigas y se midieron variables de crecimiento. Los materiales de todas las procedencias fueron atacadas por A. lundi, aunque el número de hojas cosechada fue significativamente diferente sólo entre los orígenes Flinders Island (52,5 hojas) y Nullo Mountain (28,5 hojas). El número de días lluviosos fue el único factor ambiental que se relacionó positivamente con la actividad de las hormigas.Todos los tratamientos redujeron significativamente la altura, el diámetro y el área foliar cuando fueron atacados por las hormigas. Las distintas procedencias compensaron diferencialemnte la herbivoría. Se discuten los resultados en función de los criterios a tener en cuenta para la selección de materiales genéticos como herramienta de manejo y control del ataque de A. lundi. Palabras

Two exotic fruit flies species, Zaprionus indianus Gupta and Drosophila suzukii (Matsumura), were detected in Argentina in recent years. In this note, the southernmost detection of Z. indianus in Argentina and an estimation of the field infestation level caused by both drosophilid species on figs (Ficus carica L.) and raspberries (Rubus idaeus L.) are reported.

No abstract

Eucalyptus trees are among the most important forest resources in Argentina. The weevils of the genus Gonipterus are specialist insects that feed on their leaves. The objectives of this work were to estimate larval consumption and to evaluate the oviposition preference of G. pulverulentus among different species of Eucalyptus. Developmental time, consumption, final weight and some nutritional indexes were evaluated from cohorts of larvae grown on five different Eucalyptus species. Ovipositional preference was evaluated by a multiple choice assay. Five couples were placed in the center of a cage, together with a branch of each Eucalyptus species. The oothecae and the eggs inside them were counted for 12 days. Larval developmental times did not differ among the Eucalyptus species tested, although differences in final weight were observed. The larvae that consumed E. maidenii almost doubled the weight of those fed on E. camaldulensis. Maximum consumption was observed on larvae feeding on E. globulus and it was significantly higher than that of larvae feeding on the E. viminalis. The efficiency of conversion of ingested food of the larvae fed with E. viminalis was significantly larger than that recorded on E. globulus and E. camaldulensis. The choice experiment shows that females had no ovipositional preference. These results indicate that E. viminalis and E. camaldulensis are the species of higher and lower nutritional quality respectively for the development of G. pulverulentus.

The bronze bug, Thaumastocoris peregrinus Carpintero & Dellapé, 2006 (Heteroptera: Thaumastocoridae) originally restricted to Australia, is an important emerging pest of Eucalyptus plantations in the Southern Hemisphere. It feeds on mature leaves, causing the loss of photosynthetic surface area and defoliation and, according to some studies, even tree death. In this work, feeding activities of T. peregrinus on Eucalyptus camaldulensis Dehn leaves and its primary food resources were identified. In cross sections of leaves, solid salivary deposits on epidermal cells and in the vicinity of stomata cells were detected. In subepidermal cells of the palisade parenchyma near the stylet penetration point, disorganization and removal of chloroplasts were also observed. The presence of chlorophyll in guts of adults and nymphs was analyzed using spectrophotometry and confocal laser scanning to obtain in situ fluorescent spectra. Both spectra showed chlorophyll absorbance peaks. In addition, the presence of chlorophyll in guts of T. peregrinus using fluorescence microscopy was identified. These results provide the first evidence that T. peregrinus feeds from the palisade parenchyma (chlorenchyma) of Eucalyptus leaves.

Drosophila suzukii Matsumura, known as spotted wing drosophila (SWD), is an Asiatic invasive fruit pest that has spread over the world in the last fifteen years, due to its high reproductive rate, its tolerance to different environmental conditions, the international fruit trade, and its wide range of host plants. In Buenos Aires, Argentina, blueberry is a major susceptible crop, although other cultivated and non-cultivated fruit species are frequent. The aim of this study was to evaluate the host suitability of commercial and non-cultivated fruit species (blueberries, plums, mulberries and cherries) at two stages of maturity by estimating an index that takes into account biological and biometric parameters. The development and survival of SWD cohorts reared on different fruits were followed from egg to adult emergence. Then, adults were sexed and some biometric traits were measured. The indices: Wing loading, Wing aspect and the Relative Performance Index (RPI) were estimated. The shortest developmental time and the maximum egg to adult survival were observed in the specimens developed in mulberry, in both stages of maturity. Only the length of the thorax showed significant differences between treatments in both sexes, and the largest adults were those reared in the ripe mulberries. The RPI, which relates performance and biometric variables, was the best parameter to evaluate the host suitability of SWD. So, it could be used as an indicator of the nutritional quality of fruits available in a region and to evaluate the importance of alternative hosts in the population dynamic of SWD.

No abstract