Influence of site quality on the attack of Platypus mutatus Chapuis (Coleoptera, Platypodidae) to a willow plantation (Salix babylonica x Salix alba cv 131/27)

Se estudió la influencia de la calidad del sitio sobre el ataque del taladro de los forestales (Platypus mutatus Chapuis) en una plantación de Salix babylonica x Salix alba cv 131/27, y se elaboró una alternativa de manejo de la plaga de bajo impacto ambiental. En la plantación, de 14 años de edad, se diferenciaron dos rodales, uno más productivo (incremento promedio anual: 21.99 m3/ha/año) y otro menos productivo (17.39 m3/ha/año). El porcentaje de sauces atacados por Platypus mutatus fue significativamente mayor en el más productivo (41.8% vs. 22.82%). En ambos rodales los sauces infestados presentaron una circunferencia significativamente mayor a la de los que no estaban atacados por la plaga. En el rodal más productivo las plantas con un orificio activo fueron de menor circunferencia que las que tenía dos, tres y cuatro o más orificios activos. En el menos productivo no se detectaron diferencias significativas en la circunferencia de los sauces que presentaron distinto grado de ataque. Como técnica preventiva de control de Platypus mutatus se propone (1) pulverizar los fustes de árboles dominantes de sectores productivos de una plantación utilizando productos químicos de reducido impacto ambiental y (2) efectuar manejos forestales apropiados que favorezcan la supervivencia y reproducción de aves y mamíferos predadores de la plaga.The goals of this study were to examine the importance of site quality on the attack of the wood borer Platypus mutatus Chapuis to a plantation of Salix babylonica x Salix alba cv 131/27, and to provide an alternative strategy with low environmental impact to manage this pest. The study site was located in the First Section of the delta islands near the Paraná de las Palmas River (Buenos Aires Province, Argentina). The plantation (14 years old) was divided in two plots: a more productive plot (mean annual increment: 21.99/m3/ha/year, surface area: 1.27 ha), and a less productive plot (increment: 17.39/m3/ha/year, surface area: 1.06 ha). Significantly higher numbers of willow trees were attacked by Platypus mutatus in the more productive plot (41.8% vs. 22.82%). However, in both plots average circumference were greater when trees were infested with Platypus mutatus relative to those uninfested. In the more productive plot, smaller circumference sizes were detected in trees with only one active hole compared to those with two and three holes, and four or more active holes. In contrast, no significant differences were obtained in the circumferences among infested trees with one, two, three and four or more active holes in the less productive plot. Therefore, results suggest that a better way to control Platypus mutatus attack is (1) by spraying trunks of dominant and codominant trees in productive plots with insecticides of reduced environmental impact, and (2) by carrying out appropriate forest management strategies to favour survival and reproduction of bird and mammal predators