Effect of Copper Oxychloride on the Olive Infestation by Bactrocera oleae in Northeastern Portugal

Copper is an element required by all organisms, whose deficiency results in reduction in biological function and potentially death. Adequate levels of copper content in plant tissue have been linked to greater resistance to diseases or physiological disorders. In olive groves, copper-based products are likely to be the most effective options for main fungal and bacterial diseases control. Moreover this element is reported to have an important role as symbionticide, destroying bacteria associated with the olive fly, Bactrocera oleae, as well an ovipositional deterrent action, and so negatively affecting the development of the pest. In order to evaluate the effect of spraying copper oxychloride on the olive infestation by B. oleae, a study was carried out in northeastern Portugal, during 2003 and 2004. A grove with about 2 ha of surface was sprayed once each year, at the beginning of autumn, while a similar neighboring grove with the same area acted as unsprayed control. The insect flight was monitored with a network of McPhail traps and yellow sex pheromone traps. For estimating fruit infestation, samples were collected on a fortnightly basis, and were observed in the laboratory under a stereoscopic microscope. The infestation level was expressed either as total infestation or infestation with live individuals. Data were analyzed by one-way analysis of variance. Results suggest that sprays with copper oxychloride can help in reducing the infestation by the olive fly. This role may be particularly useful on organic olive groves, due to the lack of effective control measures against the pest.