Structure of the Assemblages of Spiders in Mediterranean Pear Orchards and the Effect of Intensity of Spraying

摘要

Spiders are one of the most abundant predatory arthropods in fruit tree orchards, where they contribute to pest control. The application of pesticides in these orchards has been largely reported to negatively affect spiders, lowering their abundance and diversity. In this study, we described the structure of the community of spiders in four Mediterranean pear orchards, and we assessed the effect of the intensity of spraying on the spider assemblages. Two of the orchards had low-intensity spraying of pesticides and the other two were sprayed more intensively. Spiders were generally more abundant and diverse in the orchards with low intensity of spraying. Moreover, the impact of the intensity of spraying varied depending on the family of spiders, with only some families of wandering spiders being significantly affected by the intensity of spraying. This suggests that the impact of pesticides on spider could be explained, at least in part, by their foraging mode. However, other local environmental factors apart from the intensity of spraying may have accounted for the differences in abundance and structure of the spider assemblages registered in pear orchards in the present research.