Abundance and diversity of spiders in lemon orchards with different weed management systems

Abstract

In 2002 and 2003, a study was carried out in three lemon orchards from Mafra, in the Oeste region of Portugal, aiming at study the abundance and taxonomic composition of spiders under three different weed management systems, i.e., ground cover with resident vegetation, ground cover by sowing selected plant species and herbicide application. A total of 3429 specimens were collected using two sampling techniques, i.e., suction and beating. All specimens were identified at the family and genus levels except when not possible (e.g., damaged specimens or some immature stages). The Linyphiidae and Salticidae specimens were not identified at the genus level due to inherent identification difficulties. The collected specimens were distributed among 43 genera and 17 families. The Linyphiidae was the dominant family (23%). Among the identified genera, Cheiracanthium (Miturgidae), Araneus (Araneidae), Theridula (Theridiidae), Diaea (Thomisidae), Oxyopes (Oxyopidae), Synema (Thomisidae), Clubiona (Clubionidae) and Theridion (Theridiidae) are considered potential predators of citrus pests. Web spiders were more abundant than hunting spiders in our samples. Spider captures in lemon trees were higher in both ground cover systems, in comparison with the herbicide application. The beating technique was more efficient than suction, for spider sampling, on lemon trees.