Effect of pest management systems on ground-dwelling spider assemblages in an apple orchard in Hungary

Ground-dwelling spider assemblages in differently treated plots of a Hungarian apple orchard were investigated by pitfall trapping. The samples were taken weekly from April to November over three years as part of a study to compare the effects of integrated pest management based on selective insecticides, with conventional control utilising broad-spectrum compounds. Attention was also paid to the effects of boundaries and of different weed patterns on the spider assemblages. No significant differences were found between the conventional and IPM plots in species richness and composition, density and diversity of epigeic spider communities. The density in the IPM plots was moderately higher in only one year. Greater spider densities were observed in the tree rows where the weed coverage was higher than in the alleys where mechanical weed control was applied. However, community structures did not differ significantly. Near the edge of the orchard, the density and species richness of epigeic spiders were higher and the community structure differed slightly from that of the orchard habitats. The spiders showed one population peak in springtime in all habitats, but this was more extended in the edge. The collections included 1147 individuals representing 37 species, with Xysticus kochi, Pardosa agrestis and Titanoeca schineri being the most dominant species. Their population dynamics, sex ratio and habitat preferences are also discussed. (C) 1999 Elsevier Science B.V. All rights reserved.