Spiders (Arachnida: Araneae) in organic apple (Rosaceae) orchards in southeastern France

Summary

The role of spiders (Arachnida: Araneae) in biological control programmes has received less attention than that of insect natural enemies. The aim of this two-year study was to obtain descriptive data on spider spring field population structure and dynamics. The study was carried out in one insecticide-free and four organic apple orchards in southeastern France. Rolls and bands of corrugated cardboard near the ground and shoots infested with Dysaphis plantaginea (Passerini) (Hemiptera: Aphididae) in the tree canopy were used to sample spiders. Thirty-three spider species belonging to 14 families were identified from both sampling methods. Cheiracanthium mildei Koch (Araneae: Cheiracanthiidae) was clearly the predominant arboreal spider species in aphid-infested shoots (>57%). More than half of the spiders recorded in cardboard bands belonged to three species Drassodes pubescens (Thorell) (Araneae: Gnaphosidae), Pseudeuophrys erratica (Walckenaer) (Araneae: Salticidae), and Icius hamatus (Koch) (Araneae: Salticidae). Salticidae (39.9%) and Gnaphosidae (23.4%) families dominated significantly the spider assemblages observed in the cardboard rolls and were present on almost all sampling dates. However, in the two shelter types, the spider abundance curve clearly had a poly-modal shape. This may be due to the sequential arrival of some spider species or their dominance in a certain period of our study.