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

Abstract

Spiders are key predatory arthropods that are negatively affected by spraying pesticides in orchards. The aim of this research was to determine the structure of the community of spiders in pear orchards and the impact of the intensity of spraying. The study was carried out over three years in four pear orchards in southern Spain; two of them were conducted by ourselves with no or low-intensity spraying of insecticides, and two under the criteria of technicians (conventional). Spiders were sampled on pear trees by the beating method. The orchards hosted a rich community of spiders belonging to 13 different families and 51 genera. However, the genera Philodromus, Oxyopes, Cheiracanthium, Icius, and Neoscona accounted for 72% of the captures. Spiders were more abundant and had a higher richness of genera in the low-intensity spraying than in conventional orchards. Philodromidae, Salticidae, and Cheiracanthiidae experienced a significant population reduction in conventional orchards, while Araneidae, Linyphiidae, and Thomisidae were not significantly affected by the intensity of spraying. The wandering hunting mode could explain the negative impact on Philodromidae, Salticidae, and Cheiracanthiidae but does not explain the lack of effect on Oxyopidae and Thomisidae. No significant effect was found on any family of web builders.

Ants reduce fruit damage caused by psyllids in Mediterranean pear orchards

“…2,20 The control of psyllids in this region is based mainly on the use of insecticides. 2,21,24 The present research, carried out in the southwestern Mediterranean area, demonstrated that the intensification in the use of insecticides indeed produced a reduction in the populations of C. pyri and the incidence of russet. However, the abundance of psyllids and the russet impact depended on the ecological context and were much reduced in the presence of ants, as the most important predator of psyllids in this area.…”

“…Pear psyllids are currently one of the main pests of pear orchards in temperate Europe and the Mediterranean basin, and one of the principal problems occasioned by psyllid infestations is the devaluation of fruits due to russet 2,20 . The control of psyllids in this region is based mainly on the use of insecticides 2,21,24 . The present research, carried out in the southwestern Mediterranean area, demonstrated that the intensification in the use of insecticides indeed produced a reduction in the populations of C. pyri and the incidence of russet.…”

“…In the southwestern Mediterranean area, psyllids are controlled mainly by the reiterated use of abamectin and paraffinic oil, with up to five applications per growing season in conventional orchards. 21,24 According to the present research, conventional orchards in this area overuse insecticides, as no improvement in the control of psyllids seems to occur beyond the third application of insecticides. In addition, as it was predicted, spraying excessively increased the incidence of russet due to the reduction of the abundance of ants.…”

“…17 Predatory hemipterans, such as anthocorids and mirids, spiders and ants have been reported as key groups of natural enemies in pear orchards. 1,[20][21][22][23][24][25][26][27][28] However, the importance of these groups of predators for the control of pear psyllids seems to vary among regions. Anthocoris nemoralis (Fabricius) (Hemiptera: Anthocoridae) has been reported as the key species in temperate Europe.…”

“…Pear and apple orchards are relatively permanent habitats which host a great diversity of natural enemies, from different arthropod families, that regulate the populations of phytophagous species 17 . Predatory hemipterans, such as anthocorids and mirids, spiders and ants have been reported as key groups of natural enemies in pear orchards 1,20–28 . However, the importance of these groups of predators for the control of pear psyllids seems to vary among regions.…”