The presence of beneficial arthropods in organic versus IPM pear orchards and their ability to predate pear suckers (Cacopsylla pyri)

In Belgium, two cultivation methods of pear are widely applied, namely organic farming and integrated pest management (IPM). Organic pear orchards are characterized by the use of green techniques such as natural fertilizers and the restricted use of crop protection products, whereas integrated pest management combines a well-tuned integration of biological pest control and crop protection treatments. It is generally considered that these two cultivation methods have different effects on the density of beneficial arthropods in the orchard and the occurrence of common pests as well. Therefore, a large-scale monitoring study was executed comprising extensive samplings throughout the year in 14 pear orchards and comparing beneficial fauna population developments between organic and IPM pear orchards. Pear sucker (Cacopsylla sp. or pear psylla) which is considered the major pest of pear in Belgium, was monitored as well. Organic orchards clearly displayed a lower pear psylla pressure correlating with higher proportions of specific predator populations, particularly velvet mites (Trombidiidae) and spiders (Araneae). IPM orchards showed higher numbers of Anthocoris spp. in summer. In addition, predation of C. pyri was verified by PCR-based gut content analysis. Regarding the results of this prey-predator PCR, Anthocoridae had the highest chance for detection of psyllid DNA in their gut. Velvet mites also scored particularly well for the PCR detections, indicating that other arthropods besides Anthocoridae could have an impact on the psyllid pressure in a pear orchard.

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