Diversity, biology, and management of the pear psyllids: a global look

The pear psyllids (Cacopsylla Ossiannilsson; Hemiptera: Psylloidea: Psyllidae) are a taxonomically difficult group of at least 24 species native to the Palaearctic region. One or more species occur in most pear-growing regions, in some cases as invasive introductions. Existing reviews of this group are primarily of taxonomic focus with limited overviews of biology. The earliest biological studies of the pear psyllids centered on a core group of a few western European species. In part, this focus arose because diversity of the pear psyllids was poorly understood. As taxonomic understanding has advanced over the last 3 decades, research has expanded taxonomically. Increasing difficulties in controlling the pear psyllids additionally has contributed to growth in research. Here, we review a now-extensive literature on diversity, biology, and management of the pear psyllids. Three broad observations emerged from this synthesis. First, large gaps in biological understanding of the pear psyllids persist for several geographic faunas, most notably for psyllids of the Eastern Palaearctic region. Second, taxonomic diversity is accompanied by biological diversity. Despite the commonality in host use among the pear psyllids, with each species being limited to development on Pyrus, striking differences exist among species in life cycles, wintering, and other biological traits. Third, many of the tools being used to manage pear psyllids today are in existence because of the long history of basic research which has targeted these pests. These tools include new insecticides of higher selectivity, various cultural and horticultural tactics, and practices that conserve natural enemies in orchards.