Biology and management of pear psylla (Hemiptera: Psyllidae) in the Pacific Northwest

Abstract Pear psylla, Cacopsylla pyricola (Foërster), is the most economically harmful arthropod pest of pears in the Pacific Northwest (PNW). The phloem-feeding nymphs produce a sticky, sugar-based excrement called honeydew, which causes cosmetic fruit injury, tree stress, and inconvenience to orchard workers. Management of pear psylla has historically prioritized season-long spraying with insecticides that have substantial nontarget effects on natural enemies. However, control has been an ongoing challenge in many growing regions due to pear psylla’s resistance to insecticides, and natural enemies are virtually absent in orchards with aggressive pesticide programs near harvest, leading to rapid increases in pear psylla. Subsequently, excessive numbers of overwintering pear psylla create a regional overabundance of the pest the following spring. Integrated pest management (IPM) programs for pear psylla prevent this cycle with effective cultural tactics and insecticides that are minimally disruptive to natural enemies. Still, IPM adoption seems to be regionally variable. The major growing region of the Wenatchee Valley in Washington State has been reluctant to adopt IPM and, consequently, continues to struggle with pear psylla management. Other areas, such as Hood River, Oregon, and Okanogan, British Columbia, have made significant improvements in pear psylla management through the adoption of area-wide IPM. This review will provide an overview of pear psylla biology, pest status in the PNW, primary IPM tactics, and various elements that have either challenged or advanced the pear industry’s adoption of IPM.