Factors influencing Trechnites spp. abundance in WA and OR pear orchards

Authors: Zilnik, Gabriel; NOTTINGHAM, LOUIS - Washington State University; Cooper, William - Rodney; ADAMS, CHRIS - Oregon State University; Horton, David; HILTON, RICK - Oregon State University; Schmidt, Rebecca

Submitted to: Western Orchard Pest and Disease Management Conference
Publication Type: Abstract Only
Publication Acceptance Date: 11/29/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pear psylla is the most important insect pest of pear in the Pacific Northwest. The pest causes fruit staining, leaf loss, reduced tree growth and, in serious cases, tree death. Large infestations can cause reduced yield due to pickers refusing to harvest sticky, honey-dew covered fruit. The main control tactic is chemical insecticide applications. Growers make 10-20 applications per orchard every year, spending roughly $2,000/acre. Unfortunately, the currently used chemicals for pear psylla management have limited utility due to pesticide resistance development. Biological control by pest natural enemies is an underused alternative to insecticides. As pesticides lose effectiveness, growers are interested in relying more heavily on natural enemies. Trechnites insidiosus is the major parasite of pear psylla in the Pacific Northwest. In orchards using fewer or less harmful chemicals, parasitism rates of pear psylla can approach 80%. Despite its likely value in pears, little is known about the biology of Trechnites. This includes what factors influence Trechnites abundance in pear orchards. In this study, researchers from the USDA-ARS in Wapato, WA, in collaboration with Washington State University and Oregon State University, placed 3D-printed tube traps in pear blocks across the Pacific Northwest from Medford, OR up to Tonasket, WA to monitor Trechnites and pear psylla. The orchards with varied in land usage, spray programs, and acreage. This presentation will summarize data on the factors that affect Trechnites abundance in pear orchards. This will allow growers to select management practices that best conserve this important natural enemy, reducing reliance on insecticides

Technical Abstract: Pear psylla (Cacopsylla pyricola) is the most important pest of pear in the Pacific Northwest. The pest causes fruit russet, defoliation, stunting and, in serious cases, tree death. Large infestations during the season can cause reduced yield due to pickers refusing to harvest sticky, honey-dew covered fruit. Chemical insecticides remain the predominate management tactic, with approximately 10-20 applications made per orchard annually amounting to 46% of the total pest management costs. Biological control is an underutilized alternative to chemical pesticides. As pesticides continue to lose their efficacy due to resistance, growers are increasingly interested in biological control agents. Trechnites spp. (most commonly T. insidiosus) is the predominant parasitoid of pear psylla in the Pacific Northwest. In orchards practicing softer management programs parasitism rates of pear psylla can approach 80%. Despite its potential utility in pears, little is known about the biology of Trechnites spp. including what factors influence Trechnites spp. abundance in pear orchards. In this study, we placed 3D-printed tube traps in pear blocks across the Pacific Northwest from Medford, OR up to Tonasket, WA. These traps passively catch pear psylla and Trechnites spp. in a vial of antifreeze which allows for later processing and preserves the specimens for molecular analysis. We chose orchards with varying land usage, spray programs, and acreage. We will present a preliminary analysis on the factors that influence Trechnites spp. abundance in pear orchards