Assessments of Rhagoletis pomonella (Diptera: Tephritidae) infestation of temperate, tropical, and subtropical fruit in the field and laboratory in Washington State, U.S.

To understand the likelihood of any risk of apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), to domestic and foreign fruit export markets, knowledge of its host plant use is needed. Here, assessments of R. pomonella infestation of temperate, tropical, and subtropical fruit were made in the field and laboratory in Washington State, U.S. In field surveys in 2010– 2017 in central Washington, 6.7% of Crataegus douglasii and 6.1% of feral Malus domestica trees (both temperate plants) in fly-managed (insecticide- treated) sites were infested by larvae. In unmanaged sites, 54.1% of C. douglasii and 16.3% of feral M. domestica tree samples were infested. In field surveys of 36 types of temperate fruit in 2015–2018 in southwestern Washington, new host records for R. pomonella were one species and three hybrids of Crataegus, as well as Prunus domestica subsp. syriaca – all of which produced adult flies. In addition, Prunus avium was a new host record for Washington State, producing one adult fly. Prunus armeniaca x Prunus salicina and Vitis vinifera exposed to flies in the laboratory produced adult flies. Of 37 types of tropical and subtropical fruit hung in fly-infested M. domestica trees in southwestern Washington, only Mangifera indica produced puparia. Out of nine tropical and subtropical fruit types in laboratory tests, Musa acuminata x balbisiana produced puparia but no adult flies. Results provide a basis for further research and hypotheses concerning host use by R. pomonella and its potential impact on protecting both U.S. and tropical and subtropical fruit markets