Document Type

Thesis

Date of Degree Completion

Winter 2018

Degree Name

Master of Science (MS)

Department

Biology

Committee Chair

Dr. Jason Irwin

Second Committee Member

Dr. Alison Scoville

Third Committee Member

Dr. Michael Bush

Abstract

The brown marmorated stink bug, Halyomorpha halys, is native to eastern Asia and is an invasive pest in the United States. Limited research has been done regarding the factors influencing this species’ winter survival within invaded northern regions. Cold tolerance has been previously evaluated in the eastern United States, bot nut within western populations. Winter diapause. Along with any potential links between diapause and cold tolerance remain unstudied. I examined characteristics of cold tolerance, diapause and overwintering sites to evaluate the factors contributing to the winter survival and, ultimately, persistence of this pest within central Washington. This study measured seasonal changes in cold tolerance of H. halys by determining its cold tolerance strategy and supercooling ability via the supercooling point (SCP). Metabolic suppression (as measured by flow-through respirometry) indicated that diapause was induced by a critical photoperiod of 11h:13h (L:D), indicating a process potentially influenced by multiple environmental factors. Also at this time, females no longer had developed eggs in the ovaries, indicating reproductive arrest. Overwintering sites monitored with temperature dataloggers measured daily minimum temperatures at an outdoor enclosure and naturally-selected overwintering site. We verify that populations of H. halys are chill-intolerant (i.e. a portion of individuals die prior to freezing) with minimum cooling temperatures between -10 °C and -15 °C causing survival rates to drop in field and lab populations by 73% to 6% and 86% to 14%, respectively. Cold tolerance significantly differed by light-hour regime (F(3) = 4.55, p-value = 0.0048), sex (F(1) = 9.49, p-value = 0.0026), and mass (F(2) = 4.62, p-value = 0.033). The mean supercooling point (± SEM) of individuals in central Washington was -12.6 ± 0.2 °C. Diapause was observed to be a prerequisite to achieving maximum levels of cold tolerance and must also involve a subsequent period of cold acclimation. Given their extent of cold tolerance, I conclude that under natural conditions, H. halys cannot effectively survive winters within Central Washington State, a conclusion supported by the 100% mortality in an outdoor population. To persist in this region, H. halys will likely need to rely on human-built thermally-insulated refugia.

Available for download on Wednesday, April 29, 2020

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