Cold hardiness and supercooling point of the female redbay ambrosia beetle (Xyleborus glabratus)- implications for invasion potential in the northern latitudes of North America

The invasive redbay ambrosia beetle (Xyleborus glabratus Eichoff) (Coleoptera: Curculionidae: Scolytinae) is endemic to parts of Asia and was introduced into the southeastern United States in 2002. The beetle carries Raffaelea lauricola T.C. Harr., Aghayeva, & Fraedrich, a newly described fungal symbiont responsible for a wilt disease that affects most lauraceous species of North America. Since introduction into the southeast U.S., the beetle and its associated fungal pathogen have devastated redbay (Persea borbonia (L.) Spreng.) and swampbay (Persea palustris (Raf.) Sarg.) populations along the Atlantic and Gulf Coastal Plains. More recently, laurel wilt has spread into sassafras in Alabama, Florida, and Mississippi; populations of sassafras range into southern Ontario, Canada. Additionally, very little is known regarding the physiology of the beetle or the effects of low temperature on its invasive potential into northern forests of North America. To understand physiological limitations of low temperatures on X. glabratus, the supercooling point (SCP) of the female redbay ambrosia beetle was experimentally determined during the summer of 2011. Live beetles were trapped in Jackson County, Mississippi using Lindgren funnel traps baited with manuka oil lures and redbay slash. The average supercooling point of female X. glabratus was -21.7 ºC ± 0.5 ºC (± SE). The SCP data points ranged from -10.3 ºC to -27.0 ºC (n = 48). Beetle size and weight had no affect on SCP. A significant (F = 27.4; p < 0.0001) negative trend in SCP temperature was found as the study progressed, possibly indicating an increase in cold hardiness. Based on the mean SCP of X. glabratus, laurel wilt disease could theoretically impact Lauraceae throughout North America. It remains unknown if X. glabratus invasion into northern latitudes of North America may be limited by the effects of low temperature warmer than the SCP reported herein. Ongoing chemical analyses of chill injured beetles will offer improved estimates on the sub-lethal effects of low temperature and invasion potential of X. glabratus into northern forests of North America.