Temporal changes in emerald ash borer overwintering physiology: implications for range expansion

The Emerald Ash Borer, Agrilus planipennis, is an invasive beetle that is causing extensive damage to ash trees in North America. Native to eastern Asia, it has been spreading steadily since its introduction. Cold is commonly considered a limiting factor in determining species ranges, but it is currently unknown what effect low winter temperatures may have on limiting the spread of A. planipennis, as little is known about its cold tolerance. Here, I determine temporal changes in low temperature tolerance of A. planipennis from late fall to early spring. The overwintering stage of A. planipennis is freeze avoiding, with mean supercooling points being lowest in January (-30.5°C) and increasing to -23.5°C in April. Supercooling points are lowered using a combination of antifreeze proteins and increased hemolymph osmolarity. These results will help to evaluate the potential of this species to spread northwards in Canada.