Extreme low temperature tolerance of Leptocybe invasa.
Leptocybe invasa Fisher & La Salle is a new, quarantinable, invasive species. In order to clarify the extreme low temperature tolerance and potential range of this pest we measured the supercooling and freeezing points of all life stages except the egg. Adult L. invasa live at different latitudes and have varied hosts. The larvae overwinter in three southern Chinese provinces from December to March. The relative supercooling and freezing points of three life stages was pupa < larvae < adult. The supercooling and freezing points of pupae were (-24.93±0.05) °C and (-22.81±0.02) °C, respectively, and the supercooling and freezing points of adults were (-20.93±0.27) °C and (-17.33±0.17) °C, respectively. Supercooling and freezing points decreased with increasing latitude. The relative supercooling and freezing points of L. invasa on different hosts in Hainan Province were Zhan-201 < Eucalyptus exserta < Guanglin nine. Supercooling and freezing points of L. invasa are rising with increasing environmental temperatures. The lowest supercooling and freezing points of overwintering larvae, (-25.44±0.17) °C and (-24.04±0.21) °C, were recorded in Guangzhou city in January when the temperature was the lowest in four months. The lowest recorded supercooling point of an individual was -26.9°C. Our results reveal stronger cold hardiness in the pupa and egg stages than in larvae or adults. Latitude, host and temperature have an appreciable impact on cold hardiness. The results suggest that this pest has the potential of spreading further north.