Cold Hardiness Of Monochamus Alternatus, As The Key Vector Of Invasive Nematode, Bursaphelenchus Xylophilus

The Japanese pine sawyer, Monochamus alternatus, is the most important vector transmitting the pine wood nematode, Bursaphelenchus xylophilus, as an agent of pine wilt disease. To assess the cold hardiness and potential dispersal ability of Monochamus alternatus, we examined the parameters of cold hardiness of all developmental stages of the beetle, in particularly overwintering 4⁵th instar larvae, involving supercooling points (SCPs), lethal time and acclimation efficiency.The mean SCPs of the eggs, overwintering larvae, pupae, and adults of the beetle were significantly different, with the eggs having the lowest mean SCPs (-19.8±0.2°C) and the adults having the highest (-6.6±0.3"C). Significant differences were not observed between the means SCPs of overwintering larvae (-14.5±0.4"C) and pupae (-15.0±0.5"C). When exposed to serial temperatures, they did not survive at -25°C, and overwintering larvae had the strongest cold hardiness. The mean SCPs declined from -11.9°C to -15.7 °C with development of the overwintering larvae instars.Range of SCPs of overwintering 4^5th larvae was -20.0°C^-15.7"C. The mortality of overwintering 4⁵th larvae increased as decrease of the temperature and prolongation of exposed duration at low temperature, and they did not survive at -25°C. Lt₅0 and Lt95 were 35.8d and 65.4d at -10°C, respectively. It was showed that -10°C was theoretically the Upper Limit of Chill Injury Zone by the equation of there-dimensional model of relation among mortality and temperatures and times, M(t,T)=e^{-1.940-0.139×t×(T+9-638)}/(1+ e^{-1.940-0.139×t×(T+9-638)}). Acclimation did not promote the cold hardiness of overwintering 4^5th instar larvae.Combined the parameters of cold hardiness of the beetle with geographically climatic data of China, the -10°C isotherm of January mean air temperature was suggested as the northern limit of the beetle distribution in China. Moreover, distribution and monitoring of the beetle in Shanxi was that Wutai Mountain forest zone, Guanchen Mountain forest zone and Heicha Mountain forest zone in the north belonged to the non-survival region; Guandi Mountain forest zone, Taihang Mountain forest zone, Lvliang Mountain forest zone and Taiyue Mountain forest zone in the middle belonged to the potential dispersal region; Zhongtiao Mountain forest zone in the south belonged to the suitable distribution region. These researches are used to systematically instruct controlling of plant diseases and insect pests.