Regional distribution and cold hardiness of Monochamus alternatus and M. saltuarius in Korea

Monochamus alternatus and M. saltuarius were reported as the vectors of Bursaphelenchus xylophilus, pine wood nematode in Korea. They have occupied their own geographical distribution : M. saltuarius in southern part and M. alternatus in mid-northern part of Korean peninsula. We measured the supercooling point (SCP) of 2 species (laboratory-reared population) by each developmental stage. The SCPs of 2nd, 3rd, 4th and 5th instar larvae of M. saltuarius were -7.68}0.19Ž, -7.02}0.69Ž, -3.70}0.62Ž, -4.93}1.34Ž, respectively. On the other hand, the SCPs of 3rd, 4th, 5th instar larvae and pupae of M. alternatus were -4.46}1.12Ž, -5.94}1.33Ž, -7.83}1.44Ž, -9.53}1.78Ž, respectively. The pupae of M. alternatus and 2nd instar larvae of M. saltuarius had the lowest SCP. The highest SCP was recorded in 2nd and 4th instar larvae, each. Interestingly, the SCP of M. alternatus gradually deceased by their developmental stage. However, there were no apparent correlation between the SCPs and developmental stage in M. saltuarius, differently to the assumption that regional distribution of 2 beetles may be associated with the adaptation capacity to low temperature represented by SCP as well as their growth temperature. However, the samples tested didnft collect from fields we are preparing additional experiments with both nationwide and indoor-reared population.