After pine wilt disease (PWD) at Korean pine, Pinus koraiensis has been first reported in the middle area of South Korea in 2006, it spread rapidly to the nearest area. However, it is difficult to predict the spread of damage and set up the proper control strategy specific to P. koreaiensis because the pathology and the biology of PWD in P. koraiensis are not the same with PWD in P. densiflora and P. thunbergii distributed in middle southern area. So, we selected 25 of dead P. koraiensis in PWD damaged area and analyzed the inner-tree distribution of Bursaphelenchus xylophilus and the entrance holes of Monochamus saltuarius. There was no statistical significance between height or direction of wood extracted and the distribution of B. xylophilus among 25 dead pines. The entrance holes of M. saltuarius were concentrated on 7 dead pines without leaves and the maximum number of entrance holes in individual tree was 543. It indicates that the event of spawning of M. saltuarius adult and entrance of hatched M. saltuarius larvae to wood may be dependent on the time of death of host. The entrance holes were frequently found in a southward direction. These result shows that M. salutuarius larvae prefer relatively weak woody parts to enter easily. However, the relation between the thickness of bark of P. koraiensis and the frequencies of entrance holes of M. saltuarius was not observed.

Injection of nematicides such as emamectin benzonate and milbemectin is the most common practice to control the pinewood nematode, Bursaphelenchus xylophilus, in Korea. These macrocyclolactone nematicides, however, are expensive, limiting their practicability despite of high efficacy. In an attempt to screen affordable alternative organophosphate (OP) and carbamate (CB) nematicides, we identified and characterized three acetylcholinesterases (ACE, EC 3.1.1.7) from B. xylophilus and functionally expressed them using baculovirus system. In inhibition assay using 11 OPs and 3 CBs, all the three ACEs were highly inhibited by paraoxon, DDVP, chlorpyrifos-oxon and mevinphos of OPs and carbofuran and carbaryl of CBs but not inhibited well by the others. Interestingly, inhibition assay revealed that BxACE-3 is less sensitive to all insecticides tested than other two ACEs. In additional bioassay, chlorpyrifos, DDVP and parathion showed a high LC50 but all CBs tested did a very low mortality. The inhibition kinetic data and bioassay data obtained in this study should provide essential information for the development of OP-based nematicidal agents against B. xylophilus. Availability of expressed ACE will also facilitate the development of in vitro screening system to develop potential OP nematicides.