Christchurch, New Zealand.

Pinus kesiya Royle ex Gordon plantations are of major economic, social, and environmental importance to the Lam Dong province of Vietnam. Pine wilt symptoms and dead trees are found in pine plantations at various locations. A systematic survey was needed in order to identify the nematode and its vector, the Japanese sawyer beetle Monochamus alternatus Hope, and to evaluate the incidence and severity of the disease. The health status of the trees (disease incidence) was evaluated by measuring the amount of oleoresin exudation after holes were punched in pine stems. Experimental plots within pine stands were typically 400 m2. Disease incidence was assessed as 36.5%, 46.4%, 47.9%, and 48.0 % in Lang Bian, Phi Lieng, Cam Ly, and K’Long K’Lanh respectively. The death rate of pine trees increased annually and was dependent on the density of plantations. Yearly losses in the high density plantations were higher than in the lower density plantations. Nematodes extracted from wood samples were identified as a species of Bursaphelenchus. The recovery of nematodes from affected trees varied between specimens collected from different locations. The highest densities of nematodes were found in samples collected at K’Long K’Lanh and Cam Ly. Based on the morphological characteristics of adult sawyer beetles, all were identified as the Japanese sawyer beetle. Sawyer beetles have two emergence periods each year, the first lasting from the end of March to early July and the second from September to the end of October. The largest numbers of adults emerged at the end of April and at the end of September. Stems of 3-year-old Pinus kesiya were inoculated with cultured nematodes and the pathogenicity of the Bursaphelenchus sp. was demonstrated