Relationship of Bursaphelenchus xylophilus Population Density to Mortality of Pinus sylvestris
Melakeberhan, H.; Webster, J.M.
Journal of Nematology 22(3): 297-302
1990
ISSN/ISBN: 0022-300X PMID: 19287724 Document Number: 348046
Seven-month-old Scots pine (P. sylvestris) seedlings were inoculated with water or culture filtrate (controls), with 10 000, or 20 000 (experiment 1), and with 2500 (experiment 2) B. xylophilus B.C. isolate nematodes and maintained under defined experimental conditions. Controls did not develop pine wilt disease over a 2-month period. In experiment 1, less than 50% of the inoculum was recovered from the nematode-inoculated seedlings in the first 48 h, after which the nematode population of both treatments increased exponentially resulting in pine death and approximately equal populations at 216 h after inoculation. In the second experiment, plant mortality, which was always preceded by 2-3 days of chlorosis and associated stem vascular necrosis, first occurred 14 days after inoculation. The nematode population increased until about day 40 after inoculation and declined thereafter. Nematodes extracted from the roots 2 weeks after inoculation accounted for ca.15% of the total number of nematodes per pine. The study indicates that the rate of nematode reproduction is a factor in pine wilt disease. However, the lack of a linear correlation between the number of nematodes and the timing of pine mortality suggests that the timing of pine death may also depend on the location of nematode damage to the host tissue.