DISTRIBUTION AND REPRODUCTION OF BURSAPHELENCHUS-XYLOPHILUS POPULATIONS IN WOOD AND BARK OF WESTERN NORTH-AMERICAN CONIFERS

The growth of populations of Bursaphelenchus xylophilus in wood and ba rk of Abies grandis, Pinus contorta, Pseudotsuga menziesii, Tsuga hete rophylla and Thuja plicata was Studied. Nematodes were inoculated into 6 cm diameter x 25 cm long stem segments of each tree species and inc ubated in plastic bags at room temperature (22 +/- 4 degrees C). Nemat ode populations in the wood and bark were sampled separately at 4, 8 a nd 16 weeks after inoculation. Mean population densities in wood (pool ed over sample dates) were 233, 13, 12, 2 and 0.03 nematodes/g dry woo d for P. contorta, P. menziesii, A. grandis, T. heterophylla and T. pl icata, respectively. Population densities in bark of the same species were 70, 267, 88, 113, and 21 nematodes/g dry bark, respectively. Nema tode population growth was also studied in finely chopped autoclaved a nd non-autoclaved wood and bark of each tree species, and on filter pa pers impregnated with ethanol extracts of P. contorta and P. menziesii sapwood. Nematode population densities were greatest in P. contorta f or both the autoclaved and non-autoclaved wood. After 6 weeks, populat ion densities in non-autoclaved wood of P. contorta, P. menziesii, A. grandis, T. heterophylla and T. plicata was 137, 46, 5, 23 and 1 nemat odes/g dry wood, respectively. Nematode populations grew more rapidly on filter papers impregnated with P. contorta extract than on filter p apers impregnated with P. menziesii extract.