Survival of Bursaphelenchus xylophilus in wood chips
In Canada, in vitro studies have been carried out on the survival of two isolates of Bursaphelenchus xylophilus (EPPO A1 quarantine pest) in wood chips. The wood chips were composed of a mixture of Pinus contorta var. latifolia, Tsuga heterophylla and Pseudotsuga menziesii and were fumigated with methyl bromide before inoculation of the nematodes. After 4-6 weeks of incubation at 20-22 °C, nematode numbers stabilized at about 50 % of the original inoculum (approximately 2000 nematodes per sample of 6-7 g of wood chips). It was found that B. xylophilus was able to survive in low numbers at
20-22 °C for up to 14 months (British Columbia isolate) or 20 months (Alberta isolate).
20-22 °C for up to 14 months (British Columbia isolate) or 20 months (Alberta isolate).
In addition, the effects of temperature (10, 20, 30, 40 °C), relative humidity (52, 75, 85, 100 %), and time (4, 10, 20, 30 days) on the survival of B. xylophilus in wood chips were analysed. Statistical analysis showed that significant effects were produced by temperature, time and isolate. It was observed that only the combinations of 40 °C and 30 days (irrespective of RH and isolate) and of 40 °C, 20 days and 52 % RH killed all the nematodes in wood chips. However, the authors considered that these combinations were not convenient for treatments of large quantities of wood chips because of the long exposure times involved.
The body length and lipid level of the nematodes present in the wood chips indicated that a high proportion of the population was probably composed of dispersal third-stage larvae, although the average length was less that previously reported for B. xylophilus.
Though the authors concluded that the introduction of pine wilt disease into European countries by means of infested wood chips would depend also on several other biological and climatic factors necessary for nematode transmission, this study confirms that B. xylophilus can survive (and most probably as the dispersal third-stage larvae) in wood chips.
Sources
Panesar, T.S.; Peet, F.G.; Sutherland, J.R.; Sahota, T.S. (1994) Effects of temperature, relative humidity and time on survival of pinewood nematodes in wood chips.
European Journal of Forest Pathology, 24 (5), 287-299.