Heat-treating and drying southern pine lumber infested with pinewood nematodes.
Dwinell L.D.
The European Economic Community is considering regulations, including a kiln-dried requirement, for all imported coniferous sawnwood in order to protect European forests from exotic tree pests such as the pinewood nematode, Bursaphelenchus xylophilus. The pinewood nematode is transmitted when its insect vector, the pine sawyer (Monochamus spp), lays its eggs in freshly cut, felled, dying, or recently dead conifers. Therefore, the nematode may occasionally be present in green lumber. This study was undertaken to determine if the nematode could survive in heat-treated and kiln- or air-dried southern pine lumber. A series of experiments was conducted using lumber sawn from logs colonized by pine sawyers and infested with pinewood nematodes. Nematodes were eradicated from green lumber by kiln-drying. Furthermore, heat-treating lumber in a 71 degrees C kiln to a wood temperature of 60 degrees was sufficient to kill all nematodes. The time varied with the dimension af the lumber. For example, 1 hour for 2 by 4's and 4 hours for the 6 by 6's. This length of time did not appreciably change the wood moisture content of the lumber. This study indicates that it is not necessary to kiln-dry lumber for the sole purpose af eradicating pinewood nematodes. The nematodes survived in air dried pine lumber for more than 2 months and adult pine sawyers emerged. The same temperature schedule that eliminates pinewood nematodes would be effective in eradicating pine sawyers. Alternative control strategies and a mill certification program are also discussed.
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