Steam and Vacuum Treatment of Large Timber in Solid Wood Skids

Abstract

Forest pests are commonly transported along with wood packaging materials. Ports in the United States continue to intercept invasive pests in cross-section timbers that are packaged with steel or heavy consignments. The large cross-section timbers present a greater risk because the fumigation and kiln treatments that are currently used in treating wood packaging materials are not effective on large cross-section materials. The objective of this study is to determine the effectiveness of steam and vacuum for heat-treating large cross-section timbers in wood skids and crates, according to the heat-treating requirements of ISPM 15 (IPPC 2013) specifying 56 °C for a minimum of 30 minutes throughout the profile of the wood. Three wood species of large dimension timbers were tested. The timbers were partially air-dried to moisture contents for poplar at 39.1% MC, pine 38.3% MC, and oak 60.6% MC. Larvae of the pinewood sawyer beetles (Monochamus spp.) were used as a representative surrogate for invasive cerambycids. The initial vacuum pressure was 100 mm Hg and the test chamber temperature was set for 90 °C. The treatment cycle was continued until the core temperature of the large timber reached the required 56 °C for 30 min. To measure the temperature profiles within the timbers, thermocouples were placed at various locations. After each test, the larvae were recovered and assessed for mortality.