Evaluating vacuum and steam process on hardwood veneer logs for export

There is an immediate need to develop and adopt new treatment technologies for eliminating insect pest and tree pathogens from veneer logs moved in trade. This is largely due to the current phase-out of methyl bromide and the uncertainty associated with the efficacy of potential alternatives. Vacuum and steam in combination has a proven and reliable record for commercially sanitizing a variety of commodities, including cotton, spices and textiles among others. This study was designed to evaluate basic parameters of vacuum and steam application on five high value hardwood veneer log species in an effort to ascertain the feasibility of continued treatment development. Relative heating rates to log center, damage and value loss assessment due to treatment, and overall energy used during treatment were recorded for logs treated individually in a flexible polymer chamber. At 200 mm Hg vacuum, time to reach 56 A degrees C for 30 min to core ranged from 17 to 29 h, depending on density and log diameter. End checking varied by species, but veneer sawn from logs was largely unaffected in terms of yield and value. Energy used during treatments ranged from 54 to 205 kWh for individual logs. Results suggest that vacuum and steam as a phytosanitary treatment for hardwood veneer logs has potential and should be explored further.