Heat as a phytosanitary treatment for the brown spruce longhorn beetle

Abstract

The brown spruce longhorn beetle (BSLB), Tetropium fuscum (Fabr.), is native to Europe but has recently been discovered in Halifax, Nova Scotia, where efforts are underway to eradicate it. If attempts to eradicate this beetle are unsuccessful, phytosanitary measures will have to be developed to ensure continued access to markets. We carried out studies to determine the lethal temperatures for different BSLB life stages in spruce. The beetles were exposed to different temperatures for various time periods in lumber of low and high moisture content. Adults died after 30 and 15 minutes exposure to 40 and 45°C, respectively, and pupae died after 30 minutes exposure to 45°C. Larvae required exposure to 50°C for 30 minutes (or 55°C for 15 minutes) to ensure 100% mortality. Larval survival was slightly higher in wood with low moisture content. The study was repeated a second year for the 50°C/30-minute and 55°C/15-minute treatments for larvae and the 45°C/30-minute for pupae at very low moisture (12-15% oven-dry basis) content, with similar results. Our results demonstrate that heat treatment is an effective phytosanitary method to ensure that wood does not contain any live BSLB.Current phytosanitary guidelines listed by the Canadian Food Inspection Agency in its directive "Canadian Heat-treated Wood Products Certification Program (CHTWPCP) for Export" (56ºC, 30 minutes) are more than adequate to ensure BSLB-free wood. Key words: brown spruce longhorn beetle, heat treatment, hygrothermal stress, Tetropium fuscum, wood borers