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Ambrosia Beetles

T. L. Shore

Introduction

Ambrosia beetles, or "pinworms" as they are often called in the forest industry, are a group of beetles totalling over 1000 species worldwide. In British Columbia there are at least five ambrosia beetle species affecting commercial timber: Trypodendron lineatum (Olivier), Gnathotrichus sulcatus (LeConte), G. retusus (LeConte), Platypus wilsoni Swaine, and Xyleborus saxeseni (Ratz.). Of these five species, T. lineatum beetles are the most abundant and damaging, followed by G. sulcatus (Figure 1) and, to a lesser extent, G. retusus . Most commercial conifer species are susceptible to ambrosia beetle attack but most damage occurs to Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg.), true firs (Abies spp.), and spruce (Picea spp.). The pinholes from their tunnels or galleries (Figure 2) and the dark staining of the wood caused by a fungus associated with the beetles occurs in the sapwood -the most valuable, clear portion of the log. Attack densities of over 2500 holes per square metre of log surface have been reported. This damage, although more of a technical than a structural defect, results in a reduction in grade (degrade) of the lumber or veneer product, greatly reducing its value. The ability of ambrosia beetles to attack, survive, and develop in green lumber has resulted in export and quarantine problems. For this reason, additional care has to be taken to keep damaged or infested material out of export shipments. This means additional costs due to extra handling, repackaging, and remanufacturing. Annual losses to the British Columbia forest industry as a result of ambrosia beetle damage have been estimated as high as $63 million per year (McLean 1985).

For more information, see the Ambrosia Beetles Forest Pest Leaflet in the Canadian Forest Service bookstore.