The term “cedar beetle” is a common name referring to several insect species, causing confusion about the actual risk they pose. The most common insects associated with this name are the harmless Sandalus niger and the destructive wood-boring beetles from the Buprestidae family. While adult beetles are generally not a threat to people or pets, the larval stage of the wood-boring species is the primary concern for property owners. The real danger is almost entirely economic and structural, stemming from the larvae’s ability to tunnel through cedar and cypress wood.
Identifying the Cedar Beetle
Accurate identification is important because the “cedar beetle” group includes insects with vastly different behaviors. The Western Cedar Borer (Trachykele blondeli), a flat-headed borer, is a major pest often associated with the name. This adult beetle measures 11 to 17 millimeters long and is typically a striking metallic emerald green with a golden sheen.
Adults are strong fliers characterized by their flattened, elongated bodies. Another common type is the Flatheaded Cedar Borer (Chrysobothris nixa), which is slightly smaller, ranging from 9 to 14 millimeters, and is metallic brown to black. While adults are often spotted emerging from wood, their legless, pale white larvae (grubs) cause significant damage by tunneling beneath the bark.
Assessing Personal Risk to Humans and Pets
Cedar beetles pose virtually no direct health risk to humans or household pets, regardless of the specific species. The common Sandalus niger is a non-toxic insect that does not bite, sting, or cause allergic reactions. Like most beetles, they do not attack people, suck blood, or transmit diseases.
Even wood-boring species, such as the Western Cedar Borer, lack defensive mechanisms that threaten mammals. They do not secrete toxic substances like blister beetles or spray irritants. Interaction with these insects is limited to being a nuisance or a sign of property damage, not a physical hazard. They are generally harmless if pets ingest them.
Threat to Wooden Structures and Vegetation
The danger associated with cedar beetles focuses almost entirely on the damage caused by larvae tunneling through wood, impacting the economic value of timber and tree integrity. Western Cedar Borer larvae primarily attack the heartwood of living cedar and cypress trees, often without visibly injuring the tree itself. Their tunneling activity, which can extend up to 13 meters, creates “wormy cedar” that significantly degrades wood quality. This renders the wood worthless for high-grade products like shingles, finished lumber, and utility poles.
Flat-headed borers are often secondary pests, preferring to infest trees or shrubs already stressed, injured, or weakened by factors like drought. When borers emerge from lumber used in construction, the holes they leave are primarily cosmetic because the larvae in seasoned wood are already dead. Since emergence from dried wood does not lead to re-infestation, the risk to the structural strength of an established building is typically low. The true threat is to the standing timber industry and the health of stressed landscape trees.
Safe Management and Prevention
Prevention of cedar beetle infestation centers on maintaining the health of susceptible trees and controlling moisture around wooden materials. Wood-boring beetles often target stressed trees, so ensuring proper site conditions and providing long, slow, deep watering during dry periods is recommended. Mulching can help support the tree’s overall health, though fertilization is generally not suggested.
For structural concerns, the best approach is ensuring that cedar wood used in construction is properly seasoned, as larvae cannot survive in dried lumber. Homeowners can use exclusion techniques, such as sealing cracks and crevices around the foundation, to prevent adult beetles from seeking entry points. For existing infestations in trees, aggressive chemical treatment is often ineffective once larvae are established. Therefore, removing and destroying infested branches or dead wood is the most effective management strategy.