Not known to transmit any human or animal pathogens.

Several fungi have been isolated from T. fuscum and Tetropium spp., including some pathogenic fungi, but the beetles' status as a vector of pathogenic fungi to living trees remains unclear.

When trapping for woodborers or bark beetles, separate traps with different lure combinations by at least 100 feet.

Attaching lures to traps

IMPORTANT: Do not include lures for other target species in the trap when surveying for this target.

Geranyl acetol is commonly known as fuscumol.

The combination of lures for Tetropium fuscum is also effective for T. castaneum. If Tetropium fuscum is listed as a survey target in a work plan, then T. castaneum must also be listed in the work plan. 

All three lures listed are necessary to trap for this species.

The release rates of these lures are highly temperature-dependent. However, CAPS has listed a conservative length of effectiveness that will be effective for even the warmest weather in the CAPS community.

Note: Visual surveys are not an approved method and cannot be used to report negative data, but we are including some visual guidance to help surveyors who may observe signs of infestation. 

Signs of infestation include:

• White resin flowing along the length of the trunk. 
• Feeding tunnels filled with fine excrement and fiber that form an irregular net of galleries of up to ¼ in. Eventually, the trunk of the tree looks girdled.
• Adult exit holes are rounded oval, roughly 1/6 to 1/4 in diameter, and may or may not be plugged with coarse sawdust.

See the Pest Datasheet for images.

Surveys should take place from the end of spring through the summer. In its native range and Canada, adults emerge from May through August, with activity (flying and mating) peaking in mid-June.

Surveyors should perform pheromone trapping with cross vane panel traps. 

Trap placement: Place traps within 300 ft. of potential host trees. Traps should be spaced at least 80-100 ft. apart. Traps should be placed out of direct sunlight and should not be obscured by vegetation. Hang traps on stands or from rope with the bottom of the trap 8 to 20 inches above the ground.

Survey for T. fuscum in spruce forests and/or managed areas with hosts grown for timber. Focus survey efforts on forests with Picea rubens (red spruce) and Picea abies (Norway spruce), especially in areas with old and/or recently felled or stressed trees. For example, forests recently stressed by factors such as severe heat, diseases, and/or insect attack are preferred by T. fuscum and are an ideal target for survey.

Surveyors can also place traps in wood processing facilities, warehouses, wood recycling locations, and landfills that are close to woodlands.

• CAPS screening aid for spruce longhorn beetles, Tetropium spp.
• Cherepanov (1990) provides a key to larvae, pupae, and adult Tetropium species from North Asia, including T. fuscum and T. castaneum.
• Crowley et al. (2025) published the genome sequence for T. fuscum, which could be useful for molecular identification of this beetle.

The genus Tetropium can be distinguished from other genera within the Spondylidinae subfamily by the eyes, which are divided into two lobes by a strong indentation (See Fig. 3B in the Pest Datasheet). Within the genus Tetropium, adult beetles are difficult to differentiate, even when comparing native and exotic species, because they look similar in body shape and appearance. 

Native Species

Tetropium speciespresent in the United States include T. abietis, T. auripilis, T. cinnamopterum, T. parallelum, T. parvulum, T. schwarzianum, and T. velutinum. Of these, the most common species in North America are T. cinnamopterum, T. parvulum, and T. velutinum. 

Tetropium fuscum can be distinguished from other Tetropium present in eastern North America (T. cinnamopterum and T. parvulum) by the tiny, tooth-like projections on the surface of the pronotum and a distinct wide band of pale pubescence at the base of the elytra. Tetropium spp. present in other regions of North America (T. abietis, T. auripilis, T. parallelum, T. schwarzianum) can be differentiated from T. fuscum by looking at the features of the pronotum, head, and metatrochanter with the aid of a microscope. For images and a more detailed description of the morphological features used to distinguish T. fuscum from other native Tetropium spp., see the Pest Datasheet or the Tetropium spp. Screening Aid.

• Tetropium abietis is present along the West Coast, from Washington to southern California. Hosts include juniper and fir.
• Tetropium auripilis is present in southern Arizona, and there is limited information on this species. We found no host information.
• Tetropium cinnamopterum is found throughout the coniferous belt of North America, attacking spruce and pine.
• Tetropium parallelum is present in Arizona, Colorado, and New Mexico, with hosts including fir and spruce.
• Tetropium parvulum is found throughout the coniferous belt of North America in spruce and pine.
• Tetropium schwarzianum is present from Minnesota east to Nova Scotia and south to North Carolina in spruce and pines.
• Tetropium velutinum is found from the central western U.S. and western Canada to Alaska, in larch, hemlock, and Douglas fir.

Exotic Species

Tetropium spp. not present in North America that are similar to T. fuscum include T. castaneum and T. gabrieli. See the Pest Datasheet for images.

• Tetropium castaneum can be distinguished from T. fuscum based on its pronotum, which is smooth and shiny, while that of T. fuscum looks coarsely granular and dull. Also, the antenna in T. fuscum is thin, whereas in T. castaneum it is thick with distinct nodes. Tetropium castaneum prefers spruce and fir,but can use larch and pine species, which implies it may be more polyphagous than T. fuscum.
• Tetropium gabrieli can be differentiated from T. fuscum by the lack of the lengthwise groove between the base of the antenna, which is present in T. fuscum. It prefers larch as a host.