Not known to transmit any human or animal pathogens.

Not known to vector any pathogens or other associated organisms but damage may lead to invasion by secondary pests. Several fungi have been isolated from T. castaneum or Tetropium spp., including some pathogenic fungi, but their status as a vector of pathogenic fungi to trees in field settings remains unclear. 

Attaching lures to traps

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

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

Note: Visual surveys for damage or larvae 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.
• Adult exit holes, oval or circular, that are more concentrated on the lower trunk. 
• Girdled tree trunks.
• Tree crowns that fade from green to yellow and to reddish brown.
• Wood may be stained blue from associated Ophiostoma fungi.

(See the Pest Datasheet for images)

Surveys should take place from the end of spring through the summer. In its native range, adults fly from May-September, with peak emergence in June-July.

Surveyors should perform trapping surveys.

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. See additional guidance below.

Survey for T. castaneum in Picea spp. spruce forests and/or managed areas grown for timber. Focus survey efforts on Picea abies (Norway spruce) forests, especially in areas with old trees, recently felled trees, or stressed trees. For example, recently damaged forests, such as those affected by storms, wildfires, diseases, or other insects are an ideal target for survey.

• 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.
• There are multiple examples of various body measurements (morphometry) that can be used to distinguish closely related Tetropium species (see Goczal et al., 2017 and  Smith-Pardo et al., 2025 in the References Section below). 

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. 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 species present 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. 

The following information on morphological features to distinguish T. castaneum from other Tetropium spp. was compiled from the Tetropium spp. Screening Aid by Royals et al. (2019).

• Tetropium abietis can be differentiated from T. castaneum by the pronotum. In T. abietis, the pronotum looks rough because of multiple small puncture marks, while in T. castaneum, it appears smooth. It is present along the West Coast, from Washington to southern California, and has juniper and fir as hosts.
• Tetropium auripilis there is limited information on this species, including morphological features to differentiate it from T. castaneum. It is present in southern Arizona, but there is no available information on hosts.
• Tetropium cinnamopterum can be distinguished from T. castaneum by examining features of the metatrochanter that will need to be examined by a trained taxonomist. It isfound throughout the coniferous belt of North America. This beetle predominantly attacks spruce trees.
• Tetropium parallelum can be differentiated from T. castaneum by the pronotum. In T. parallelum, the pronotum looks rough because of multiple small puncture marks, while in T. castaneum, it appears smooth. It is present in Arizona, Colorado, and New Mexico, with hosts including fir and spruce.
• Tetropium parvulum can be distinguished from T. castaneum by examining additional features of the metatrochanter that will need to be examined by a trained taxonomist. It is found throughout the entire coniferous belt of North America, mainly in spruce but also in pine.
• Tetropium schwarzianum can be differentiated from T. castaneum by the weakly furrowed or absent frontal groove between the base of the antennae, which is deep in T. castaneum. Itis present from Minnesota to Nova Scotia to North Carolina in spruce and pines.
• Tetropium velutinum can be differentiated from T. castaneum by the pronotum. In T. velutinum, the pronotum looks rough because of multiple small puncture marks, while in T. castaneum, it appears smooth. It is found in the central western United States as well as western Canada and north to Alaska, in larch, hemlock, and Douglas fir.

Exotic Species

Tetropium spp. not present in the United States that look similar to T. castaneum include T. fuscum and T. gabrieli. 

• Tetropium fuscum has been introduced and is established in southeastern Canada and can be distinguished from T. castaneum by the thin antenna and the wide band at the base of the elytra, which is not present in T. castaneum. Tetropium fuscum prefers spruce hosts.
• Tetropium gabrieli can be differentiated from T. castaneum by the lack of the lengthwise groove between the base of the antennae, which is present in T. castaneum. Its coloration varies and can look very similar in color to some T. castaneum, but it typically has a black thorax and reddish legs. Tetropium gabrieli prefers larch hosts.

(See the Pest Datasheet for images)