Callidiellum villosulum

Name:   Callidiellum villosulum
Pest Authorities:  (Fairmaire)
Taxonomic Position:  Insecta: Coleoptera: Cerambycidae
Sub-specific Taxon:  
Pest Type:   Insect
Common Name(s):
   Brown fir longhorned beetle (English)
   Callidium villosulum Fairmaire
Numerical Score:  9
Relative Risk Rating:  Very High Risk
Uncertainty:   Very Uncertain
Uncertainty in this assessment results from: The ability of Callidiellum villosulum to adapt to North American conifers is not known.

Establishment Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Suitable climatic conditions and suitable host material coincide with ports of entry or major destinations.
  • Organism has active, directed host searching capability or is vectored by an organism with directed, host searching capability.
  • Organism has high inoculum potential or high likelihood of reproducing after entry.
Justification: Callidiellum villosulum would find suitable climatic conditions for survival at many North American ports of entry. However, in its native range, its hosts are two genera of conifers not represented in North America. Therefore, its ability to find suitable host trees is questionable.

Spread Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism is capable of dispersing more than several km per year through its own movement or by abiotic factors (such as wind, water or vectors).
  • Organism has demonstrated the ability for redistribution through human-assisted transport.
  • Organism has a high reproductive potential
  • Potential hosts have contiguous distribution.
  • Newly established populations may go undetected for many years due to cryptic nature, concealed activity, slow development of damage symptoms, or misdiagnosis.
  • Eradication techniques are unknown, infeasible, or expected to be ineffective.
Justification: The flight habits of Callidiellum villosulum adults are not known. However, like other Cerambycidae, they are undoubtedly capable of flights of several km. This insect has a demonstrated ability to be easily moved via human assisted transport. It has been intercepted in several states in the Midwestern U.S. on artificial Christmas tree imported from China containing centerposts or bases made from Chinese fir, Cunninghamia lanceolata. Its known host range is narrow and it is not clear if it can adapt to North American host trees.

Economic Potential Is High Risk
The relevant criteria chosen for this organism are:  
  • Organism directly causes tree mortality or predisposes host to mortality by other organisms.
  • Damage by organism causes a decrease in value of the host affected, for instance, by lowering its market price, increasing cost of production, maintenance, or mitigation, or reducing value of property where it is located.
  • Organism may cause loss of markets (domestic or foreign) due to presence and quarantine significant status.
  • No effective control measure exists.
Justification: Provided that this insect is able to adapt to North American conifers, the greatest economic impacts would probably be in Christmas trees plantations and other products that use small diameter material. Plantation forestry would probably be less affected, unless attacks were widespread, because many affected trees would be removed during thinning. Ornamental trees would also be at risk and would experience an increase in mortality and costs associated with the removal and replacement of damaged trees.

Environmental Potential Is Moderate Risk
The relevant criteria chosen for this organism are:  
  • Organism may attack host with small native range.
Justification: This insect infests conifers in the family Taxodiaceae. North American members of this family include redwood, Sequioa sempervirens, giant sequoia, Sequoiadendron giganteum, and bald cypress, Taxodium distichum. These trees tend to be geographically restricted. If they prove to be susceptible to this insect, the unique ecosystems in which they occur could be seriously compromised.

In its natural range, Callidiellum villosulum attacks Chinese fir, Cunninghamia lanceolata (reported as Cunninghamia spp.) and Japanese cedar, Cryptomeria japonica (reported as Cryptomeria fortunei) (Yang Xiu-yuan 1981). Neither of these host genera are indigenous to North America. However these trees are used in some areas as landscape materials.

      Callidiellum villosulum is native to China where it is found in Henan, Jiangsu, Zhejiang and Fujian Provinces (Zhu Chang-qing 1999).
The genus Callidiellum is a small genus of Cerambycidae with representatives in Asia and North America. Two North American species are known; C. cupressi from coastal California and C. viridescens from Arizona. The brown cedar longhorned beetle, C. rufipenne, also native to Asia, has recently become established in several states in the eastern U.S. (Hoebeke 1999).

Callidiellum villosulum has one generation per year in Zhejiang Province (southeastern coastal China). It overwinters as an adult inside the pupal cell, which is located at the end of the larval gallery in the sapwood. By the end of February, the adults become active inside the pupal cell, and chew an exit hole through the wood and bark. In early March, adults begin to emerge. Peak emergence occurs from late March to early April. Adults continue to appear into early May. Upon emergence, adults seek out mates. Mating usually occurs from 8 am to 10 am and multiple matings can occur. Oviposition occurs from mid-March through mid-May. Eggs are laid in the cracks of tree bark. Adults do not feed. Eggs hatch beginning in late March. The young larvae tunnel into the cambium. Larval galleries are rounded on the sides but flattened top to bottom. They are packed with frass and sawdust. In August, the mature larvae tunnel into the sapwood and construct oval-shaped tunnels about 1 cm long. Sometimes these tunnels can be as long as 3-5 cm. In late September, pupation begins and lasts from 10-15 days. In early October, the pupae transform into adults. By late November, the adult blocks the larval gallery with sawdust and overwinters inside the pupal cell. If spring temperatures are low, overwintering adults will suffer high mortality (Anonymous n.d., Zhu Chang-qing et al 1999).

Economic Impact:    The brown fir longhorned beetle is considered a pest of moderate consequences in its natural range, where it infests Chinese fir (Zhu Chang-qing et al. 2000). It usually attacks 3-5 year-old trees, but can also infest the upper branches of mature trees. The larvae feed in the cambium, between the bark and wood, creating irregular oval-shaped galleries that cut off nutrient and water flow within the trunk, and thereby cause tree death. The mature larvae also penetrate into the sapwood, which lowers the both the quality and structural integrity of lumber. This insect can kill trees, but attacks are restricted to small trees or branches of larger trees.

Environmental Impact:   Callidiellum villosulum is not known to have any negative environmental impacts in within its natural range.

Control:    Thorough heat treatment would probably kill larvae within logs. It is not known if successful control measures have been developed for use in a forest setting.

Symptoms:    Boring holes and expelled frass are visible on infested trees. Prior to death, Infested trees exhibit drought-like symptoms.

Morphology:    Adults are 6-12 mm long, chestnut brown color, with the entire body thinly covered with long grayish setae. Head and thorax have shallow punctures and the frons is square-shaped. There is a transverse ridge between the antennae. The antennae are brownish-black. The male antennae are slightly longer than the body, whereas the female antennae are about two-thirds of the body length. The scape of the antennae are coarsely punctured. The prothorax is wider than its length, and the two sides are rounded with no lateral spikes. The prothorax has some hardly visible raised tubercles. The ventral portion of the thorax and the femur of all legs are brownish-red. The femur on all legs is thickened. The basal portion of the elytra are chestnut colored, while the other portion of the elytra is light yellowish-brown and has deeper punctures than those on the thorax. The apical tip of each elytron is rounded.

Eggs are about 1 mm long and creamy colored.

Larvae are about 10 mm long when mature. They are light yellow in color, and the body is slightly flat. The mouthparts are blackish-brown. The pronotum has a pair of brown dots. Thoracic legs are receded. Pupae are 7-10 mm long, oval shaped and cream colored. Antennae are kept close to the sides of the body and bend back near the second pair of thoracic legs (Anonymous n.d.)

Testing Methods for Identification:    Examination of adults by a taxonomist with expertise in the family Cerambycidae is needed for positive identification.

Adults are capable of flight. However, information on whether they are strong fliers and what distances they can travel is not available.

Larvae, pupae and overwintering adults can be transported via international trade in wood products. The primary means of human-assisted transport of this insect to date has been via importation of artificial Christmas trees from China. These trees typically contain stems and bases made of the wood of Chinese fir and contain bark (http//

Anonymous n.d.. Forest insects of China. Translation by: Su Ye , Minnesota Department of Agriculture and Hong Chen, Canadian Food Inspection Agency. (Unpublished Maunuscript).
Hoebeke, E. R. 1999. Japanese cedar longhorned beetle in the eastern United States. USDA Pest Alert. APHIS document 81-35-004. On line:
Yang Xiu-yuan (Editor) 1981. Check list of forest insects of China. China Forest Press
Zhu Chang-qing (editor). 1999. Insect fauna of Henan. Henan Scientific and Technological Publishing House
William M. Ciesla
Name and Address of the First Author:
William M. Ciesla
Forest Health Management International
2248 Shawnee Court
Fort Collins, CO
USA 80525
CREATION DATE:        10/01/99
MODIFICATION DATE:        10/06/99