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Semanotus ligneus

Adult cedar longhorned beetle (native). (Photo: Ophis, Bugguide.)
Scientific Name: 
Semanotus ligneus
Common Name: 
Cedar Longhorned Beetle (Native)
Growing Degree Days (GDD's): 
Not available at this time.
Host Plant(s) Common Name (Scientific Name): 
Arborvitae (Thuja spp.)
False cypress (Chamaecyparis spp.)
Juniper (Juniperus spp.)
Insect Description: 

The native cedar longhorned beetle is found in the northern United States and southern Canada. Lingafelter (2007) notes that adults of this species are active approximately from March through August. Trapping studies have shown adults are attracted to cut logs of Juniperus virginiana for a period of 4 weeks in April in Connecticut (Maier, 2014). Adults have also been observed on the flowers of Pinus spp. and Juniperus spp. (Hammond and Williams, 2013). The larvae of this insect develop in the host plants mentioned above when trees are previously stressed, dying, or dead. As such, this native insect is not considered a primary pest but a secondary invader. Much of the biology and ecology of this species is still not fully understood, including the details of its life cycle. Many reports remain largely anecdotal. In the literature, Semanotus ligneus has been treated as a complex with multiple subspecies, but some authors have elevated the former subspecies to full species status. Activity from our native cedar longhorned beetle may also be confused for that of the Japanese cedar longhorned beetle, Callidiellum rufipenne.

Damage to Host: 

The adults of this insect are attracted to stressed, dead, or dying host plants. The larvae bore into the tree, creating galleries as they feed. Upon emergence, adults leave behind round exit holes. The native cedar longhorned beetle is considered to be a secondary pest and is typically not the primary cause of decline of its host plants.


Look for round exit holes and the presence of adult beetles on stressed or declining trees and shrubs. The damage created by this insect may be confused with that of the others mentioned above.

Cultural Management: 

Maintain tree health and vigor. Proper tree planting and site selection is the best prevention.

Natural Enemies & Biological Control: 

This information is not currently available.

Chemical Management: 

Chemical management of this insect is not recommended because it is a secondary invader and not the primary cause of tree decline.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: January 2024. To check current product registrations in Massachusetts, please visit: .