Pest profile

Japanese Cedar Longhorned Beetle

Callidiellum rufipenne · Coleoptera: Cerambycidae[3]

The Japanese cedar longhorned beetle is a small invasive longhorned beetle whose grubs tunnel under the bark and into the wood of arborvitae, juniper, cypress, Leyland cypress and other cypress-family trees.[1][2]

Female Japanese cedar longhorned beetle with reddish-brown wing covers and long antennae
Female Japanese cedar longhorned beetle with reddish-brown wing covers and long antennae. Photo: Kōsuke Onoda, public domain (CC0), via iNaturalist

How to identify it

  • Adults are small longhorned beetles, about 1/4 to 5/8 inch long.[1][2]
  • Males are shiny blue-black with antennae slightly longer than the body; females have reddish-brown wing covers and shorter antennae.[1][2]
  • Grubs are pale, slender and legless; young grubs pack tunnels under the bark with dark frass, and adults leave oval exit holes.[1]

Where it lives

It was first detected in the United States in Washington State in 1954; NC State and UMass Extension both cover it as a pest of cypress-family trees.[1][2]

US map: public records from 7 states since 1990 (GBIF).

Biology and life cycle

There is one generation a year; adults overwinter in the tree and chew out through the bark in early spring.[1][2]

Females live about 20 days and lay eggs in bark crevices, starting one to three days after emerging.[1]

Larvae feed under the bark, then bore into the wood to pupate.[1]

Damage and signs

  • Hosts include arborvitae, Atlantic white cedar and other Chamaecyparis, junipers including eastern redcedar, Leyland and Monterey cypress, and Japanese cedar (Cryptomeria).[1][2]

Health risk

None to people or pets.[1][2]

Control

Prevention

Pyrethroids are very toxic to fish, so keep them away from pools, ponds and streams.[1]

Pesticides

Spraying infested trees is unlikely to kill grubs inside; to prevent new attacks, NC State suggests a pyrethroid on cypress-family plants in early March and again in early April.[1]

Common questions

What is boring into my arborvitae?
One possibility is the Japanese cedar longhorned beetle, whose grubs tunnel under the bark of cypress-family trees.[1][2]
Can I spray to kill the grubs?
Not reliably; grubs inside packed tunnels are protected, so sprays are used to prevent new egg laying in spring.[1]
When are the beetles active?
Adults chew out of trees in early spring and live only about three weeks.[1]

Sources

  1. NC State Extension, “Japanese Cedar Longhorned Beetle (PDIC Factsheet).” content.ces.ncsu.edu/japanese-cedar-longhorned-beetle (accessed 2026-10-15)
  2. UMass Extension Landscape, Nursery and Urban Forestry Program (Landscape Insect & Mite Guide), “Callidiellum rufipenne (Japanese Cedar Longhorned Beetle).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/callidiellum-rufipenne (accessed 2026-10-15)
  3. iNaturalist, “Callidiellum rufipenne taxon page (order and family).” www.inaturalist.org/taxa/447560 (accessed 2026-10-06)

Updated 2026-10-15. Built from sourced records. Spot an error? Tell us.