Japanese Pine Sawyer

**This organism is not known to be present in the United States but poses a threat. The Japanese pine sawyer (JPS), Monochamus alternatus, is not known to be present in the United States but may pose a serious threat to our urban and forest ecosystems if introduced. Like other beetles in the genus Monochamus, Japanese pine sawyers breed in dying or weakened trees. In their native regions, these insects have historically been considered beneficial decomposers, but they could potentially be invasive pests of economic importance if introduced into the U.S. In Asia, JPS is a vector of the pinewood nematode, which causes fatal pine wilt disease.


In 1979, Japan lost 2.4 million cubic meters of timber to pine wilt. Although the pinewood nematode is native to the U.S., it has not caused such devastation in the States. Native trees have historically been immune to the disease, leaving only exotic species susceptible to pine wilt. However, it is unknown whether introduction of Japanese pine sawyer to the U.S. could alter the nematode’s range and disrupt the current balance. A resulting mass loss of pine trees would harm the timber industry; result in domestic and international trade quarantines; and inflict wider ecological damage.


Japanese pine sawyers could be introduced to the U.S. through solid wood packing materials not properly heat-treated to kill pests. These materials include wood crates, pallets, and other wood packaging used to transport goods. JPS spend much of its life cycle concealed inside wood. If infested wood is used to create these materials, the materials could contain life stages of the insect that inspectors could unknowingly overlook during an inspection. If introduced, these beetles could disperse and adults are capable of traveling up to 20 miles in search of hosts.


While pine species are the primary host for the Japanese pine sawyer, JPS has also been known to feed on larch, cedar, fir, and spruce. In Japan, the preferred host is Pinus densiflora and in China, the preferred host is Pinus massoniana.


Japanese pine sawyers spend much of their life cycle—both the larval and pupal stages—hidden within the trunks of pines, so they can be difficult to detect early in an infestation. The most noticeable signs of Japanese pine sawyer include:

  • Adults feeding on twigs
  • Egg deposit sites in the bark of host trees
  • ~9mm (0.35 inch) diameter round to oval exit holes
  • S-shaped and vertical larval tunnels filled with wood shavings

It can be difficult to differentiate between the Japanese pine sawyer and visually similar beetles present in the U.S. If you see an insect with the following traits, please rapidly report its presence:

  • Longhorned beetles between 0.5 and 1.1 inches in length
  • Long antennae 1.3 to 2x as long as the body
  • Mottled brown coloration with white patches overlaid with orange stripes
  • Protective forewings meet in a straight line down back
  • Dense patch of short, mud-yellow hairs at base of wings, where thorax meets abdomen

If you observe the following tree symptoms examine more closely for signs of a beetle infestation:

  • Unexplained wilting
  • Dying branches, dead branches, rapid tree death
  • Change in needle color from green to yellow to red


Think you've spotted this pest?

If you think you've found this pest in your landscape contact your local extension office to see about sending in a sample.
Find your local extension office here.