Japanese Pine Sawyer

**This organism is not known to be present in the United States but could pose a threat if introduced. The Japanese pine sawyer, Monochamus alternatus, is a longhorned beetle native to Asia. Like other beetles in this 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.


Japanese pine sawyer is a major vector for pinewood nematode, which causes fatal pine wilt disease. In 1979, this disease cost Japan a record loss of 2.4 million cubic meters of timber. Although the pinewood nematode is native to the U.S., similarly devastating impacts have not occurred 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 could alter the disease’s range and disrupt its current balance. Mass loss of pine trees would harm the timber industry; result in domestic and international trade quarantines; and cause wider ecological damage.


Japanese pine sawyers could be introduced to the U.S. through solid wood packing materials including wood crates, pallets, and dunnage. Since the insect spends much of its life cycle concealed inside a tree, it could be unknowingly overlooked.

If introduced, these beetles could disperse naturally by flying. Adults are capable of traveling up to 20 miles in search of hosts.


As adults feed upon the twigs of healthy pines, beetles which have contracted the pinewood nematode can spread it to uninfected trees. Within weeks to months of introduction, the tiny roundworm disrupts the water transport systems within trees, causing rapid decline and fatality.

While pine species are the primary food source for the Japanese pine sawyer, it 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.


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.