Japanese Pine Sawyer

**This organism is not known to be present in the United States but poses a threat. Pine sawyers or pine sawyer beetles are longhorned beetles in the large genus Monochamus (about 150 species).  All, including M. alternatus, are secondary pests of conifers, breeding in dying or weakened trees. All species are potential vectors of pinewood nematode, which is transmitted from tree to tree via adult feeding on pine shoots. 

Native Monochamus spp. are considered beneficial decomposers of conifers because they rarely kill the trees they feed on. This is not the case for Monochamus alternatus, the Japanese pine sawyer or other exotic species. This species is considered potentially invasive and a pest of economic importance.  


Japanese pine sawyer is a major vector for pinewood nematode which causes pine wilt disease. This particular nematode is native to North America but was introduced to Asia some time ago. In 1979, the combined activity of M. alternatus and this introduced nematode resulted in a record loss of 2.4 million cubic meters of timber in Japan. (CABI, 2014)

If M. alternatus was introduced to the US, could it bring with it exotic nematodes? It has been reported that the Japanese pine sawyer also vectors other species of nematode that are not known to be in North America.


Exclusion is the first line of defense however because the insect spends most of its life concealed inside trees, it could be introduced unknowingly. The likely pathway for introduction would be through solid wood packing materials. Eggs, larvae and pupae can be transported in unprocessed logs, wood crating, pallets and dunnage.

If introduced, adult beetles fly and are capable of dispersing on their own. Adults are attracted to recently diseased trees and fresh logs.




Japanese pine sawyer feeds mainly on pine species. In Japan, the preferred host is Pinus densiflora and in China, the preferred host is Pinus massoniana. Minor hosts include other plants in the Pinaceae family.


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.