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Pinewood Nematode & Pine Wilt

Pinewood Nematode is a variety of tiny roundworm affecting mostly exotic/non-native pines. This nematode is introduced to trees via a carrier beetle feeding on small outlying branches. Once the nematode is introduced, it begins to feed on the tree leading to what is referred to as "Pine Wilt Disease".

What is Pinewood Nematode?

Pinewood Nematode (Bursaphelenchus xylophilus) is a very small nematode (or roundworm) which is known to kill many exotic or non-native pines. First detected in 1979, the nematode is responsible for the Pine wilt disease, and is found in the central US as far north as South Dakota. One of the more commonly affected trees, P.Sylvestris or Scotch Pine, is a good example of a tree that could be affected by Pinewood Nematode.

On the left is a healthy Scot's Pine, and next to it on the right is one affected by Pine Wilt Disease




Why is Pinewood Nematode/Pine Wilt Disease an issue?

  • Pinewood Nematode is capable of widespread destruction of non-native pine plantings, notably Scot's Pine (also known as Scotch Pine), and Austrian Pine.
  • Scot's Pine is a fairly common planting in the Midwest, meaning that there is a large potential for damage.
  • There is no remedy for Pinewood Nematode or Pine Wilt disease, and dead trees are a source of both the Pinewood Nematode, and Pine Sawyer beetles - the most common carrier of the Pinewood Nematode.
  • Once a tree is infected it should be removed and disposed of appropriately to prevent spread of the disease.

How does Pinewood Nematode Spread?

Pinewood Nematode has a unique relationship with a group of insects from the genus Monochamus. These beetles you may commonly know as Sawyers, or Sawyer beetles. They are a group of longhorn beetles which are found in many places around the globe. These beetles are attracted to recently dead or dying trees for breeding, and they lay eggs underneath the bark. The larva then feeds there for 1-2 months, during which time the dormant larvae of the Pinewood Nematode are able to invade the insect through the thoracic spiracles (part of the insect's respiratory tract) and then stay dormant in the beetle's tracheae. After maturation, the adult emerges from the dead tree, now infested with Pinewood Nematode. The larva carried by the insect will then be transmitted by the insects feeding on a new tree, at which point the process may begin again.



More information on Pinewood Nematode, how it is spread, and how it is regulated can be found here:
The Pinewood Nematode: Regulation and Mitigation
Pine Wood Nematode | Diseases of Forest and Shade Trees (umn.edu)
Sawyer Beetles and Pine Wilt Disease (sdstate.edu)


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