Pine Wilt in Colorado

We love our evergreens here in Colorado — they provide our landscape with year-long beauty. Over the past few years, we’ve been monitoring a new threat to one of our favorite evergreens, the pine tree. Find out the symptoms and how you can protect your pine tree against pine wilt in Colorado.

Pine Wilt in Colorado

What is Pine Wilt?
Pine wilt is a fatal disease, which attacks Austrian and Scotch pine trees. The disease is caused by a microscopic worm (the pinewood nematode), which quickly multiplies in the water conducting tissues of the tree – eventually clogging vessels and causing it to die.


What are the symptoms of pine wilt?
Early symptoms of pine wilt may include reduced shoot growth, needle length and bud development. Pines turn off color (dull green) in August – October. Symptoms are often expressed in early summer, but can occur throughout the growing season. Beginning in late July into August, symptoms first appear on one or a few branches but often develop quickly throughout the crown (top of the tree). The tree may turn from green to brown seemingly overnight, with trees dying quickly in one to two months. The straw colored needles will stay on the tree and recently killed tree branches become dry and brittle.

How do I protect my pine tree?
Healthy pine trees should be protected — the control method is a nematicide injected directly into the tree trunk. Injections are done in the fall or early to mid-spring. Trees must be trunk-injected once every other year for protection. The injections are 80 to 90 percent effective in preventing pine wilt disease in healthy pine trees.
What do I do if pine wilt infects my pine tree? pine wilt in Colorado

Diseased trees must be removed by May to prevent nematode spread and it’s important to hire a professional tree removal company in Denver. The entire tree, including the stump, should be removed. Do not keep Scotch or Austrian pine wood for firewood.

Do you have pine trees you would like to protect? Do you know what type of pine trees you have? Swingle can help. Schedule a free consultation with your local Landscape Care Consultant and get answers to your questions.