Beetles/worms in our ponderosa pines

Asked August 21, 2015, 7:19 PM EDT

We have noticed some of our ponderosa trees have worm like creatures burrowing into them (pine beetle larva??). We just had 5 trees cut down. While splitting the wood we found these worms under the bark. Then we noticed a few of our live trees have a lot of activity in them. How do we kill these things before they kill our trees??

Deschutes County Oregon insect issues tree health

4 Responses

Thanks for the question, a good one.

There are two groups of beetles that are found in ponderosa pine. Bark beetles can attack and kill green standing trees, wood borers (the larvae in the picture which is a roundheaded wood borer- there are also flatheaded wood borers) do not typically kill trees but infest the tree after it is either dead from other causes or very, very weak. Wood borers lay eggs on the outside of the bark and when the eggs hatch the larvae mine through the bark then feed in the cambium layer for some time and eventually bore into the wood itself. Bark beetle adults bore through the bark and lay eggs between the bark and wood where the larvae feed and develop into adults to then leave the tree to find a new host. They do not tunnel into the wood. They kill the tree by girdling as well as introducing a blue stain fungus that clogs the water conducting tissue (sapwood).

It typically takes about a year from the time bark beetles enter the tree and lay eggs and you see the needles turn brown (this however does vary). In most cases the trees are attacked in the early summer to fall and it takes beetles to about a year to develop from an egg to adult (this also varies some). The point being that if you see needles turning brown to red, the beetles are in the tree and there is nothing that can be done to save the tree.

The wood borers you found in the firewood probably did not kill the tree, either bark beetles did or something else, so no need to control wood borers. They do not typically infest sawn lumber. The activity you mention on your green trees, I am not sure what this means but if you find pitch tubes (many) on the outside bole of the tree (main stem), boring dust in cracks and crevices on the bark or at the base of the tree then you could have bark beetles attacking the tree. The only real way to tell is if you take a little bark off and examine the area between the bark and wood (cambium area), if it is dark brown or black and/or if you find beetle adults (1/8-1/4 inches in length) or larvae then the tree is infested. If it is then there is nothing you can do to save the tree. The only way to help a green tree is if you prevent the beetles from entering.

There are two main ways to protect the tree. From your note i am not sure if this is a landscape situation or you own some forestland. If forestland or a stand of trees (or a clump of trees in your yard), the most practical approach s to make sure the trees are spaced appropriately, the larger the tree the more space it needs (talk to an ODF Stewardship forester or your local Extension Forester, but generally a spacing using the following guide works pretty well: determine the average stand Diameter at Breast Height (4.5 ft above the ground) + 6 to 8 ft is in the ball park. So if the average tree DBH is 12 inches the spacing would be 18-20 ft between trees (12 +6-8 = 18-20 ft).

For high value trees in the forest or around your home, your other option would be to use an insecticide (Carbaryl) as a preventive application applied before bark beetle flight (June). Follow label directions. This will need to be applied annually or at least ever two years and needs to cover as far up the tree bole as possible, at least to 30 ft. Anti-aggragating pheromones are also now available for Mt. pine beetle (only if this is the species threatening your pines), however this method is not always effective and requires a professional arborist or entomologist to provide guidance on how to use them effectively.

You can go to this link for more information about bark beetles and wood borers: http://www.oregon.gov/odf/privateforests/pages/fhpests.aspx.

If you have bark beetles attacking your live trees it is likely because the trees are experiencing some type of stress, which can be from a variety of causes, including overstocking (need to thin), root disease, root damage, soil compaction, tree injury, drought and others. Bark beetles usually are not the problem, it is some other underlying stress factor or factors.

Hope this helps. Contact your local OSU Extension Forester (Nicole Strong in Deschutes County) or ODF Stewardship Forester for more information.

Thanks for the information. It is very helpful. Attached is a picture of the live trees that are damaged. Is this caused by the bark beetles as noted in your response or the wood borer? Still concerned that this could kill the trees. We didn't have any issues before we thinned a few trees.

Thank you for your time!
Debbie

Thanks for the information. It is very helpful. Attached is a picture of the live trees that are damaged. Is this caused by the bark beetles as noted in your response or the wood borer? Still concerned that this could kill the trees. We didn't have any issues before we thinned a few trees.

Thank you for your time!
Debbie

If these pitch tubes are only at the base of the tree then most likely this is the red turpentine beetle. It is the largest bark beetle species we have and it typically only attacks the lower few feet of a pine and generally does not kill trees. However, it can weaken the tree and other bark beetles can come in and sort of finish the tree off. Once the turpentine beetles are in the tree not much you can do but keep tree as vigorous as possible with deep watering. If you have only a few trees i would suggest spraying the base next spring with carbaryl to keep and future beetles from boring into the tree. The red turpentine beetle causes larger pitch tubes than the mountain pine beetle and like i said only attacks the base of the tree. If these pitch tubes are up farther on the bole, i.e. 20 to 30 ft or more, then this is the mountain pine beetle and if the entire circumference of the bole is affected there is a good chance the tree is dead. However, sometimes the tree can pitch the beetles out, so have to wait to see what happens or cut into the bark to see if it is healthy tissue or not.

These pitch tubes on the bark are not wood borers.

Hope this helps...