Hort Q&A: The problem with pine trees

Carla Smith, horticulture educator
Pottawatomie County Extension Service
Pine trees

What is wrong with our pine trees?

Pines have had a hard year, and now we are seeing another problems developing. Many pines suffered from the bitter cold in February, especially those suited to southern areas. Some pines do very well in our zone, cold hardiness zone 7. Unfortunately, in February, we were at zone 5 temperatures for over a week. Pines like slash pine, spruce pine, and longleaf pine are zoned for zone 7. Shortleaf, loblolly, and Japanese black, cluster pine are in zone 6, and ponderosa is zone 5. More ornamental landscape varieties, Austrian - zone 4 and mugo – zone 3. That’s lots of numbers, but the take away is that some can tolerate the cold much better than others. Specific site and location made a big difference on how well they survived. Generally, if a pine turns brown, it is finished. This year we did see some that had needles brown out with the freeze that have re-leafed in following weeks and are recovering. ‘Wait and see’ has been our approach for the recovery from the cold weather event, as we haven’t experienced cold like this before.

Pine borers are another common question. Borers tend to attack stressed tress, so keep an eye out for this. The ice storm in October, followed by the February cold spell did create some plant stress. We had good rainfall earlier in the year which was helpful. Deep water trees once every two to three weeks in the summer if we do not have regular rainfall. If the holes in the tree are ‘shotgun’ pattern, or very randomly scattered, borers are probably the culprit. If the holes are very organized in straight horizontal rows, that is woodpecker damage. Our fact sheet on woodborers has some good information and photos: https://extension.okstate.edu/fact-sheets/woodborers.html

Pine wilt cases are showing up now. This issue happens very quickly. Trees may appear normal and be gone in a matter of days. Our OSU Fact Sheet on Pine Wilt Disease is a good source for information. https://extension.okstate.edu/fact.../pine-wilt-disease.html

Pinewood Sampling is another resource: https://extension.okstate.edu/.../sampling-for-pinewood...

This disease involves the Pine Sawyer Beetle and a Pinewood nematode. Once the nematode is inside the tree, there isn't anything that we can do. Controlling the Pine Sawyer Beetle may help, as it transports the nematode. See fact sheet above for all the details.

The photos below are from one of our recent clients. As heartbreaking as it is to lose these trees, we can use this to pass on the information. Note the blue staining in the wood in the photos, this is seen in dead and dying pines.

If a pine had died due to borers or disease, it is important to go ahead and remove those from the property. Taking them down will reduce the insect activity and help reduce the spread to other pines.

Pine trees are near and dear to my heart. As a young FFA student, I helped my dad plant pines trees from the Oklahoma Forestry Department on our family place in Bethel. All bare root seedlings, some no larger than a pencil. We watched them grow over the years and they are a beautiful sight. These were mostly loblolly, with a few scotch, ponderosa, and short needle pines. The loblolly seemed to do the best, or that is what we planted in larger quantity. Even if it is just one tree that you are used to seeing on your place, it’s hard to lose part of our landscape. Much like with people, reduce stress and feed or fertilize appropriately. For trees, don’t over water your pines, and water deeply when necessary. Pines are rather self-mulching as they will shed needles under the tree. Leaving some pine needles for mulch works great! Feel free to contact our office with questions. This is county fair week, so I will be hard to catch by phone. You can email me at carlasm@okstate.edu or catch me out at the fair. I’ll return your email the following week. The Master Gardeners will have some copies of the OSU Pine Wilt Fact Sheet at their booth in the commercial area of the fair or you can access this with the link provided. Come by and visit!