Mugo pine losing needles - Ask Extension
Hello,
We live in Lakeview Oregon and planted four 15 yr old mugo pines - pinus mugo fastigiata - last year. One is losing needles (browning) from th...
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Mugo pine losing needles #811860
Asked September 22, 2022, 5:10 PM EDT
Hello,
We live in Lakeview Oregon and planted four 15 yr old mugo pines - pinus mugo fastigiata - last year. One is losing needles (browning) from the center trunk out, the others are showing a few branches with the same issue. The browning started this spring. We did have an issue this year with pine sawyer beetles (google image search of this bug), and didn't realize they could be susceptible to pine wilt, so we didn't pre treat with a systemic. All trees were planted in area that we felt provided a well drained area for their roots, and were watered per the instructions of the grower since planting. Two questions -
1) is this possible pine wilt (due to the parasite of the pine sawyer beetle or some other issue that possibly an arborist would need to see?
2) how can we save our mugo pines, including insecticides? (they are not near a water source, but preferably one that doesn't harm birds}.
I've attached some pictures that might help.
Many thanks,
Mary Dax
Lake County Oregon
Expert Response
Hi and thanks for using Ask Extension! I'm sorry you're having trouble with your Mugo pines.
It's possible that you are dealing with Pine Sawyers and pine wilt, but we don't have enough information to determine that for sure at this point. Pine Sawyers only attack trees that are dead, cut, or in serious decline. That doesn't seem to quite fit your situation.
Pine Sawyers are very common here in our part of Oregon- so finding one on your tree could mean it was infested with larvae, but again it's dead or diseased trees they are typically attracted to. In addition, your picture shows a male, so no egg laying there.
On your picture of the trunk, I can't make out whether any of the spots are actual exit holes from the pine Sawyer. If your tree(s) had exit holes or frass deposits, you could know for sure. It's likely too late in the year for frass deposits (pic here: https://www.ipmimages.org/browse/detail.cfm?imgnum=1643796) but exit holes should still be visible (picture from a similar species here: https://www.ipmimages.org/browse/detail.cfm?imgnum=2131017 ) .
Another way to possibly find conclusive evidence would be to cut off a branch that is affected by the symptoms and look for the blue stain that is characteristic of pine wilt (https://www.ipmimages.org/browse/detail.cfm?imgnum=1541761 or https://www.ipmimages.org/browse/detail.cfm?imgnum=1436064) . This would be a clear indicator that your suspicion is correct.
Overall, and especially depending on when you planted the trees last year (spring vs fall?) Pine sawyer / pine wilt doesn't quite line up. If you don't find one of the "evidence" items above, I'd suggest you take a close look at the browned and affected needles. Are they uniformly brown all over, or do they have any patterns on the needles ? For example, Dothistroma needle blight is found on both native and exotic pines in the US and often starts from the inner needles (see here: https://www.ipmimages.org/browse/detail.cfm?imgnum=1241609) . Up close, the needles have a "red banded" pattern to them before they completely brown out. Other pine needle diseases may have other patterns. Taking a close look at the needles will yield more info.
I hope this is helpful though I was not able to determine the specific problem at this time. I would be happy to take a look at additional pictures - exit holes, up close of needles, up close of the base of needles where they emerge from the stem. Let me know how we can help further after you've taken another look. Have a great day, Nicole
It's possible that you are dealing with Pine Sawyers and pine wilt, but we don't have enough information to determine that for sure at this point. Pine Sawyers only attack trees that are dead, cut, or in serious decline. That doesn't seem to quite fit your situation.
Pine Sawyers are very common here in our part of Oregon- so finding one on your tree could mean it was infested with larvae, but again it's dead or diseased trees they are typically attracted to. In addition, your picture shows a male, so no egg laying there.
On your picture of the trunk, I can't make out whether any of the spots are actual exit holes from the pine Sawyer. If your tree(s) had exit holes or frass deposits, you could know for sure. It's likely too late in the year for frass deposits (pic here: https://www.ipmimages.org/browse/detail.cfm?imgnum=1643796) but exit holes should still be visible (picture from a similar species here: https://www.ipmimages.org/browse/detail.cfm?imgnum=2131017 ) .
Another way to possibly find conclusive evidence would be to cut off a branch that is affected by the symptoms and look for the blue stain that is characteristic of pine wilt (https://www.ipmimages.org/browse/detail.cfm?imgnum=1541761 or https://www.ipmimages.org/browse/detail.cfm?imgnum=1436064) . This would be a clear indicator that your suspicion is correct.
Overall, and especially depending on when you planted the trees last year (spring vs fall?) Pine sawyer / pine wilt doesn't quite line up. If you don't find one of the "evidence" items above, I'd suggest you take a close look at the browned and affected needles. Are they uniformly brown all over, or do they have any patterns on the needles ? For example, Dothistroma needle blight is found on both native and exotic pines in the US and often starts from the inner needles (see here: https://www.ipmimages.org/browse/detail.cfm?imgnum=1241609) . Up close, the needles have a "red banded" pattern to them before they completely brown out. Other pine needle diseases may have other patterns. Taking a close look at the needles will yield more info.
I hope this is helpful though I was not able to determine the specific problem at this time. I would be happy to take a look at additional pictures - exit holes, up close of needles, up close of the base of needles where they emerge from the stem. Let me know how we can help further after you've taken another look. Have a great day, Nicole
Hi Nicole
Thank you so much for your time and diagnoses! We planted these trees last Fall. Because they were newly planted we didn't prune them, so they have sparse areas at the bottom. I'm attaching pictures which I hope are helpful. I didn't consider a fungus!
Appreciate your continued review!
Mary
Hi Mary, hope you are well.
I have a few questions and observations.
1- where is the log/ branch from that is cut off where you are showing me the cross section in your picture? I can't see in the picture of the 3 trees, where this branch would have come from.
2- when you link all the pictures together into one collage, unfortunately it limits my ability to enlarge the pictures to see the details I need to see to have any hope of doing a diagnosis with pictures. When the pictures are all lumped together in the collage like that, when I enlarge them, all the resolution is lost.
3- Would you be able to bring the cut log / branch and some needles into the office at Lakeview? I may be able to work with one of my colleagues there to help you out better.
4- I'm sorry to point this out, but those trees are planted way too close to the house. They are likely to always struggle so close to the building regardless of what we are able to determine is going on now.
thanks, I will be on the lookout for either separated pics that I can enlarge, or to hear that you might be able to take in some physical samples. My office number is<personal data hidden>, I would love to walk you through getting a good sample before you make the drive.
thanks, Nicole
I have a few questions and observations.
1- where is the log/ branch from that is cut off where you are showing me the cross section in your picture? I can't see in the picture of the 3 trees, where this branch would have come from.
2- when you link all the pictures together into one collage, unfortunately it limits my ability to enlarge the pictures to see the details I need to see to have any hope of doing a diagnosis with pictures. When the pictures are all lumped together in the collage like that, when I enlarge them, all the resolution is lost.
3- Would you be able to bring the cut log / branch and some needles into the office at Lakeview? I may be able to work with one of my colleagues there to help you out better.
4- I'm sorry to point this out, but those trees are planted way too close to the house. They are likely to always struggle so close to the building regardless of what we are able to determine is going on now.
thanks, I will be on the lookout for either separated pics that I can enlarge, or to hear that you might be able to take in some physical samples. My office number is<personal data hidden>, I would love to walk you through getting a good sample before you make the drive.
thanks, Nicole
Hi Nicole,
I left a voice mail for you today (9/26/22) - and am sending better pictures (I hope). I would be happy to bring the branch took (see picture of where I removed it), or samples - and visit the local extension service office - whichever you prefer.
I so appreciate you help with this - we had mugo pines in Creswell and they did really well - maybe not the best choice for the high desert.
Thank you,
Mary
Hi Mary, thanks so much for getting samples to our Lake County office so I could take a closer look.
Your trees appear to have a type of fungal disease generally known as a needle cast. There are several types that occur in Oregon. It won't be possible to determine exactly which needle cast is present without diagnostic testing. If you want to take that route, the intake form is here: https://bpp.oregonstate.edu/sites/agscid7/files/bpp/attachments/2020c_plant_disease_form_new_feesaddress.pdf and the base cost is $87.
Most types of needle casts don't require treatment and vary in severity from one season to the next. One type of needlecast, known as Elytroderma, does stay in the tree from year to year and become systemic. Here's some info on that problem: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5342694.pdf
Not every symptom of Elytroderma lines up for your plants- for instance, I don't see any evidence of the dense growth known as brooms. This growth is usually associated with really wet springs, or appear several years after infection- so it's not surprising if we don't see that. Some things that do line up with Elytroderma are the resin deposits in the twigs, visible under the microscope, and the patterns of black stripes on the needles, also visible under the scope. Your issue does appear to be systemic, meaning it is spreading throughout the tree. This is evidenced by the fungal staining in the branch cross section, which you already noticed.
As the PNW handbook points out, https://pnwhandbooks.org/plantdisease/host-disease/pine-pinus-spp-elytroderma-needle-cast
The needle casts are easy to confuse with each other. There are not chemical treatments listed for Elytroderma, but other needle casts may be helped by chemical treatments. Here's a link to info about all of the needle casts listed in the PNW handbook for plant disease management: https://pnwhandbooks.org/search/site/needle%20cast My recommendation would be to continue to nurture your trees, and see how they fare in the coming year. Don't water the needles or canopy of the tree: apply water directly to the root zone. If it becomes necessary to prune, sanitize your pruners between each cut to avoid spreading problems further.
I hope this is helpful, thanks again for bringing your samples in to the office so we could better help you. Have a great day, Nicole
Your trees appear to have a type of fungal disease generally known as a needle cast. There are several types that occur in Oregon. It won't be possible to determine exactly which needle cast is present without diagnostic testing. If you want to take that route, the intake form is here: https://bpp.oregonstate.edu/sites/agscid7/files/bpp/attachments/2020c_plant_disease_form_new_feesaddress.pdf and the base cost is $87.
Most types of needle casts don't require treatment and vary in severity from one season to the next. One type of needlecast, known as Elytroderma, does stay in the tree from year to year and become systemic. Here's some info on that problem: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5342694.pdf
Not every symptom of Elytroderma lines up for your plants- for instance, I don't see any evidence of the dense growth known as brooms. This growth is usually associated with really wet springs, or appear several years after infection- so it's not surprising if we don't see that. Some things that do line up with Elytroderma are the resin deposits in the twigs, visible under the microscope, and the patterns of black stripes on the needles, also visible under the scope. Your issue does appear to be systemic, meaning it is spreading throughout the tree. This is evidenced by the fungal staining in the branch cross section, which you already noticed.
As the PNW handbook points out, https://pnwhandbooks.org/plantdisease/host-disease/pine-pinus-spp-elytroderma-needle-cast
The needle casts are easy to confuse with each other. There are not chemical treatments listed for Elytroderma, but other needle casts may be helped by chemical treatments. Here's a link to info about all of the needle casts listed in the PNW handbook for plant disease management: https://pnwhandbooks.org/search/site/needle%20cast My recommendation would be to continue to nurture your trees, and see how they fare in the coming year. Don't water the needles or canopy of the tree: apply water directly to the root zone. If it becomes necessary to prune, sanitize your pruners between each cut to avoid spreading problems further.
I hope this is helpful, thanks again for bringing your samples in to the office so we could better help you. Have a great day, Nicole
Hi Nicole,
Thank you so much for your time and expertise! I'll make a decision regarding specimen testing after reviewing the links you attached - it would be great to find some kind of treatment if the fungus can be controlled chemically - so that looks like a great idea. We have been watering the trees' needles - so inadvertently may have contributed to the fungus. Hopefully we can save our trees.
I really can't thank you enough for your help.
Mary Dax
Hi Nicole
Can you tell me if our specimens arrived? I sent them to the address in the link you sent, by priority mail, and supposedly they were delivered. Just want make sure.
Thank you
Mary Dax
Hi Mary, I will check on that for you. For most samples it takes time to grow out the culture that leads to identification- that may be why you haven't heard anything yet. I will be in touch.
thanks, Nicole
thanks, Nicole
Thank you Nicole! I appreciate your help.
Mary
HI Mary, I just wanted to let you know I have not forgotten you, I have not heard from the lab. Have a great day, Nicole
Great, thank you so much!
Hi Nicole
Appreciate your follow up. The tree that is most affected has mostly dead needles now. We were hoping to save it. The others appear to have stopped losing needles, but we're cautiously optimistic.
We did put a liquid fungicide on all the trees (Bioadvanced Tree and Shrub Protect and Feed) about 2 months ago.
Hopefully we'll have a diagnosis soon.
Thank you
Mary
Mary, I'm so sorry the trees are continuing to struggle. I'm looking forward to a diagnosis too, since I could not figure it out- I always want to know so I can help better in the future. I'll check in at the plant clinic again at the end of the week if you have not heard anything by then. Thanks for your patience, Nicole
