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Diseases of Pine Trees

June 4, 2018

Written by Dave G.

Planting a tree is an action full of hope. We hope that our tree will grow and flourish, living out its life – which will certainly be decades, and perhaps even a hundred years or more – free of problems that threaten it. This is usually true, trees are remarkably tough, and most grow and survive without problems. But some don’t. Sometimes it is a major outbreak, like Dutch Elm Disease, that decimates a much-loved tree. Most often it is a lower-level disease that picks away at a particular type of tree, like the Verticillium Wilt that is spreading through maple trees these days. Other diseases look dramatic but do very little harm. So for gardeners, it helps to have some knowledge of diseases, to encourage the good, and separate the bad from the merely ugly. An earlier blog on Diseases of Maples has been a popular resource for our readers, so to continue giving that basic information, this time we are going to look at the diseases that pine trees may suffer from, which one’s matter, and what to do about them.

Hey, That Doesn’t Look Good!

Pine trees only have so many ways to tell us they are not doing well, and there are several things we might spot that are indicators of diseases. The main things you might see are:

Resin running down the trunk – If the bark is injured by diseases sticky resin often escapes and flows down the bark. This can even collect at the bottom of the tree, on the ground. As it dries it turns white and flakey around the edges of the flow, or it may dry completely into white or grey flakes on the bark.

Dead shoots or branches – these might be anywhere in the tree – foresters often call them ‘flags’. Notice if they are on new shoots only, before the needles have had time to develop fully, or if a whole branch of mature shoots has died.

Yellow needles – sometimes needles turn yellow, sooner than they normally would. Later they will turn brown, either completely or in bands. This shouldn’t be confused with the normal, season browning and falling of older needles. These will always be the last needles before the bare part of the stem. If they are, nothing is wrong, but if it is younger needles that are yellow, you could have a problem.

Round swellings and growths on the stems – these are called ‘galls’, and although unsightly they are rarely dangerous to the tree. Several different organisms can cause them.

Know Your Tree

You can see there are not a lot of different things that will show you there is a problem, so knowing what the problem actually is depends a lot on what kind of pine tree you have. If you don’t know, ask around your neighbors, often they will know, or take a branch – with some cones if possible – to a local garden center and they may be able to help. There are good resources on the internet too. You need to know how many needles there are in the bundles on the stems, and having a mature cone helps a lot. Deciding on what disease is affecting your tree is a combination of what signs you see and what type of pine it is, since many diseases are specific to one or a few different species.

Some Common Pine Diseases

There are a number of diseases that can be seen on different pines, but these are the most common of the serious ones, that can cause major damage or death.

White Pine Blister Rust

If you live in the north-east, you might have a white pine tree. These lovely native trees are usually easy to grow, but there is one serious disease that can attack them. This fungus attacks side branches, which die – creating ‘flags’ – and then spreads along the branch until it meets the trunk. There a canker forms, and sap runs down the bark. Once the disease reaches the trunk there is nothing that can be done. Over a few years all of the tree above that spot will die. If it happens high in the tree it will in time create a picturesque dead top, for birds of prey to use as lookouts, but if it is lower down most of the tree will be killed – it’s the luck of the draw.

To prevent this disease, keep a close watch on your white pine. If you see small dead branches, remove them, cutting at least a foot further down, into healthy parts. The fungus spreads ahead of the dead sections. If you can make it more than a foot, even better. This will keep the disease away from the trunk, and you will only get minor branch loss.

Diplodia Tip Blight

If you see new shoots dying on your pine tree in spring, and sap oozing from the area where those new shoots develop from, then think about what kind of pine this is. If it is Austrian pine, or Ponderosa Pine, this is probably Diplodia Tip Blight (also known as Sphaeropsis). Give the dead needles a gentle tug, and if they come out easily, that confirms it. Over time more tips will die, killing whole branches, usually lower down on the tree. A badly-infected tree will not have much life left in it. This disease can be controlled by spraying with suitable fungicides (copper sulfate is a suitable organic spray, and propaconazole or thiophanate-methyl are also effective) over a limited period in spring, when the buds are swelling, and again before the needles fully expand. For a larger tree you will probably need to bring in an arborist.

Pine Wilt

This is certainly the most serious pine disease around, because it strikes and kills so quickly that little can be done. This disease is also unusual because it is caused by a microscopic organism called a nematode, and it is carried from tree to tree by beetles. The first sign is a greying of the green color of all or most of the needles, followed by yellowing and then browning.  You may see the signs in spring, and by late summer or fall the tree will be completely dead. If you see browning, but the tree stays alive for months or years, it probably isn’t Pine Wilt. The nematodes have blocked all the water-transport system of the tree, and it dies from lack of water. However, watering it will do no good, because the blockage is inside the tree. There is no cure for this disease, and dead trees should be removed and burned or chipped straight away. It takes a plant laboratory test to confirm this disease, and these are available – check your local university or college. Austrian, Scots, and Japanese Red Pine are the pines most usually affected. Don’t replant pine as a replacement – choose a spruce, fir, or hemlock instead.

 

There are numerous other pine diseases, but they are mostly just unsightly, rather than lethal. Good management, such as not changing soil levels and covering the roots with fresh soil, can go a long way to keeping your pine trees healthy.

Comments 64 comments

  1. April 8, 2019 by Rick Balch

    Hi,
    I think I have a Desert Pine variety here in Mesa Arizona. Bought as a small 1 gallon 6 years ago I put in a 5 gallon and then in the ground 3 years ago…At seven feet it’s green, but just recently (two to three weeks) the newer green needles have been shriveling or curling up to gnarly ends. Internet has no solution. Do you have an idea?
    Thank you, Rick,

    1. April 9, 2019 by Dave G

      Sorry, I am not too familiar with growing in Arizona, so I don’t think I can help much. If there are’gnarly ends’ are you sure they are not being eaten? Shriveling suggests a root problem (dryness? Too wet?), and there are several types of caterpillars and sawflies that feed on pine needles.

  2. May 3, 2019 by Richard

    Hi
    White covering on pine followed by die back

  3. June 5, 2019 by Robert Craig

    Hello
    I have a few 20 foot ponderosa pines in my backyard up here in Canada.
    One of these pines as sap running down it, from what looks like round or oval holes in a circle about 10 feet high.
    Any advice on what is causing this and how I can remedy it?
    Rob

    1. June 10, 2019 by Dave G

      Sounds like woodpecker (sapsucker) damage. Goodle ‘pine and woodpecker; and you can see images.
      If it is this, you can’t really do much about it, but the damages is shallow, and usually heals.

  4. July 23, 2019 by KVH

    Pineus thunbergi needles emerging with severe bends. Appear now like little hooks. Help!
    What type of fungus is this? Recommend treatment?
    Might you email back please?

    1. July 23, 2019 by Dave G

      Sorry, at a loss with this one. Are you sure they are not being eaten down into short stumps, perhaps with some parts of the needle still hanging? Sawfly larvae attack a variety of pines, and eat the needles right down. The best control is daily inspection when new needles are just expanding, and hand picking or shooting off with a jet of water. The pupate in the soil beneath the tree, so after a few years of killing the larvae you will usually get rid of them. If it isn’t that, I have never seen or heard of anything like this.

  5. July 23, 2019 by KVH

    I’d i could send a photo you would see the very tight curls and odd twists

    1. July 24, 2019 by Dave G

      I even looked to see if there was a variety that naturally had twisted needles, but I didn’t find one on the conifer database. Is this all over the tree, or just on a few branches? Is it a large tree you have had for some time? If it is persistent, and the needles don’t drop, you could have a new variety on your hands!

  6. July 24, 2019 by KVH

    Thanks for the return note.
    This is on a few of my pineus thunbergi as bonsai I have had for over 40 years. It is not on all the new growth. The candles as they break open and elongate not all needles show this bent condition. They are not spirally twisted but simply bent. Some are 90and most at 180 and beyond in to a full curl.
    Color is excellent, texture is shiny and the terminal is sharp. The needle is simply mis formed as it emerges from its sheath which in some cases is holding the needle back and causing the bend. Photos can be made if you email me.
    Thanks
    KVH

  7. Could someone put some photos up? I think I could have the nematodes but I’m not positive.

    1. August 15, 2019 by Dave G

      We don’t have the facility to do that, but if you Google it should should find lots of images. Just check they really are of nematodes injury, because all sorts of things get mixed up in Google image searches!

  8. Also I just looked and there are still green needles on the ends of many branches and some branches are bare all the way up to the trunk and the small shoots coming off mains of the larger branches which are coming directly from the trunk are drooping towards the ground and are grey and have a buildup of some kind of whiteish/silvery mold or something.

  9. There is no browning of the needles and they definitely do not look like the wilt pictures. It starts in by the trunk and works it’s way out. There’s a lot of pine cutting going on around our townships here in western New York. Any help would be greatly appreciated.
    Thanks,
    -Lar-

    1. July 31, 2019 by Dave G

      Zimmerman Pine Moth causes a buildup of sawdust and resin at the base of the branches – check some pictures of that.

  10. August 19, 2019 by lloyd crawford

    I have a pine 30 ft. tree , presumeable white pine. as of late it has turned white on some of trunk and larger parts of all limbs. solid white . Information as to probable issue would be helpful.

    1. August 21, 2019 by Dave G

      You have an infestation of an insect called the Pine Bark Adelgid. It is a specialized kind of aphid, that lives underneath that white material you see. You can confirm this by climbing up and brushing your hand across it – it will be sticky and gooey. You might also have sticky deposits underneath the tree, covered in a black powder, called black mold. The mold is completely harmless and will go away if you fix the problem.

      Big infections can kill a tree, but it is easy to control. Find some ‘summer oil’ at your garden center, and spray the infected branches with it. Also get some ‘dormant oil’ and spray again in late winter – spray as much of the tree as you can. You can tell when it is dead because after a while it won’t feel sticky anymore. This is a spreading problem, and you have a pretty impressive example! You can see more here

  11. We have a pine tree (not sure of species but not a blue spruce). There is a lot of white on the bark and some on the branches. It is also leaning. The white is not sticky. We live in north east Illinois.

    1. September 30, 2019 by Dave G

      I suspect you have Pine Bark Adelgid, as in the comments above, to lloyd crawford. Same advice, so see that comment. You might want to check with an arborist to be sure.

  12. October 5, 2019 by iMartin Carney

    Can I send you images of a pine tree that is losing bark and seems to have boring bugs?

  13. October 28, 2019 by Noelle

    Eastern Nebraska here. We’ve lost most of the long needle pines on our acreage, but that’s not my question. My medium length needle pines are now dying…but not in the same manner as the long needle ones (those browned in large patches and then eventually died). The medium-needle trees are yellowing and browning uniformly near the full length of the trunk. I have too many to treat, if there is a treatment, but I would like to know what’s going on. All the short needle pines are doing great….so far. Knock on pine wood.

    1. October 29, 2019 by Dave G

      Without more information, this sounds like long-term stress. Have you had extended drought, or extreme winter cold? I am sure you realize that the internal leaves of pine trees brown naturally before dropping, leaving the outer needles green, so I don’t think that is the problem, although it often causes concern. With a lot of trees there is not much you can do, but I might check with a local forestry officer, if you have any in your region.

  14. November 3, 2019 by Fern Frank

    Have pine trees dying from the inside rotting out. Center is gone and red color. What could be causing this and is there anything I can do? We had a bad storm with high winds which toppled a tree that looked healthy. It snapped towards the bottom and was rotted inside but top branches still have green needles

    1. November 4, 2019 by Dave G

      This is – not surprisingly – called ‘red heart of pine’. It’s a fungal disease and affects mostly older trees. You might have seen ‘mushrooms’ growing on the outside of infected trees – big structures called ‘conks’, or ‘bracket fungus’, that are the fungus reproducing itself. it gets in through broken branches, cuts, or where branches have been removed. Good pruning practices, especially leaving the branch collar in place, help prevent its spread, but there is absolutely nothing you can do once a tree is infected. You should consider planting some new trees, to replace these ones as they go.

  15. February 25, 2020 by Richard Nichols

    We have about 15 pines that died in the past 2 years. The bark started to strip off and every time a storm came through wind and rain would damage them even more. We are left with a disaster area and would like to know the cause of the pine trees deaths.
    Kind regards,
    Richard Nichols
    Ricknichols21@gmail.com
    770-605-0244

    1. February 26, 2020 by Dave G

      Sorry Rick, not enough information here to see what happened. You would need to know the type of pine, and the early signs when they were still alive.

  16. April 15, 2020 by I Tomlin

    I have three pine trees, not sure what kind, that we trimmed in January. A couple of weeks after the trim, the needles on the tips started turning brown. They’re almost fifty years old and were healthy before the trim. The limbs are bare.
    I’m so concerned I don’t want to lose them. Please help.

    1. April 15, 2020 by Dave G

      You cannot trim pine trees. If you cut back below areas where there are green needles on the stem, that stem will simply die. Bare limbs will not re-sprout. I don’t know if you had a professional trim your trees, but it doesn’t sound like it.Also, trimming in the middle of winter was a bad idea.

      With pines, you can shorten new growths back to their base before the needles expand – what is called ‘candling’. That is the only trimming possible.

      All you can do now is wait and see which branches produce new needles, and then trim all the other dead branches back to their trunks, being sure to leave the collar intact. After they re-sprout you will have to assess if they are worth saving. Sorry to give you bad news.

  17. May 4, 2020 by John Langley

    I have several large pines in my front yard. They all look great except I noticed yesterday a yellowing of the pine needles in several spots on the tree, I am concerned that this tree has what we call here in Oklahoma pine needle fungus. I was able to save one tree years ago by cutting off the brown needle branches, but these trees are at lease 60 feet tall. Is there a spray I can purchase to save this tree?

    1. May 4, 2020 by Dave G

      Correct identification is important. You will find these University pieces useful. http://www.forestry.ok.gov/Websites/forestry/Images/Common%20Diseases%20of%20Pine%20Trees,%20OSU.pdf https://www.canr.msu.edu/news/why_are_my_pine_trees_turning_brown. A ‘copper-based fungicide’ mentioned in the Michigan piece would be Bordeaux mixture – copper sulphate and lime, or ready-made lime-sulfur from a garden center, if you can find it. There are recipes online for both. Good luck.

  18. May 8, 2020 by Chris

    Hi. I have a large white pine behind the house. We recently had a patio installed which required some root disturbance. I’m now noticing browning of the tips of some branches. What should I do to ensure the health of the tree? Thanks

    1. May 8, 2020 by Dave G

      Mature pines don’t like root disturbance, especially if soil has been placed over the roots, so they are now deeper. Or if significant amounts of root were cut away. If there has been extra soil added, can you remove it? That would be best -done by hand to avoid further root damage. You can create a tree-well around it to deal with the lower level – that should have been done during construction. If it isn’t that, or you can’t now remove the soil, I suggest a wait and see attitude. Give it three years and then have any dead branches removed. If you have poor soil, feeding the tree could be worthwhile, but probably not vital. Feeding with a root injector, done by a qualified arborist, would be best if you go the fertilizer route, although surface application of a tree food would be OK.

  19. May 10, 2020 by Scott

    I have a pine about twenty ft. You can see slot of stress almost deformed limbs big some areas small almost pencil thin at the end . Mid way up almost too the top the bark is very different in texture . Any ideas…..

  20. May 11, 2020 by Theresa

    I have several acres of pine. Lost numerous a few years ago to pine beetle. Have cleared out all the standing dead. Just noticed a lot of my new growth trees (2-4′ tall) have red needles. It’s frustrating! I’m not sure what to do. Is it a nematode? I live in western Montana at 6500 ft.

  21. May 13, 2020 by Clark

    I live in central Alabama. My pine tree is about 60ft tall. For the past year there has been an excessive amount of pine cones on the tree. It legitimately looks as though there are more pine cones than needles. Is this a sign of any disease?

    1. May 13, 2020 by Dave G

      These ‘distress crops’, as arborists call them, are a sign of severe stress, but of what nature will depend. The cones are probably also undersize? If they are, that would confirm that it is a distress crop, and not just a naturally heavy year. It could be disease, but it could also be perhaps a drought last summer, or the summer before, or flooding?

  22. May 31, 2020 by Bobbi Balchunas

    Good evening,

    I have a large medium needle pine tree and within the last few days the top branches are laying down (toward the ground) needles look fine not brown or gray. I would guess it’s about the top quarter of the tree. Do you know why this is happening?

    Thank you.

    1. June 1, 2020 by Dave G

      Sorry, can’t think of an obvious reason for this, but it sounds like damage to the trunk below those upper branches. Is this a white pine? If so, blister rust can cause that, when the infection of a branch reaches the trunk. No cure, but if you cut off that top section the tree will continue to grow.

  23. June 1, 2020 by Diana Rogers

    We live in Central Oregon and in a forest. We have many small pine trees that have a yellow powder on knots on the trees. Mostly on their trunks. Can you tell what it is and how to kill it?

    1. June 1, 2020 by Dave G

      It might not be harmful. Could it be pollen from the trees that has stuck to the bark? Or a surface fungus on the exposed wood, most of which are harmless. Perhaps you could contact your local forestry department, who would know local conditions better.

  24. June 16, 2020 by David Wiseman

    I have a 30 + year old white pine in New Jersey. the branches have been pruned off about 15′ up the trunk. It appears the collar has been damaged on all the cuts. Most have a white substance draining out and running down the trunk. At one cut there is a 1/4 cup of orange-brown gelatinous material coming out of the pruning cut. Any idea what the problem might be?

    1. June 17, 2020 by Dave G

      It’s a pity it was so badly trimmed! The white material is just sap – the flow will stop once the cuts heal over. The brown material is probably resin, which will harden, and actually helps protect the wounds against infection. Hopefully the tree will be fine in time.

  25. June 19, 2020 by Mary Lou MacCall

    We have long leaf pines in NC. Some of mine are turning green around the bottom and then dirt is washed away. I live on a hill and these are at the bottom along the street. Would this be mold? I am afraid that if we have a hurricane this year they may fall.

    1. June 20, 2020 by Dave G

      It sounds more like moss, which doesn’t hurt the trees, but it does suggest that water is standing in that area, which they won’t like. Maybe the drainage at the bottom of the hill is obstructed. It sounds like you have soil erosion on the slope, too, which could indeed loosen the roots and leave them more liable to wind throw. Perhaps you can put a bark or similar mulch on the slope, and secure it with netting that you peg down? Hard to be sure without seeing the location.

  26. June 21, 2020 by Norma Evans

    I have a twisted needle pine purchased 3 months ago. It jhas a white sticky substance on it. Could you advise as to treatment?
    Thank you

    1. June 22, 2020 by Dave G

      This sounds like sap on the stems. Maybe there was a damaged branch that bled? Probably nothing to worry about – it will harden and disappear in time. If it is on the needles however, or the young stems beneath the needles it could be mealy bug or something similar – spray with neem oil to control it.

  27. June 25, 2020 by Alan K.

    I live in eastern Virginia on the Chesapeake Bay and have a number of old and new pine trees, what variety I don’t know, on my property. Some of the older ones have shed their bark and strong winds have blown away most of their branches. They look dead. A storm blew one over recently and when I was cutting it up I noticed the center was eaten out. The core looked intact, but the wood ringing it had rotted or been eaten away. Any idea what this might be?

    1. June 25, 2020 by Dave G

      Some pines don’t live all that long, so the could simply have died of old age, or ground level changes, which pines are very sensitive too. As for the dead one, it sounds like a fungus or insects had attacked the softer sap wood after it died, but the harder heart wood is more resistant to decay, so it is still intact. Nature has her cycles. . .

  28. June 26, 2020 by A Larson

    I live in Northern Arizona in a forest of Ponderosa Pines at approx 6000 ft in elevation. In the last couple of years, the bark on the shader side of one tree looks like bark is peeling off approx 1/8″ thick. My trees seem to all be healthy and are deep watered in times of drought.
    Any idea if this normal or should I contact a tree person?

    1. June 26, 2020 by Dave G

      Hard to say what that might be. If it runs down the trunk in a long, narrow line it could be a lightning strike. These usually scar over and aren’t a serious problem. If it’s over a wider area and you value the tree it might be worth getting an arborist to take a look.

  29. July 5, 2020 by Kim G.

    It appears that the branches are dying on my pine tree which is around 40 years old. Is there anything I can try to save it?

    1. July 6, 2020 by Dave G

      If these are just lower branches it is completely normal for most pines to develop high crowns and long bare trunks as they age.

  30. July 15, 2020 by Chris Smerecak

    My blue spruce pine trees seem to be dying from the inside towards the outer part of the branches mostly at the bottom part of the trees. Upper branches are still getting new growth but for the most part look like they are dying from the bottom up. They don’t get much sun and are about 15 years old. I also have some that are in full sun and look a little better but seem to be dying mostly around the bottom. Any thoughts?

    1. July 16, 2020 by Dave G

      All small trees lose their lower branches as they grow, and more quickly if they are in low light. You need to trim into conical shapes from an early age to keep those lower branches alive. Once gone the main trunk won’t produce new ones, even if you cut back – almost all conifers can only sprout from branches that have green parts on them. Yew trees are an exception to that. I would clean them up by removing those dead/dying branches at the point where you see that swelling as the branch meets the trunk. It’s called the collar, and should be left to give the best healing. You will have nice trees with tall trunks. By the way, blue spruce is not a pine tree.

  31. July 18, 2020 by gary kohel

    l live in central wi and have a windbreak with younger white pine 4-6′ tall. Out of approx 200 trees,I had 30 trees where the tip (approx top 12″) had died. There is no sign of bugs or or bird damage.

    1. July 18, 2020 by Dave G

      Hard to say on that one. At least it wasn’t most of the trees. Very likely, especially with such young trees, a new leader will naturally develop. It could conceivably be white pine blister rust. Look for a growth at the base of the dead area next year. Google it for some pictures of what to look for – it’s the spore producing part of the fungus. If you have that you should take another foot off, and let a new leader develop.

  32. July 21, 2020 by Kelli

    I live in northern Utah & have an Evergreen Tree that is yellowing from the inside out very rapidly. I do see some possible holes on the bottom of the trunk. The top looks healthy but I see yellowing all around & the tree does get full sun & water. Can I actually successfully treat a tree if it has borer/beetles? I have photos.

    1. July 22, 2020 by Dave G

      If this is a tree that is valuable to you, it would be best to bring in an arborist. That yellowing could be natural as the tree adopts a more open adult habit, or it could be a problem, but it isn’t possible to say without seeing and examining the tree.

  33. July 26, 2020 by Dorinda Dec

    I live in NJ, and I have a pine tree that suddenly is losing needles. It was fine in the Spring, had new growth, and nothing appeared to be wrong. Now the needles are falling off, before I even have a chance to see they have turned brown. We had a few weeks with out rain, but nothing bad, or out of the ordinary, and for the last few weeks rain has been fine. I dont see any bugs, I don’t think there is any fungus. There are other plants, so I don’t think there is any poison in the ground. I am very upset, and I dont know what to do.

    1. July 27, 2020 by Dave G

      Are these the new needles from the spring shoots, or older ones, further down the stems? If they are older this is normal. ‘Evergreen’ trees don’t have leaves that last forever – just ones that live more than a single season, or sometimes simply don’t drop in the fall but at some other time. With pines, the needles usually live 2 to 4 years, depending on the species. Normally the oldest leaves turn brown and fall in early summer, once the new set have matured. All those pine needles underneath older trees? the result of yearly shedding of the oldest needles. If this tree is fairly new many of the stems won’t have had needles old enough to start falling like this, which is why you didn’t see this in earlier years – now they do and it will be a normal annual pattern. Same for cedar and all other evergreen trees, of all kinds.

      If these are new needles you have a more serious problem and should have a qualified arborist take a look. Hope this helps.

  34. September 1, 2020 by Marjorie P.

    WE have a beautiful white pine, but recently we see a white fuzz on the branches. The fuzz is not at all sticky, but rather is quite dry and can be partially brushed off. We don’t know what this is or what to do. It is spreading to other branches.

    1. September 1, 2020 by Dave G

      It sounds a lot like the Pine Bark Adelgid, but usually that is sticky underneath the powder. This is described in detail in an earlier answer, higher up this thread. I can’t think of an alternative. Easily controlled, and shouldn’t cause long term damage.

  35. September 23, 2020 by Lynee McMillan

    we have ponderosa pines that have orange stripes going up the bark. Some may on the bark and some under the branch. There are some that have what I call squiggly branches. The branch curl up usually starting in one spot then expand to the rest of the tree. There are some trees that get skinny then end up dying. The branches that have orange under the branch seems to be weaker and more likely to break when the wind blows. It seems that the trees with orange tend to eventually die. It seems to be spreading to other nearby trees

    1. September 24, 2020 by Dave G

      Sounds like they are in a bad way! The curly branches suggest your trees have Elytroderma, a common fungal disease that also causes bark death. The orange I suspect is the traces of bark beetles, more likely to infest trees weakened by the fungus. It could be you are in an area where ponderosa pine is not a good choice – either for soil or climate – which would make them more susceptible.