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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 22 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. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

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