Lichen Problems on Flowering Trees

Discussion in 'Garden Pest Management and Identification' started by mitten, Nov 10, 2007.

  1. mitten

    mitten Member

    Messages:
    2
    Likes Received:
    0
    Location:
    Florence, Oregon, USA
    In checking the internet, it appears that there is nothing I can do to get ride of grey fern like lichens on two flowering cherry trees. I have tried fungicides sprayed and have hand picked off lichens in the past. The lichens now cover most of the branches and trunks of my two trees and do not look good. Is there anything I can do to rid my trees of this problem?
     
  2. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

    Messages:
    11,411
    Likes Received:
    500
    Location:
    Britain zone 8/9
    It isn't a problem, they don't harm the tree at all. Just leave them alone and enjoy the fact that you have air clean enough for them to grow well!
     
  3. Ron B

    Ron B Paragon of Plants 10 Years

    Messages:
    21,234
    Likes Received:
    781
    Location:
    WA USA (Z8)
    Changing your perspective has the advantage of requiring less elbow grease.
     
  4. charlieinneedham

    charlieinneedham Member

    Messages:
    3
    Likes Received:
    0
    Location:
    Needham, MA USA
    Have the "experts" ever considered they are barking up the wrong tree with regard to lichens? While they may be "harmless" to mature large trees with thick bark, how about young ornamental trees with thin bark? Couldn't the prolonged moisture contact under the lichens harm the bark? I believe I observe this on my Kwanzan cherries, Korean dogwoods, Thundercloud plums and crabapples. The [over]use of my sprinkler system undoubtadly contributed to the problem in my yard, and modification of watering seems to have helped. (I realize rain and mist are the likely culprits in the Pacific Northwest.) But gentle scraping and the spray application of chlorthalonil also have been needed. (I started with the chlorthalonil because I had ot to treat my roses; copper-sulfate seems to be recommended.) The following are threads I turned up on a Google search that may be useful: http://www.gardenopus.com/Lichen.htm, http://www.newton.dep.anl.gov/askasci/bot00/bot00259.htm.
     
  5. mitten

    mitten Member

    Messages:
    2
    Likes Received:
    0
    Location:
    Florence, Oregon, USA
    Thank you for your information on lichen problems in flowering trees. In the past, I have tried to pick off the lichens but there are too many of them this year - all over both my flowering cherry trees. I applied a solution of copper-sufide, spraying it on but was only able to use it once since we have had so much rain and cold weather up here in the Northwest this year. Will try and find your recommendation of chlorthaloni at a local nursery. Also have been advised that you need to apply solutions three or four times for them to work. Next time I will try and paint the solution onto the lichen so I won't have to spray it on which usually blows around and is not safe for me to use in that manner.
     
  6. lily

    lily Active Member 10 Years

    Messages:
    366
    Likes Received:
    0
    Location:
    Abbotsford, British Columbia
    What is the difference between lichens and moss? If I have moss growing on my apple tree does that mean there are lichens there too? What do lichens look like? Thanks.
     
  7. Eric La Fountaine

    Eric La Fountaine Contributor Forums Moderator 10 Years

    Messages:
    3,511
    Likes Received:
    235
    Location:
    sw USA
    Around here both moss and lichens are commonly found on trees (and everything else), so you may very well have both. Moss are green plants, lichens are a symbiotic relationship between a fungus and a photosynthetic oraganism, usually algae or cyanobacteria. I am no expert on this, so as to what they look like there are a too many to describe. Mosses are soft and generally green, lichens come in many colours and forms, some are crusty.

    The comment I want to make though, is that I personally find the mosses and lichens that inhabit the trees add so much character and beauty to the trees. The grand old trees with patches of colour and texture defining their trunks are gorgeous. Sometimes on young trees and shrubs it can look odd though, I guess.

    I don't know how much damage either could do to the host plant. They may take a few nutrients from the bark, but that should be no problem. They both get their energy from photosynthesis. Could possibly hold moisture or provide an entry point that could increase the chances of a pathological infection. I have never heard of them causing problems for trees.

    Any arborists care to comment?
     
  8. lily

    lily Active Member 10 Years

    Messages:
    366
    Likes Received:
    0
    Location:
    Abbotsford, British Columbia
    Hi Eric, thanks for your post. My hubby, like you really likes the look of moss on trees. He also agrees that it adds some character. I'm not even going to attempt removing it. I don't particulary like the look of moss but maybe after time it'll 'grow on me' ~ did I really say that? LOL
    I have the moss on both my apple and lilac trees but I pruned them both so maybe some sunshine and air circulation will help keep it under control now. I recently moved here and noticed that the trees and shrubs haven't been maintained in a very long time. I'm looking forward to seeing what else grows around here in the spring.
    Thanks again for your help.
    ~ Lily
     
  9. growing4it

    growing4it Active Member 10 Years

    Messages:
    322
    Likes Received:
    0
    Location:
    vancouver to langley, bc
    I would expect that efforts to remove lichen would cause more damage than leaving the lichen alone. My Ortho's Home Gardener's Problem Solver (ORTHO - the company that makes and sells pesticides!) states that lichen does not harm plants.

    Lichen aren't exactly a fungus and Ortho's doesn't even recommend a fungicide, it recommends pruning to increae light and air flow to discourage lichen, algae and mosses. interesting eh?
     
    Last edited: Feb 9, 2008
  10. charlieinneedham

    charlieinneedham Member

    Messages:
    3
    Likes Received:
    0
    Location:
    Needham, MA USA
    This is an "apples" and "oranges" discussion.
    "Apples" are different than "oranges".
    "Large mature trees with thick bark" are different from "delicate, slow growing ornamental trees with thin bark".
    Because lichens do not harm "large mature trees with thick bark" does not mean they can not harm "delicate, slow growing ornamental trees with thin bark".

    Harmful effects of lichens are well recognized by botantists:
    "Many substances synthesized by lichen thalli have damaging effects on trees…Moreover they sometimes show an extensive penetration of rhyzines through the cork, cortex and cambrium, reaching the living wood (Ascaso et al. 1980)." - http://www.sekj.org/PDF/anbf35/anbf35-071p.pdf
    "Epiphytic lichens can have harmful effects on trees on which they grow. Their hyphae readily tear off areas of both phloem and xylem and they disperse towards the vessels. Thallus penetration produces clear symptoms of chlorosis and ageing of leaves through metabolic inhibitors that, after translocation in the xylem sap, reach leaves and cause abscission. Lichen phenolics block the electron transport between QA and QB sites in the PQ region of thylakoid membranes by inducing conformational changes in a platoquinone-bound protein. Alternatively, they also produce the loss of chloroplastic manganese through a chelation process. For leaves in which lichen phenolics does not easily penetrate through the chloroplast membrane, these lichen metabolites conjugate to indole-3-acetic acid and the subsequent decrease of the amount of free auxin retards or impedes bud evocation and leaf development." - http://www.cababstractsplus.org/google/abstract.asp?AcNo=20053084569


    Harmful thick lichen growth on ornamental trees is an under recognized problem, I believe.
    Like many gardeners, I have been stubborn in trying to grow plants not native to their environment in order to achieve a certain effect. Around the circular driveway in front of my house, I planted multiple Kwanzan and weeping cherries, Thundercloud plums, Korean dogwoods, and crabapples. All acquired varying coats of lichens over not only their trunks, but right out onto the very tips of every branch. I lost many of these trees, but was reassured by my landscaper, nurseryman, and web searches that lichens are "harmless".
    What I observed was that prior to losing a tree, often some of the bark of the trunk or a branch would become denuded. Fingertip pressure of the soggy succulent lichen growth on dead or dying branches resulted in removal of bark. On healthier parts of the tree, the lichen could be easily removed with gentle scraping, but the bark under the lichen growth appeared moist.
    Now I am sure the lichen was at least a bellwether that I had to decrease my almost daily sprinkler system use during summer in a misguided effort to keep my lawn and garden green.
    But even greatly reducing the sprinkler system use did not prevent lichen regrowth in soggy spring, fall, and winter weather, after an initial gently scraping off of the lichen growth. I found that I had to gently scrape the most heavily infested lichen growth periodically and began to spray chlorthalonil after the scraping to reduce regrowth (It appears the most commonly recommended agent is copper sulfate).
    With this regimen, for the last two years my trees seem to have thrived. I have been rewarded with a fireworks display of flowering trees in the spring, and various shades and shapes of foliage all summer long!
    Does this prove the lichen itself was "harmful" to the trees?
    Of course not. But the lichen growth was the "canary in the birdcage" that alerted me to change the watering. And I do believe that the constant moist micro-environment under the lichens on the bark surface of these relatively delicate, slow growing trees led to their decline and demise. I don't know whether it was the moisture alone that affected the bark, whether the moisture augmented growth of a more virulent fungus, or whether lichens release metabolic products that can harm bark, or do so through their rhizines. (The late Dr. Shigo in an article that playfully states, "There are no data that shows lichens cause tree or rock diseases." nontheless goes on to say, "The root-like organs of lichens are called rhizines. The rhizines penetrate rocks and aid decomposition. Lichens also produce acids and other chemicals that break down rocks and other materials.". And in the same article:" "Most cyanobacteria fix nitrogen, which means they have an enzyme system that converts atmospheric nitrogen to ammonia and ammonium ions." http://www.treedictionary.com/DICT2003/shigo/LICHENS.html)
    Visiting various local area nurseries (even Home Depot!) I am struck by the dramatic increase in ornamental trees being sold that are not really native to this area. And the use of automatic sprinkler systems in my area has seemingly become a "necessity". Thus, I am sure my problem with lichen overgrowth must be becoming more common. Nonetheless, it still seems the most common opinion with regard to lichens is to ignore it because "lichens do not harm trees".

    Meanwhile, on a winter walk through a mature Forest, I will continue to admire the abstract art forms of colorful lichens on trees and rocks as an example of nature's magic.
     
  11. lily

    lily Active Member 10 Years

    Messages:
    366
    Likes Received:
    0
    Location:
    Abbotsford, British Columbia
    charlie, thank you very much for this post. What an interesting read. I clicked on the links and was surprised to read that lichens actually have a purpose. Perfume, antibiotics? Pretty amazing to learn all this. Thanks again.
     
  12. Daniel Mosquin

    Daniel Mosquin Paragon of Plants UBC Botanical Garden Forums Administrator Forums Moderator 10 Years

    Messages:
    10,562
    Likes Received:
    608
    Location:
    Vancouver, British Columbia, Canada
    I feel obliged to point out that most of the scientific references above point to leaf tissue damage by lichens, not bark.

    I'd like to see the 1980 et al. Ascaso paper, as that particular one does sound like it offers evidence against convention.

    Re: lichens actually having a purpose - I'll just nudge you into the direction of restating that as "Lichens actually having an economic or utilitarian value for humans". They've been around for around 2000x longer than humans.
     
  13. jimweed

    jimweed Active Member 10 Years

    Messages:
    365
    Likes Received:
    1
    Location:
    Aldergrove
    I am surprised no one has mentioned that Lime Sulphur sets back Lichen's and Moss. Annual treatments of Lime Sulphur keep these to low minimum on your trees.
     
  14. Liz

    Liz Well-Known Member 10 Years

    Messages:
    1,526
    Likes Received:
    2
    Location:
    Victoria Australia [cool temperate]
    How about opening up the area to more light. Down here lichen etc grows on the south side of trees (north up your end). There is less light /sun from the south /north. It is a useful way of telling direction when lost in the bush. If they were mine I too would leave it. I have a prunus with a lovely growth on it. It's on the south side of the house.

    Liz
     

Share This Page