What is wrong with this arborvitae - Ask Extension
This tree was here when I purchased the home 2 years ago, I don't know much about it. It looked healthy up until recently; now there are bare/brown se...
Knowledgebase
What is wrong with this arborvitae #863378
Asked April 04, 2024, 5:47 PM EDT
This tree was here when I purchased the home 2 years ago, I don't know much about it. It looked healthy up until recently; now there are bare/brown sections and this white stuff on the branches. I don't know if this is from fungus or an insect, please help. Thank you
Mercer County West Virginia
Expert Response
I don't think this photo attached to my first post
Thank you for the excellent pictures. Looking at the location of the injury, I am lead to believe that side of
the tree received some ongoing winter injury (from either wind or salt), there may have also been stress if the sidewalk has been replaced or repaired in the past 5-10 years.
I believe the main problem with your spruce to be Cytospora canker which is caused by the fungal pathogen Cytospora kunzei (also known as Leucostoma kunzei). This is an opportunistic pest and will attack stressed trees. This pathogen has been working below the surface of the bark for a while. It won't show symptoms until it is well established. It is also hard to treat canker forming diseases in trees as most of the fungal activity occurs in places we can't reach. It spreads by spores that are released on the bark and splashed around by wind and rain. Existing damage such as winter burn, insect feeding sites, or pruning wounds provide openings for this new spores to get established.
The tree also has another fungal pathogen as shown by the black spore releasing sites on the needles. I need would need a lab test to positively identify this fungus.
Unfortunately you will need to prune out the affected limbs well back beyond the parts that are symptomatic to keep the disease from spreading. This will severely disfigure your tree as conifers do not sprout new branches back the way deciduous trees do and those spaces will be forever bare. This honestly may be a blessing in disguise as this tree has nearly outgrown it's growing area and will likely begin to cause damage to your foundation or the sidewalk if it gets much bigger.
However, if you want to try to save the tree.
Step one is to remove all the fallen needles and branches and burn or bag them for disposal. To help control the pathogen affecting the needles you can apply a copper-based fungicide or mancozeb. This will need to be applied when the new growth is half expanded and again 3-4 weeks later. Good coverage is essential and this is a very dense tree. Take your time and get the spray in deep.
Do not disturb the soil in the rest of the planting bed. Apply a 2 inch layer of mulch to protect the roots from drought stress. If we have a drought this summer you will want to slow water the tree with an extended drip or trickle of water. (A 5gal bucket with small holes in the bottom works well for this).
After the spring rains die down, prune out the cankers. The proper way to prune conifers is: if you cannot leave some green, you must prune all the way back to the trunk. Do not cut flush against the trunk but try to identify the small flare at the base of the branch and leave that part on the tree. Do not prune when it is wet or predicted to rain soon. Because this tree is already infected, you will need to sanitize your cutting tools between each cut to avoid spreading the spores into the new wound (wipe it off with a clean paper towel and isopropyl alcohol). If you notice discoloration around the outer ring of any cut that goes to the trunk, the fungus is already deeper in the tree and will continue to spread.
Finally, while this is not advisable in most pruning situations, because there is such a great fungal load you are removing, I recommend you use wound paint to cover the openings until the tree can naturally seal them.
the tree received some ongoing winter injury (from either wind or salt), there may have also been stress if the sidewalk has been replaced or repaired in the past 5-10 years.
I believe the main problem with your spruce to be Cytospora canker which is caused by the fungal pathogen Cytospora kunzei (also known as Leucostoma kunzei). This is an opportunistic pest and will attack stressed trees. This pathogen has been working below the surface of the bark for a while. It won't show symptoms until it is well established. It is also hard to treat canker forming diseases in trees as most of the fungal activity occurs in places we can't reach. It spreads by spores that are released on the bark and splashed around by wind and rain. Existing damage such as winter burn, insect feeding sites, or pruning wounds provide openings for this new spores to get established.
The tree also has another fungal pathogen as shown by the black spore releasing sites on the needles. I need would need a lab test to positively identify this fungus.
Unfortunately you will need to prune out the affected limbs well back beyond the parts that are symptomatic to keep the disease from spreading. This will severely disfigure your tree as conifers do not sprout new branches back the way deciduous trees do and those spaces will be forever bare. This honestly may be a blessing in disguise as this tree has nearly outgrown it's growing area and will likely begin to cause damage to your foundation or the sidewalk if it gets much bigger.
However, if you want to try to save the tree.
Step one is to remove all the fallen needles and branches and burn or bag them for disposal. To help control the pathogen affecting the needles you can apply a copper-based fungicide or mancozeb. This will need to be applied when the new growth is half expanded and again 3-4 weeks later. Good coverage is essential and this is a very dense tree. Take your time and get the spray in deep.
Do not disturb the soil in the rest of the planting bed. Apply a 2 inch layer of mulch to protect the roots from drought stress. If we have a drought this summer you will want to slow water the tree with an extended drip or trickle of water. (A 5gal bucket with small holes in the bottom works well for this).
After the spring rains die down, prune out the cankers. The proper way to prune conifers is: if you cannot leave some green, you must prune all the way back to the trunk. Do not cut flush against the trunk but try to identify the small flare at the base of the branch and leave that part on the tree. Do not prune when it is wet or predicted to rain soon. Because this tree is already infected, you will need to sanitize your cutting tools between each cut to avoid spreading the spores into the new wound (wipe it off with a clean paper towel and isopropyl alcohol). If you notice discoloration around the outer ring of any cut that goes to the trunk, the fungus is already deeper in the tree and will continue to spread.
Finally, while this is not advisable in most pruning situations, because there is such a great fungal load you are removing, I recommend you use wound paint to cover the openings until the tree can naturally seal them.
