Arborvitae dead leaves - Ask Extension
Hi there! I have three large arborvitae evergreen trees that look like they are dying from the interior, brown “leaves” are dying and I’m worrie...
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Arborvitae dead leaves #888755
Asked October 25, 2024, 2:26 PM EDT
Hi there! I have three large arborvitae evergreen trees that look like they are dying from the interior, brown “leaves” are dying and I’m worried about a mite or insect infestation.
Any info you have would be incredibly helpful.
Pickaway County Ohio
Expert Response
Thank you for contacting Ask Extension.
Arborvitae can have many reasons for the "needles" browning. So I will give you a few causes, but it is important that you do a close examination to help diagnosis your problem.
The browning of the inner foliage could be a normal seasonal drop. The innermost needles gradually turn yellow or brown and will drop to the ground. It is very important to clear out the needles from the inner trunk to give the trunk air flow and eliminate other problems that can later develop due to the moisture retention of the dead needles.
Environmental stresses such as drought ( which we definitely have experienced in Ohio this year) can also cause a larger than normal loss of needles this year.
Spider mites can cause yellowing and speckling of foliage. They feed by penetrating plant tissue. This is less commonly found in healthy trees. They will be visible upon inspection of the branches.
Aphid infestation targets arborvitae and can cause the foliage to brown and kill branches. Careful inspection of the plant can usually find these pests if they are present.
There are many different blights caused by fungi that can cause needles and branches to die. ( needle blight, shoot blight, botrytis blight and cercospora leaf blight just to name a few).
Without photos it is impossible for me to help you identify your trees problems, but I have copied an article that has some pictures that might help you identify the problem. https://ag.umass.edu/landscape/fact-sheets/arborvitae-needle-blight
If you think your trees have a blight it is important to remove all the infected branches. Dead shoots and needles harbor the fungal pathogens and allow them to overwinter in the tree canopy. When they sporulate from the dead tissue the following year, the spores are in very close proximity to newly developing and susceptible tissues. On well-established mature trees, this level of pruning can be a daunting task, but a necessary one if the disease is to be successfully controlled.
You can use a fungicide as a preventative measure in the spring.
Below are a few articles with some information that might help.
You can always clip a branch that is beginning to show a problem and take it to an established nursery for assistance in diagnosis or you local extension office. Also try to get some photos of the trees.
Thank you for contacting Ask Extension.
https://apps.extension.umn.edu/garden/diagnose/plant/evergreen/arborvitae/patchyyellowtobrowndiscoloration.html
https://extension.psu.edu/spruce-spider-mite
https://yardandgarden.extension.iastate.edu/faq/why-inner-growth-my-arborvitae-turning-brown
https://extension.psu.edu/arborvitae-diseases
Arborvitae can have many reasons for the "needles" browning. So I will give you a few causes, but it is important that you do a close examination to help diagnosis your problem.
The browning of the inner foliage could be a normal seasonal drop. The innermost needles gradually turn yellow or brown and will drop to the ground. It is very important to clear out the needles from the inner trunk to give the trunk air flow and eliminate other problems that can later develop due to the moisture retention of the dead needles.
Environmental stresses such as drought ( which we definitely have experienced in Ohio this year) can also cause a larger than normal loss of needles this year.
Spider mites can cause yellowing and speckling of foliage. They feed by penetrating plant tissue. This is less commonly found in healthy trees. They will be visible upon inspection of the branches.
Aphid infestation targets arborvitae and can cause the foliage to brown and kill branches. Careful inspection of the plant can usually find these pests if they are present.
There are many different blights caused by fungi that can cause needles and branches to die. ( needle blight, shoot blight, botrytis blight and cercospora leaf blight just to name a few).
Without photos it is impossible for me to help you identify your trees problems, but I have copied an article that has some pictures that might help you identify the problem. https://ag.umass.edu/landscape/fact-sheets/arborvitae-needle-blight
If you think your trees have a blight it is important to remove all the infected branches. Dead shoots and needles harbor the fungal pathogens and allow them to overwinter in the tree canopy. When they sporulate from the dead tissue the following year, the spores are in very close proximity to newly developing and susceptible tissues. On well-established mature trees, this level of pruning can be a daunting task, but a necessary one if the disease is to be successfully controlled.
You can use a fungicide as a preventative measure in the spring.
Below are a few articles with some information that might help.
You can always clip a branch that is beginning to show a problem and take it to an established nursery for assistance in diagnosis or you local extension office. Also try to get some photos of the trees.
Thank you for contacting Ask Extension.
https://apps.extension.umn.edu/garden/diagnose/plant/evergreen/arborvitae/patchyyellowtobrowndiscoloration.html
https://extension.psu.edu/spruce-spider-mite
https://yardandgarden.extension.iastate.edu/faq/why-inner-growth-my-arborvitae-turning-brown
https://extension.psu.edu/arborvitae-diseases
