Hi Lois,
Sorry to hear about your Weeping Norwegian Spruce. Great to hear it is well established. Since the Norwegian Spruce can be one of the trickier specimens to grow in our climate. They are unfortunately not well adapted to hot and dry locations and can be one of the most problematic of the spruces of the west. (https://extension.illinois.edu/sites/default/files/plant-clinic-report-spruce.pdf). Often, trees can sometimes exhibit symptoms that has been the result of stress from seasons past (i.e. we had a harsh winter a few years back and a spring like we've never seen this past season). If you could provide a few more pieces of information we can hopefully drill this down to a specific issue:

1. What is the sun exposure of this tree? direction? full sun, partial sun, part shade, full shade, etc.
2. Is it planted in proximity to any other plants or a structure/building?
   
3. What are you watering habits with this tree? Does it get watered during the winter?
4. Are you seeing any symptoms on the yellowing/falling leaves aside from discoloration? Are you seeing needles die and drop off? Branches as well? Do the symptoms seem to show up on the inner portion of the canopy first and work their way out? i.e. from older needles to younger? Bottom up or top down, etc.
5. Are you seeing any girdling roots? here's a photo: https://www.missouribotanicalgarden.org/Portals/0/Gardening/Gardening%20Help/images/Pests/Girdling_Roots1424.jpg
6. Do you have some leaf/needle/branch samples you can send photos of or bring to the office in person?

Depending on the symptoms we're looking at based on those questions, it could be a number of different issues:
1. NEEDLE-CAST/FUNGAL
In the case of a fungal issue (likely Rhizosphaera spp. or Stigmina spp.), the most obvious symptom will be browning needles, needle drop, and branch dieback. These species prefer cool temps and prolonged spring humidity (which we did have this spring). Symptoms are often not noticeable in the first year of infection. The disease can survive on the infected needles in the winter. Disease management includes reducing abiotic stresses by using proper irrigation, fertilization and mulching, pruning dead and dying branches or removal of dead trees, avoiding irrigation with sprinkler (use a watering spike), active scouting of disease problems, and winter watering. If you suspect something fungal, application of broad-spectrum fungicides such as copper, sulfur, chlorothalonil, or mancozeb by closely following the label and instructions. As a last resort, replacing the tree with one more well adapted to our zone is a drastic option if the tree is too far gone. (https://ipm.missouri.edu/MEG/2022/3/spruceDiseases-PT/#:~:text=The%20most%20important%20disease%20of,needle%20dropping%20and%20branch%20dieback.)
1. SNEED: Sudden Needle Drop of SpruceLeaves will drop seemingly randomly. This is associated with a fungus called steomelanomma holmii. Trees that are already suffering as a result of insufficient care will be especially susceptible. Reduction of environmental stress is the best means to address this issue.
2. CANKERIf you're seeing any patches of white-blue resin being excreted by the tree, on branches or dripping on the ground, it may be infected with Cytospora Canker. Though this is less likely. If this is the case, there is unfortunately no fungicide available to treat it. It will again come down to cultural practices and care.

3. PHOMOPSIS TIP BLIGHTThis is even less likely than the last issue but a possibility as it is generally found on juniper, though it has been increasingly appearing on spruce. Symptoms include needle drop, tip blight, and girdling of branches. Here is a pretty clear photos of how this ailment exhibits: https://ipm.missouri.edu/MEG/2022/3/spruceDiseases-PT/figure3.jpg

4. SCALESPine needle scale (Chionaspis pinifoliae) goes through a complex life cycle and can produce multiple generations in a season. So they can be tricky to combat. Because scales are protected by armor, any preventative insecticides such as neem and horticultural oils are ineffective unless used at the right time. Generally early spring during the crawler portion of their life cycle, immediately after egg hatch. Biological controls might be your best bet here. I am attaching a pdf with some photos of pine needle scale to assist you in identifying your issue, here: https://extension.missouri.edu/media/wysiwyg/Extensiondata/Pro/PlantDiagnosticClinic/Docs/pine-needle-scale-highlight.pdf
5. SPIDER MITESYou'll see these as small yellow specks on the needle. As they progress and become an infestation you'll begin to see tenting and webbing on branches and leaves. They can also live in nearby weeds, so be sure to keep your tree site tidy. Your best options for this issues is a miticide (not a broad spectrum insecticide) or biological controls (lacewings or ladybugs)

Here are a few useful resources that may help you determine what's happening with your tree:

• University of Misourri - Integrated Pest Management: https://ipm.missouri.edu/MEG/2022/3/spruceDiseases-PT/.
• USDA - Pine Needle Scale: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5351723.pdf
  
• https://extension.illinois.edu/sites/default/files/plant-clinic-report-spruce.pdf

Best,

CSU Extension Boulder County Master Gardeners

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• Boulder County Parks Master Gardeners

Mon 10/16/2023 9:14 AM

Hi Boulder County,

Question #0122958 has been assigned to you by CSU E.

30 yr old Weeping Spruce Yellow Needles

Our revered 30 yr old Weeping Norwegian Spruce started showing yellow needles at first (2 weeks ago) I thought it was just a dead lower branch but this morning it seems to be in a lot of spots. Kind of a bright yellow. On line it looks like it may be Needle Cast Disease that needs to be treated with a fungicide. Any help appreciated. Seems like we need to act fast. This tree is our favorite....

Thank you

From: Lois LaCroix
Submitted: 10/13/2023 12:21 PM

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