Blue Spruce Needle Cast

Asked August 28, 2018, 2:49 PM EDT

Our blue spruce has needle cast, but it is way too tall to spray. Is there a systemic that can be drawn up through the roots of the plant to protect the spruce from fungal infection?

Lane County Oregon urban forestry needle cast

5 Responses

Before we can best recommend management options, let's confirm that the tree has needle cast. Needle cast in spruce is a fungal infection caused by Rhizosphaera sp. This disease has some distinct symptoms but can also be confused with drought stress.

How was your tree diagnosed? Could you please send some photos as a reply to this email? It would be best to have a photo of the entire tree, one of an individual affected branch, and if possible of the brown dead needles.

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Hi Brooke:

Here are three pictures, one of the north side of the tree, one of the inside of the tree, and one of the middle of the tree. As you can see, there are almost no needles inside the tree, only on the tips. You can now see the sky through the tree where before it was dense with needles.

Thanks for your help!

Carol

Hi Carol,
Thanks for the photos and your patience with the delay. That is a beautiful tree that adds a lot to your landscape!

I don't see the typical signs and symptoms of fungal needle cast from the pictures. (needle cast typically strikes the younger growth first). Looks like the older needles are dropping. Some of that is normal as the sunlight isn't reaching the inner parts of the branches so the tree sheds the unneeded needles but there might also be excessive shedding due to drought/heat-stress response. (We've had some pretty hot, dry summers of late and many of our conifers in the landscape are struggling with stress.).

If you prefer someone look at this sample in person, you can drop off an affected branch at the OSU Extension Lane County office. That office has a plant clinic run by Master Gardener volunteers that can take a fine look at the sample. Contact information can be found here: https://extension.oregonstate.edu/lane
Until you get a positive diagnosis of needle cast (or another disease issue), I wouldn't recommend any pesticide treatments at this time.

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Thanks for the info! We do have some dead spots in the front of the tree and almost no needles left on the inside of the tree, which we have never had before. Plus, we've never been able to see through to the other side before, but you think that could be due to drought? There is a lawn to the right of it that we water, so part of the tree is getting water twice a week. Oddly, the branches on the front of the tree are droopy where it actually gets water, whereas the backside, that gets no water is not droopy and the roots are at the surface. I can actually pull them up easily, they are so lacking auxiliary roots. Would deep watering help that part of the tree that is not getting water? And is there something I can feed it to help it resist the stress? Thanks for your feedback!

Carol

It's always so tricky to know what exactly is causing the issue with large trees! Many of our large conifers are showing accumulated stress from years of drought and hot weather. Applying deep irrigation evenly around the tree during the dry summer months is good. You could try adding a layer of soil or additional mulch to cover the exposed roots. Larger trees generally don't need fertilization (and it's difficult to apply). It looks like your lawn is well maintained so the roots are likely able to pick up some nutrients from there.

Here are some more tips from one of our recent news releases on drought stress in conifers: https://today.oregonstate.edu/news/conifers-–-especially-doug-firs-–-are-suffering-drought

Just out of curiosity, are you in the area of Lane County that was affected by the ice storm last year?