Can you tell me what is causing the branch tips of my Norway spruce to drop?
Last fall a relative showed me a picture of her evergreen tree with dozens of branch tip segments which had fallen to the ground intact and green. I'd heard of something similar happening in the Black Forest of Germany in the 1990s, but to my knowledge the cause was never determined. Now it's happening to my Norway spruce.
The tree is 100 to 120 years old and approximately 100 feet tall. It is an otherwise healthy specimen which had grown in a cluster of similarly aged/sized trees until a freak wind storm blew the two flanking trees down in 2008. A month or so ago I saw some green branch tips had fallen on the ground, but the loss wasn't extensive. Two weeks ago I noticed a neighbor's Norway spruce showed the same tip loss. Last night's wind blew down many more, and now I'm concerned for my tree's health. This is not rodent damage, as the tips are falling freely. All the needles are still green, so there's no browning or die-off before the fall.
Can you tell me what is causing this and what, if anything, I can do to prevent further damage to the tree?
Ingham County Michigan
Your problems are wearing a squirrel suit. Squirrels are notorious for biting the ends off of spruce branches. They will feed on spruce buds on the fallen branch tips. They don't chew through all the tips successfully and damaged ones fall off when the wind blows.
There is nothing you can do because squirrels move from tree to tree with property boundaries being of no consequence.
I appreciate your effort to answer this question, but after posting it I realized it may be beyond the scope of any experts, since the problem has existed in multiple places on the planet for decades and I know of no formal studies undertaken to find a definitive answer. The closest anyone has come to solving the mystery is to point to some sort of pollution or climate change as the culprit.
Please believe me when I say that I have welcomed squirrels into the yard and have closely observed their patterns of behavior, specifically regarding the Norway Spruce they love to nest in. The damage to my tree is not caused by squirrels, but that's the most common assumption regarding this kind of damage.
I apologise for asking a nearly unanswerable question, as it was not my intention to try to stump an expert. Clearly there needs to be more research done on this issue, and a rigorous study would benefit forests all over the globe. The problem seems to be spreading, and I sincerely hope it doesn't endanger the health and diversity of the earth's forests.
You may be interested in this conversation, which I read last year and which perfectly describes the extent of the damage my tree is experiencing:
If you want to believe that this is a cosmic mystery, that's fine. But I have seen red squirrels doing this and I was not hallucinating. Go to: MSUE News at: http://msue.anr.msu.edu and in the search box in the upper right corner, put in: squirrels, spruce. There are multiple articles from others who are not making this up.
I did read this article from the MSU extension:
It seems that red squirrels are responsible for similar damage, however I stand by my original assessment that the damage is not the same and is not caused by squirrels.
Instead of this issue being a "cosmic mystery" it seems to be a problem not yet researched well enough to definitively point toward a set of factors causing the problem. I had hoped you would be as interested as I am at the potential for globally important research. However, even though I tried to be as polite as possible, I am sorry if you inferred offense where none was intended.
The ends will be slightly ragged where they have been separated. Look to see if any of the buds at the terminal ends are removed leaving just some surrounding bud scales. It will look like petals of a daisy with the center gone. Often, there are many buds that are not disturbed.
I have seen several locations where there have been so many tips removed and on the ground, it looks like green carpet. There is no such thing as a one red squirrel; there are always more someplace. They are an aggressive pack of thugs.
Regina, the article from MSU Extension linked in my response above has outstanding photos of red squirrel damage. They illustrate Ms. Voyle's description perfectly. That should help you determine if the damage you're seeing is caused by squirrels or not.
Good luck. I hope you have some answers.