Subject:    HORT ALERT:  Dying Spruce

November 15, 2007

 

I have been receiving calls and e-mails from all over the tri-state area about spruce trees and other conifers (including pine, arbor vitae, and juniper) that are dying quickly and suddenly.

 The common symptom seems to be the “sudden” death of numerous branches, or even the entire tree.  Often times, the needles completely drop off the branch without turning brown first (although some reports do indicate yellowing and browning of the needles first).  In many cases, the needles deep within the body of the plant drop first, and the ends of the branches lose their needles last.

 Many of the spruce are well-established, and have been in the location for 5 to 50 years.  Only a few of them were planted recently enough for me to think that transplant shock could be a factor.

I have not been able to find a single consistent factor that could cause this widespread decline.  Some of the trees had evidence of girdling roots, but not all of them.  I found no evidence of Cytospora Canker, a devastating disease of spruce.  Certainly, the drought of 2007 was an added stress that may have “tipped the needle” and sent the trees into decline, but it wasn’t severe enough to kill all the spruce.

 I contacted the Purdue Plant & Pest Diagnostic Lab, and they sent me back the following information:

 "From: Gail Ruhl, Purdue P&PDL:

I suspect the symptoms are related to root stress.  We have received a number of samples and phone calls within the last several months.

 The symptoms on established conifers are similar to those that can be observed on a cut Christmas tree. Even after the tree is placed outside following the holiday season the foliage remains green, sometimes for more than 5 months without a single functioning root. Only when warm temperatures arrive in late spring will the foliage on this cut tree start to lose moisture and turn brown.  Once this process begins, the discoloration will continue to develop until the tree is completely brown and the foliage falls off the branches.  But until a significant portion of the crown turns brown, the casual observer may not notice the subtle change in needle color.  

The same thing happens in landscape conifers when roots or cambial tissue are damaged.  The structure of the needles, and the waxes that coat the foliage, help to inhibit moisture loss and the foliage remains green.  If the root damage occurs when temperatures are cool, then the foliage can appear healthy for several weeks or months after the roots have died.  By the time the foliage begins to turn brown the roots may have been dead for weeks or months.  Conifers often respond all at once when they reach some 'critical threshold' of stress. Frequently this is exacerbated by disturbances in the root area, drought or other environmental, site or cultural problems. Injury to cambial tissue (tissue that transports food and water) on thin-barked trees may also have occurred this past spring when unseasonably high temperatures in March were followed in April by a sudden drop in temperature. Delayed symptom expression consisting of branch dieback and even tree death is likely a result, in part, to the tissue damage that occurred following this extreme temperature fluctuation.

 One clue to determining if a browning evergreen will produce new growth is to check the buds at the tips of the branches - if they are green inside, then new growth may develop in the spring.  If the buds on the ends of all branches are brown and dry, the tree will not recover. "

  

Another item that came out in our conversation was that “wet feet” (poorly drained, waterlogged soils) are especially damaging to spruce, pines, and many other conifers.  We (southwestern Indiana) have experienced several prolonged wet periods over the last few years, especially in the spring.  This could have started the domino effect that led up to our current rash of spruce die-offs.  Indeed, I have recognized wet feet as the main culprit behind the chronic problems we have with white pines. 

Wet feet will also encourage root rot disease.  Two of the most common root rot diseases are Pythium and Phytophthora Root Rots.  These are caused by soil-borne fungi.  In dry, well-drained areas, the diseases have little or no effect; but in poorly drained soils, they easily infect the roots of susceptible species.  There is no chemical cure or preventative for this.

 Right now, there is not much we can do.  As Gail Ruhl said, if the entire branch is dead and there’s no green buds on the branches, then those limbs are dead, and should be removed.  If the entire tree is brown, remove it quickly, before bark beetles and borers that may have been attracted to the dying tree escape and infest nearby trees.

 If there is still life within your plant, I strongly suggest that the best option is to irrigate.  Apply 1 inch of water per week, starting now and continuing until the ground freezes.  PLEASE NOTE:  Many of the people who claimed to have watered their trees during the drought DID NOT, in fact, water their trees properly.  Remember, the roots of all trees extend way beyond the ends of the branches...at least as far from the tree as its height.  For most trees 10 feet tall or more, you need to water a goodly part of your yard.  Watering ONLY under the branches only provides water to maybe a quarter of the root system; if the non-watered roots die, your tree will die, too.

 I will continue to scour the Midwest Universities for more clues as to what is going on, but for right now, I think we need to chalk this one up to hostile environmental conditions.