[Tweeters] OT - Douglas-fir die-off

Denis DeSilvis avnacrs4birds at outlook.com
Thu May 30 09:04:11 PDT 2013


Tweeters,

(Off topic)

Thanks to those of you who answered my request regarding the conifer -
mostly Douglas-fir - die-off that I've seen in many hundreds (and affecting
quite possibly thousands) of trees in south Pierce and north Thurston
counties. I've received information indicating that it's more widespread,
i.e., around Covington, Tenino, US 12W, and northward as far as Southcenter,
and eastward along Hwy 702. I've also received notes indicating
possibilities that include spruce budworm, Swiss Needle Cast (fungus),
winter burn, and laminated root rot. Until someone from an institution like
WSU or DNR takes a good look at a few samples, one other possibility, which
I received a note on from a colleague, exists: drought stress. Here's an
edited note concerning this:



"I checked with WSU Plant Clinic and they said they thought the die back is
due to the weather that was unseasonably warm and dry early which lead to
drought stress on younger trees. The key was the way they die off, i.e.,
typically [the] top dies back due to negative hydrostatic pressure higher in
the tree. They do not agree that it is winter die back [winter burn] since
this winter was very mild. The last winter die back we had was 2009 and due
to winter desiccation. I note that this is true from observation with the
lower branches staying green and healthy. Also individual branch die back
from the same phenomenon on some trees (i.e., the entire branch is affected
where pathogenic disease would be spotty symptoms). The lack of recovery is
due to the same thing and may be resolved by all this rain we are having in
terms of some recovery. Apparently when the tree shuts down that is fairly
permanent due to the negative hydrostatic pressure in upper canopy so those
younger trees are probably gone for good. . They were very clear that they
do not think it is pathogenic caused but are willing to look at a specimen
to confirm that if I can find a small one. I will take a sample in to the
Plant Clinic in the next week or two to confirm all this."



If most of the affected trees recover after the incredibly wet week+ we've
had in this area, it would lend credence to the drought-stress hypothesis,
without even taking samples. If it continues to affect more trees, likely
not. Along the street and behind homes where I live in Roy, I'd estimate
over 50 Douglas-fir and noble fir trees have been affected, including many
(20 or so) that have died. I'm monitoring the three trees on our property
that appear to be affected, as well as several more nearby. I've noted that
several larger trees have died completely, but it may be that drought-stress
was a tipping-point factor in their demise.



Please let me know if you believe you're seeing trees continuing to be
affected.



Thanks for all your support, and may all your birds be identified,

Denis DeSilvis

Roy, WA

Mailto: avnacrs4birds at outlook.com



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