Odd Chlorosis on Quercus Rubra....Again

[rfwoodvt]

Hey All!

Getting a number of Quercu Rubra that, from a distance, look to be "dusty" with a tannish haze.

We had this problem several years ago and it seems to be the same general trees suffering again.

Essentially there is a chlorosis on the upper leaf surface, orginating near the veins and progressing outward. Instead of the usual yellows or browns I'd expect from chlorosis or necrosis it is going tan.

There is no evidence of the color change on teh bottom of the leaves and the margins are still deep green.

Symptoms appear generally throughout the tree in question and in a group of trees some may display the symptoms while others do not.

We are having a dryer summer than usual.

Most all chlorosis images I ahve seen though, show the chlorosis starting at the margin and working inward.

Again, this is starting at the vein and moving outward.

BTW, I have yet to see these symptoms evolve into complete chlorosis or necrosis of the leaves, generally it gets to be about 50% and holds there.

Again, it almost from a distance it looks like the tree just came in from the "dusty" trail.

Thoughts?

(PS no new pics but I posted this question a while back...will see if I can find pics from then.)

 

[rfwoodvt]

Old posting with Pics

Here is the old post with pics and thoughts....

http://www.treebuzz.com/forum/showflat.p...=true#Post30250

I'm inclining to think it IS some form of abiotic environmental cause....

Would still love to see if anyone else has pics of such changes...and a fairly sure diagnosis.

 

[mrtree]

Re: Old posting with Pics

I would also be inclined to think that it is an environmental effect. Have seen something similar and not been able to pin-point it. Mine was browner and not spread on every leaf. It is not what I would call chlorosis

I would check some leaves with a microscope and maybe some tests from an extension lab. You might just see something. Drought does not seem likely as Quercus rubra are pretty tough trees.

I wonder about pollution damage. What about ozone damage?

 

[guymayor]

Re: Old posting with Pics

doubt pollution or ozone; most of those symptoms are interveinal, not veinal, chlorosis.

 

[rfwoodvt]

Re: Old posting with Pics

Hey Guy!

Great to see your reply here. Any thots on what would cause the veinal tanning?

Seems odd that it occurs on the upper but not lower surface.

Last time I compared leaves the tanned leaves were indistinguishable from the non-tanned when viewed from the bottom sides.

This Year I have seen some similar tanning occur on Feed-Corn leaves, though only the upper leaves, and the tips. In these cases the browning/tanning seems to begin a the center and rapidly move outward and mainly the upper 25% of the leaf to the tip and not over all the plant, just those most exposed to the sun/wind.

A local Horticulturalist (self proclaimed) suggested that the tree may be down-regulating its photosynthisis by restricting the chlorophyl, or that there may be a "sun-burning" effect going on, especially if the trees are relatively unfamiliar with large amounts of sun. Meaning, edge trees or trees recently exposed to more sun.

Seems plausable but, still nagging doubts.

Would really like to nail this one down.

 

[guymayor]

Re: Old posting with Pics

[ QUOTE ]

This Year I have seen some similar tanning occur on Feed-Corn leaves, though only the upper leaves, and the tips. In these cases the browning/tanning seems to begin a the center and rapidly move outward and mainly the upper 25% of the leaf to the tip and not over all the plant, just those most exposed to the sun/wind.

[/ QUOTE ]Dang boy you are starting to think like a scion twist!

Yer way ahead of me on this one. keep lookin!

 

[mrtree]

Re: Old posting with Pics

I found a red oak today with the same symptoms. Upperside "chloritic" lower side fine. The upper surface seemed glaborous, but this could be rubbed away.

The tree was perhaps 15 years old, in a quite subdivision, and planted next to the road. The most interesting thing was an english oak 50 feet away that was perfectly happy and showed no signs of this abnormal upper surface to the leaves.

 

[Chum]

Re: Old posting with Pics

Changing with the times.

 

[Eric_E]

Re: Old posting with Pics

Lace Bug, probably gone now. Check the underside of the leaves for excrement spots and old cast skins.

 

[SRTFAnatic]

Re: Old posting with Pics

when you're doing a canopy inspection, i would give serious thought to utilising the SRT. Incorporating a valdotain tresse should show those pesky buggers!

 

[rfwoodvt]

Re: Old posting with Pics

Update:

Eric, no indication of causation by insects.

I looked at some of the trees that have exhibited this mid summer tanning each year (it seems to be a recurring issue on these trees).

I found an interesting pattern of coloration as the leaves emerged. I noticed that as they emerged many of the leaves were bright green throughout as expected, but the center of the leaves showed signs of fall color.

It looked almost as if the leaves were turning green from the margins towards the center of the leave.

Now that we have full emergence and size all the leaves are traditional Dark Green throughout.

Interesting note too is that some trees that have not shown the mid summer chlorosis had the emergence brown coloration in the center of the leaves.

Maybe this is normal but it is the first time I had noticed it myself.

Anyhow, the original question about the summer tanning still remains...thots?

Iron?
down regulation of chlorophyl?

Should I offer a reward for the first correct answer?

 

[rageaholic]

Re: Old posting with Pics

I agree with your "self-proclaimed" Horticulturalist. After viewing the pic you posted on your old post, I would venture that the tree is simply regulating its photosynthetic capacity simply because of the environment. I've seen this recently down here in Texas...a few years ago we were in a really big drought (surprise, surprise) and I was seeing this all over the place. I was a treatment tech at the time, so I got to see a lot of sick trees. Anyways, that's my two cents.

 

[Chum]

Re: Old posting with Pics

"I would venture that the tree is simply regulating its photosynthetic capacity simply because of the environment."

This is a growing new event down here - but I'd like to ad that haze is more the trigger than drought. One reactive problem is when a weather event suddenly changes the loads of ozone and other particulate - for a short while - the "sensitive" leaves receive a shock load of UV-band intensity, something science can't fix and another componant of declined immune response to other threats, not to mention the loss of carbohydrate stores needed to beef-up for a winter.