What's killing my Thuja "Green Giants"?

[Woodwork]

This is very strange. We have some of the best soil around here that I've ever seen in my life...so-called "fine sassafras sandy loam," basically lots of organic material mixed into an alluvial deposit left in a gigantic river delta (Susquehanna) when the glaciers receded and the Chesapeake Bay filled. Pretty much everything grows in this soil like a house afire, but my Thuja "Green Giants" (T. plicata x T. standishii) are dying all over.

It starts like this:








And then it proceeds (within a year) to this:



What's REALLY weird is that as best as I can remember, this dead Thuja started out having a brown dead spot on the other side of the tree, where the tree is now green (circled area):



In other words, the circled green area was the first area that turned brown on the tree, then the whole tree died, but then where it first turned brown, it turned back to green again!

Does anyone think that last tree has any chance of coming back? I may just leave it for the time being as a natural trellis for hops to grow on...just want a visual screen in winter, mainly.

Does anyone have any idea what's happening here? This is in coastal Virginia, I think zone 8b. Soil gets occasional standing (fresh) water, but never for more than a day, and I don't think EVER where these trees happen to be planted...water table is generally 2 to 6' below grade.

I had always heard that Thuja GG was pretty much immune to any diseases or pests, but these don't seem to be doing so hot...hell, the miserable leylands are outliving them.

TIA for any help.

Jeff

 

[Jemco]

Overspray drift from the cornfields?

Jemco

 

[Woodwork]

Overspray drift from the cornfields?

That's what I thought, too, at first, but that theory doesn't make sense when you consider where the brown spots are appearing (as often as not, on the side that's opposite, rather than adjacent, to the fields) ... or when (in mid- to late-summer, long after the farmers are done with weed killer, at least for corn). I'm thinking maybe some kind of fungus?

I grew these trees from 6" liners ... so they're well-established before they start failing.

I believe the farmers here use atrazine herbicide for corn...anyone know Thuja's tolerance for atrazine?

 

[Jemco]

Simplest way to definitively determine what's goin on?

Take a half dead branch to your nearest plant pathology lab for diagnosis.

Most counties have plant pathology labs, and many AG universities as well.

Well worth the fee IMO.

Jemco

 

[Jemco]

My money's on Atrazine poisoning, being confirmed by a pathology report.

If so, get a second independent report from another reputable pathology lab before taking any action.

Apparently mature trees can withstand a few small doses and recover, but repeated applications will most definitely kill any tree.

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Jemco

 

[Woodwork]

Thanks, Jemco. I'll do that, though I suspect the local outfit guys are tied in with the local farmer good ol boy network pretty well. Maybe I'll send a branch to Virginia Tech or something like that.

I appreciate your help. Never would have thought of that.

Yeah, I saw that same document about herbicide damage, sounds like atrazine is pretty strong stuff.

 

[evo]

Any small black dots on the underside of the leaves? Likely need a magnifying glass