the lawn behind.. looks like what mine does after severe drought ..

where are you .. Pa is kinda big ... ... what is the soil ... any amending at planting ... any history of drought ....

never heard of blight affecting conifers ...

and i dont understand this:

and every year I spray them with mite repellent every few months during mowing season. These are the only ones affected, and it doesn't present itself like the Spider Mite infestation I dealt with a few years ago.

==>> i am not aware of mites attacking ... Thuja... nor spraying multiple times during the years for such.. what are you using ...

all that said.. my WAG would be severely root bound .. pot bound stock ... eventually making watering impossible ...

what if anything did you find.. when you removed the others...

and if you remove this one.. lets get some pix of what is going on underground ...

thuja is just not this disease nor bug prone.. its got to be stock or planting issues ...

ken

Attached is a picture of the affected arb a few minutes ago.

I'm in Berks County, in Southeastern Pa. We aren't in a drought condition. That portion of the hedgerow is at the lowest point of my property which is quite moist even when we've had droughts. The grass on the other side is the neighbor's sand mound, and it has all the dead clumps and sparse growth because they mow *MAYBE* once a month. Lawns don't become lush when they're allowed to grow 18" tall. The soil the arbs are planted in is clay with very little rock.

To clarify my earlier post: I spray all my arborvitae, both Nigra and American, with mite spray three times during the mowing season. The Nigra are the only ones affected since whatever is going on skipped the American arb next to it, and afflicted the next Nigra down wind.

I dealt with a spider mite infestation two years ago. It's a common problem in my area.This is not the same.

If it's a lost cause, I'll cut it down and burn it before winter. However, I have alot of time invested in them and I'm more interested in saving it. I didn't dig up the roots on the last one. I didn't intend to on this one either unless it's absolutely necessary.

the yellowing one is dead ... be done with it ...

the other.. use hand pruners to cut back to a live branchlet ... no reason it should not fill in ..

ken

Do you know what is causing it? I don't want this running down the row killing off all my Nigras.

If it's pestalotiopsis, I treated by wichita blue juniper with something called "Dithane M-45". Over a period of several months, the plant *very slowly* recovered.

Thank you. If it's savable I'm going to give it a shot.

The inside is still a nice shade of green. For some reason whatever gets direct sunlight is turning that color.

If it's pestalotiopsis, I treated by wichita blue juniper with something called "Dithane M-45".

and

Thank you. If it's savable I'm going to give it a shot.

==>>> just dont spend more on a cure... than a new tree would cost.. dont you think ...

you also said: Do you know what is causing it?

==>>> we would have to have all the facts of the quality of the plants.. ball and burlap vs pot .. source [bigboxstore?? ].. how rootbound the pot may have been and what you did about it ...... how they were planted.. when ... how well they were watered the first summer... how much mulch was applied ... what if any weedwhip damage .. what if any lawn spray might be involved ... how you dealt with a pot full of peaty potting media in your bad clay ... which you said was already swampy .... even in drought ...

i have about 150 various thuja ... i have not sprayed one single plant.. in the 13 years i have been here.. i simply dont understand why you are on your second spraying regimen ... IMHO ... bugs attack stressed plants ... and killing the bugs.. does not solve the underlying issue ....

review the attached link.. and look into how it is suggested that in bad clay.. plant be planted high ... never forget.. roots need air as well as moisture ....

i wish you luck ....

ken

Here is a link that might be useful: llink

"we would have to have all the facts of the quality of the plants.. ball and burlap vs pot .. source [bigboxstore?? ].. how rootbound the pot may have been and what you did about it ...... how they were planted.. when ... how well they were watered the first summer... how much mulch was applied ... what if any weedwhip damage .. what if any lawn spray might be involved ... how you dealt with a pot full of peaty potting media in your bad clay ... which you said was already swampy .... even in drought ..."

Bought them in 2007 when they were approximately 16" tall from a nursery going out of business. They were potted. Hole was dug twice as deep and wide as the pot, with compost placed at the very bottom of the hole before putting the unpotted roots in the hole, and backfilled. I haven't mulched them, and we don't use string trimmers on the arbs to avoid trunk damage. The farthest we go is using a walk behind, and pulling any weeds or tall grass.

I never said my lawn was swampy. It doesn't flood, The ground doesn't sink while walking or driving over it. My boots become wetter from morning dew.

I didn't start spraying for spider mites until an infestation in 2011. Before that time, I was under the impression arbs were impervious to almost all wildlife... clearly not so in my region. I don't spray my lawn for weeds. This is the only one with any issues. At the very least the others aren't stressed.