Here is a photo of a couple of the trees for id purposes:

where is the damage in relation to that dog... or the prior owners dog???

or lawn spray???

i cant see the damage on the second pic ...

just snip out the black .. put it in a plastic grocery bag ... and put it in the garbage ...

leave the brown until spring.. if its still there.. snip it off ... then

your plants look fat and happy.. i dont see anything i would worry about.. nor do i see anything worth chems ...

HA!!!! ... lol

ken

The black foliage results from cat or dog urine. I see it all the time and I'm 100% sure that's what it is. You won't find it on a part of the plant that is inaccessible to your dog.

Thank you for the ideas! The damage is a little higher than my corgi or the previous owner's dachshunds could reach. It's possible that a neighborhood dog did it, but the area is a little inaccessible (it's not visible in the second pic. I included that one just to show the tree species). I will cut off the blackened branch and keep my eye on the brown.

I'm now noticing some other smaller brown areas on some of the other green giants. Is that just normal for this tree? It's still warm here in sc.

Google "Sooty mold on arborvitaes"

Sooty mold is not that localized and uniform.

i suspected it wasn't from your height challenged dog.. lol ...

but the remedy does not change ... snip out the black stuff and dispose of it.. job done ...

but other than deny the dog scenario.. you didnt really answer any of our questions ...

how localized is it ...

a conifer that grew 3 feet in a season is not really suffering.. so i dont know why you would resort to anything other than clipping out a few pieces ...

its just not a chem thing.. IMHO

ken