We purchased & planted 22 4’ arborvitae’s last fall. We did everything the Hewitts people told us to do, and they looked beautiful. Now they all have black patches that look terrible. We clipped out as much as possible, but now they look scraggly. This was a very expensive project & I’ll be crushed if they die. Please HELP!
The black patches are likely a fungal disease. There is not spray to control it. Continue to trim out the blacked patches and feed them with Espoma Tree-Tone to help them recover. This is likely due to the rainy late summer and fall weather. Another possibility is that they were buried too deep of mulch was piled up against the bark. Get down under the plants and brush away any mulch or soil until you find the original soil that the arbs came in and push it away from the crown and bark of the plant a few inches and keep it that way. Dirt of mulch piled against the bark of the plants slows or stops the flow of nutrients up from the roots to the branches and foliage above. Basically it slowly strangles the plant weakening them and making them more susceptible to these disease problems.