Thank you for reaching out to Ask Extension with your question about arborvitae tree leaves that are turning brown.

Arborvitae are popular landscape trees that can add beauty and privacy to your property, but there are several reasons why the leaves on these trees can turn brown and wither. A failure to thrive may result from excessive watering, adverse weather conditions such as wind or summer drought, and damage when the trees were planted or later root injury. Unfortunately, arborvitae and other evergreen trees tend to exhibit symptoms of stress and dieback some time after the damage takes place, which may make identifying the cause challenging. In the case of drought, which you suspected may have contributed to your arborvitae leaves browning, trees and shrubs can be damaged over multiple seasons, eventually lead to death.

Insects that can harm arborvitae include bagworm, arborvitae leafminer, and spruce spidermite, with bagworm being the most prevalent arborvitae pest. Arborvitae can also be adversely affected by diseases such as cedar leaf blight, fungal tip blight, and root rot.

Unfortunately, two arborvitae shown in the photograph you provided exhibit extensive foliage browning and are unlikely to recover.

Hiring an arborist, who has received specific training and passed a certification exam, can visit your property, evaluate the area and make a diagnosis after considering details of your situation which may not be obvious from the photo you provided. Use this link to connect with a certified arborist in your area.

I have provided some links below to learn more about arborvitae care and problems that these trees can experience:

www.extension.psu.edu/the-mighty-arborvitae

www.extension.umd.edu/resource/what-causes-trees-and-shrubs-to-die/

www.extension.purdue.edu/extmedia/id/id-477-w.pdf

Please reach out again if you have additional questions or concerns.