Arb needles turn yellow when they die. They are evergreens. As they age they do loose some needles in the interior, but yellowing at the tips is a sign of trouble. If you watered them every day throughout the fall, you may have overwatered them. If they had a fungal disease you should see black spots on the needles. It is not a soil borne disease. Best And Happy Yardening, Nancy.
Arborvitae Needles Turning Yellow
Question From: S. DeLuzio - CONNECTICUT
Q: I had several Arborvitaes planted in my yard last fall. I watered them up until the first frost of the season, per the instructions of the landscaper who planted them. There were a few days with heavy soaking rain, which I skipped the watering so that I didn't end up over watering them. Over the late fall/winter months, the leaves began to turn a brownish yellow. I figured the tree just was turning colors as most other trees do in the fall. However, it is now late April and the leaves have not returned to their normal green color. We live in Connecticut, which was hit by especially hard weather (Hurricane Sandy - October 2012), and a large winter storm a couple months ago, which dropped about 3 ft. of heavy snow. Could there be a disease, or other environmental factor that caused this to happen? If so, is there any hope that the trees will return to their normal green color? If the trees were killed by a disease, is it possible that the disease would be in the soil? My concern is that if we replace them that any future trees may also be damaged.