The Reason Why Arborvitae Foliage Turns Brown . The trees are 10 to 12 feet tall and seem to be doing well, except for the side facing the road. As with most trees, arborvitae are used to climate changes and will acclimate to lower temperatures. These trees get surrounded by a lot of snow. The trees are small right now, about 2 1/2 to 3 foot tall. Since arborvitae are so green, many people forget to water their newly planted trees. Last fall, we planted a staggered row of arborvitae along the road as a natural fence line about 4 to 6 feet from the road. A neighbor lost a small evergreen shrub recently from what looked to me to be disease or insect damage which has me concerned. Sometime ago, you mentioned the salt on the roads during the winter posing a problem. New trees need to be watered deeply for the entire first season after planting. These arborvitae diseases mostly emerge in the rainy season. Browning on arborvitae leaves can occur at various times of the year. Recently, we noticed that one of them looks pretty much dead and the one next to it is heading there. I noticed that my dog urinates on them? Sorry I couldn't be any more descriptive but any help about what flying insects might be attracted to these would be helpful. They are the variety that is supposed to grow either 10 or 15 feet I think, not the really huge ones. Last year there was a small amount of leaf loss due to snow. Winter sun, wind and cold temperatures can bleach and dry out evergreen foliage, damage bark and injure or kill branches and roots. Road Salt Damage to Arborvitae. Could this be killing them? Sprinklers never work as well as a deep soak. We planted 10 Arborvitae's. The disease produces fungus, which is traveled within the tree through the rain water pours thereby, creating an infection in the bark of the tree and kills the defensive tissues of the arborvitae by germinating them. Arborvitae (Thuja spp.) includes five species of coniferous evergreen trees and shrubs used widely in landscaping to add winter color. However, if a sudden cold spell hits the tree before it is done adjusting, the weather can freeze the plant tissues and make your tree sickly or kill it completely. When it happens in summer, the color change could be happening because of drought.But if your arborvitae shrub turns brown in winter or early spring, the likely reason is winter burn. The best way to achieve this is simply to turn your hose on and leave the open end at the base of your tree for 10 minutes every few days in the hot summer. This may be true even for well-established trees.