What Is Wrong With My Arborvitae?

Do the twigs and leaves turn brown during a drought?

Does the foliage browns, trunk splits near the soil?

Is the plant defoliated, branches bear cocoonlike bags on them?

Are the leaves turning gray or brown and the foliage is webbed?

Are the leaves wrinkled and discolored?

Is there sawdust at the base of the plant and the growth is poor?

Are the leaves yellow, stems, and leaves are covered by small bumps?

Are the leaf margins notched?

Do the twig tips or leaves turn brown or yellow and die back?

Is the lower foliage burned?

Does the plant loses its shape?

A shortage of water in summer may cause twigs to turn brown and eventually drop off. During the summer, soak the soil to a depth of about two feet once every two weeks or so. If the symptoms develop in late winter or early spring, they may be caused by drying winds and hot sun. Minimize damage by mulching and thoroughly soaking the ground around the shrubs before the ground freezes in winter.

Browning foliage and splitting trunk usually indicate a freezing injury. Normally arborvitae gradually acclimates to increasing colder temperatures, but in some cases, a prolonged warm fall, followed by a sudden cold spell prevents normal gradual acclimatization and plant tissues freeze and die. Avoid feeding with high nitrogen fertilizers late in the season and be sure that arborvitaes are planted in well-drained soil.

Bagworms are causing these symptoms. They are small, brown caterpillars that feed on inside the silky, white bags they create. Handpick and destroy all the bags. If you notice crawling caterpillars you may have to use insecticide as they are really hard to get rid of.

Spruce spider mites or red spider mites spin webs and cause a graying or browning of arborvitae leaves. You can control spider mites by spraying plants thoroughly with water 2-3 times a day for several days. For severe infestations, spray plants with insecticidal soap.

Wrinkled and discolored leaves on arborvitae shrub usually indicate aphids. The arborvitae aphid is a reddish-brown, soft-bodied, pear-shaped sucking insect about the size of the head of a pin. You can control them by washing them off the plant with water spray. Introducing ladybugs will keep their number low. Insecticidal soap or neem oil should be used with severe infestations.

In its larval stage, the Cedar Tree Borer bores into the inner bark and wood, frequently girdling the arborvitae, making it more susceptible to heat, drought, and disease. A mass of gummy sawdust at the base of an injured arborvitae shrub signals the presence of borers. If you see borer holes in your trees, probe into them with a flexible wire or inject a solution of parasitic nematodes.

Scales can often be seen infesting arborvitae shrubs. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying dormant oil just before the growing season.

Notched edges on the leaves are caused by Arborvitae weevils. The wingless, black bugs covered with metallic green scales are adults that feed on the leaves. To control them, spread a drop cloth around your plant and shake it so the adults drop. You can get rid of them after that. Spray leaves several times with pyrethrin for major infestations.

Various fungal diseases attack arborvitae shrubs. These diseases mostly attack foliage or shrubs already weakened by stress from heat, lack of water, or other environmental problems. Sometimes the entire shrub may be involved. Spray plants with sulfur to prevent fungal diseases from spreading, especially if the weather is wet. Prevent problems by thinning to provide good air circulation.

Dog urine may discolor foliage and even kill branches of low growing plants along property borders. Spraying foliage with an anti transpirant gives some protection. Screen target plants or spray them with an aerosol pet repellant.

Old arborvitae shrubs can easily be damaged by harsh weather and generally have difficulties recovering. If pruning does not improve the shrub's appearance it may be time to replace it.

If the shrub is dropping leaves in spring or fall it's due to normal leaf senescence. All evergreens drop some of their foliage every year, usually in the fall, but it can occur in the spring as well. Do not be concerned if you notice some brown, dead leaves on arborvitaes at the same time the deciduous trees and shrubs are displaying their fall colors.