By: Jean Ferdinandsen, Certified Arborist
Arborvitae or white cedar (Thuja spp.) are a common and valued evergreen in our Wisconsin landscape. They are often used for screening purposes. All arborvitae have evergreen, scale-like leaves arranged in flat sprays and small dried capsules as fruits.
If the foliage on your arborvitae appears to be stippled, bleached, or bronzed, spruce spider mites may be the culprit. These tiny creatures destroy the chlorophyll-bearing cells using needle-sharp mouthparts to feed. Severely affected foliage often turns brown and drops off as a result of mite injury. Heavy attacks can cause branch dieback or death. Dust, pollen and shed foliage may accumulate in tiny strands of webbing that form. This collection of debris adds to the unhealthy appearance of trees and favors the increase in mite populations.
A few mites are often not a cause for concern, but larger populations may warrant control. Mite injury is most obvious when the first hot dry spells of summer come. This is usually when the maximum damage has already occurred. Hot, dry weather also predisposes trees to attack.
Healthy, vigorous trees are less subject to attack. Be sure to maintain proper moisture, fertility, and mulch to minimize stress.
Wachtel Tree Science & Service has trained diagnosticians and Certified Arborists to help you determine if spruce spider mites are damaging your arborvitae (or other evergreens) and to provide treatment recommendations. It is best to have mite damage properly diagnosed before treatment. Improper insecticide use can result in large and destructive populations of mites. This is because pesticides kill the natural enemies of spider mites without controlling the mites themselves.
If you suspect mite damage, give Wachtel Tree Science & Service a call so that the presence of mites can be confirmed and corrective action taken if warranted. Damage from spruce spider mites can often be confused with such things as leaf miner, winter damage, or seasonal needle drop. Have our professionals help you determine for sure.
© Copyright 2003 – Wachtel Tree Science & Service, Inc.