Oystershell Scale: Identify & Control

Oysters on your trees? This is not the water-dwelling creature but a pest known as oysterscale. Oysterscale, or mussel scale, resides in the family of what is known as scale insects that commonly affect trees and shrubs around the country.

Up Next: What Is Not Killing Your Trees?

This pest can be very harmful to trees if left untreated. Identifying and controlling oysterscale will go a long way in keeping your trees healthy.

oystershell scale
A. Steven Munson, USDA Forest Service, Bugwood.org

Look For Oyster Shell-Like Scale Covering Branches

Oytstershell scale is caused by a scale insect, not a fungus. Oystershell adults excrete a waxy cover that gives it is oyster-like appearance. This cover protects the insect’s eggs throughout the winter. Eggs hatch from mid-to late April and crawlers are active into early May.

Symptoms Result In Reduced Tree Vigor & Health

Another sign that your trees may be suffering from oystershell scale is reduced tree vigor and health:

  • Wilting leaves
  • Dieback
  • Premature leaf drop

These symptoms are often signs of a heavy infestation and can also be an indication of other pests or diseases. Keep an eye on your trees and contact an ISA-certified arborist if you notice worrying symptoms.

Controlling & Preventing Oysterscale In Your Trees

After oysterscale has established itself, horticultural oils cannot kill the pest. Rather, they can be carefully scraped off in the winter and placed in a bucket of hot soapy water to kill the parent scales. In the spring, horticultural oils can be sprayed by a professional to smother the insects. Pruning is also an effective method of controlling oysterscale, when needed.

Before self-treating your trees, contact an ISA-certified arborist from Hansen’s Tree Service for a hassle-free consultation. Hansen’s will inspect your trees and provide a diagnosis and treatment.

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