4 (1 = rare 5 = annual)

5 (1 = very little damage 5 = plants killed)

Oystershell scale attacks a wide range of plants.

• Common Privet (Ligustrum vulgare)

Shrub

• Common Lilac (Syringa vulgaris)
• Redosier Dogwood (Cornus sericea or Cornus stolonifera)

Tree

• Asian White Birch (Betula platyphylla)
• Chinese Elm, Lacebark Elm (Ulmus parvifolia)
• Crabapple (Malus species and hybrids)
• European Mountainash (Sorbus aucuparia)
• Green Ash (Fraxinus pennsylvanica)
• Silver Maple (Acer saccharinum)
• White Ash (Fraxinus americana)
• White Willow (Salix alba)

Tree Fruit

• Apple (Malus pumila)

The scale got its name because it resembles an oyster shell. It is found in every state but it is found more often and in heavier numbers in the northern states. The scale often blends in with the color of the plant's bark. The scale is often "discovered' because branches are dying back from the feeding injury.

Oystershell scale is an armored scale (its covering is a hardened waxy material). There are two commonly found races of oystershell scale in Illinois. They are brown oystershell scale and gray ostershell scale. The scale overwinters as eggs under the mother's covering. Crawlers of the brown race occur on dogwood when Vanhoutte spirea is in full bloom (about mid June in Northern Illinois). The crawlers of the gray race, which feeds on other hosts, emerge later.

Crawler sprays of chemical insecticides timed to coincide with egg hatch are effective. This insect is not controlled with dormant oil applications. Pruning severely damaged areas will reduce infestations.

Home, Yard & Garden Pest Guide
The Home, Yard & Garden Pest Guide (C1391) provides is written for homeowners and other residents and provides nonchemical and current chemical recommendations for controlling pests associated with trees, shrubs, turf, flowers, groundcovers, vegetables, fruit, and houses. In addition, you'll find detailed information about integrated pest management, pesticide safety, and pesticide application and calibration techniques. This publication may be purchased at your local University of Illinois Extension Unit office, or by calling 800-345-6087, or by placing an order online (search for "C1391").
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Illinois Commercial Landscape and Turfgrass Pest Management Handbook
The Illinois Commercial Landscape and Turfgrass Pest Management Handbook (ICLT) is written for professional applicators and provides nonchemical and current chemical recommendations as well as application timing information for all major pests of turf, woody ornamentals and herbaceous ornamentals. This publication may be purchased at your local University of Illinois Extension Unit office, or by calling 800-345-6087, or by placing an order online (search for "ICLT").
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U of IL - Distance Diagnosis through Digital Imaging
A free plant, weed, insect and disease identification service available through your local University of Illinois Extension office. Center Educators or State Specialists review & respond to information and digital images submitted by local Extension office personnel. Some samples may require further examination or culture work (nominal fee involved) at the U of IL Plant Clinic.
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U of IL - Plant Clinic
Services include plant and insect identification, diagnosis of disease, insect, weed and chemical injury (chemical injury on field crops only), nematode assays, and help with nutrient related problems, as well as recommendations involving these diagnoses. Microscopic examinations, laboratory culturing, virus assays, and nematode assays are some of the techniques used in the clinic.
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