Hemiberlesia (formerly Abgrallaspis) ithacae

Hemlock scales on Abies balsamea. Note the uncovered female. Photo: Tawny Simisky, UMass Extension.
Scientific Name: 
Hemiberlesia (formerly Abgrallaspis) ithacae
Common Name: 
Hemlock Scale
Growing Degree Days (GDD's): 
35-121 GDD's (dormant), 1388-2154 GDD's, Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name): 
Douglas-fir (Pseudotsuga spp.)
Fir (Abies spp.)
Hemlock (Tsuga spp.) *Preferred host.
Pine (Pinus spp.)
Spruce (Picea spp.)
Insect Description: 

The hemlock scale is a native armored, circular shaped scale insect that may be found on eastern hemlock as well as the additional hosts listed above. This scale insect uses piercing sucking mouthparts to remove host plant fluids from the underside of host plant needles. The upper needle may have a small yellow spot as an initial sign of feeding by this insect. Female hemlock scale tests are dark brown-gray, circular to oval, and approximately 2 mm in diameter. Male hemlock scales have elongate oval covers that are blackish in color. Winged males occur in this species. The body of the female is yellow-green in color and eggs are a pale yellow. Two generations per year have been reported in Maryland. Eggs produced by the females of the first generation may hatch in June, maturing by late July, and producing second generation eggs in August and September. Second generation crawlers may settle on the needles, overwintering in the second instar. 

Damage to Host: 

Yellow spots may be seen on the upper surface of infested needles. When 4-6 scales are present per needle, the needles may yellow and drop from the host plant (Johnson and Lyon, 1991). Dieback of branches and defoliation of trees has been reported (Miller and Davidson, 2005).

Monitoring: 

Look for armored, circular shaped, brown or dark colored scales on the underside of needles. Do not confuse with the elongate hemlock scale (Fiorinia externa) or the introduced shortneedle evergreen scale on hemlock and other conifers, Dynaspidiotus tsugae. 

Cultural Management: 

Remove and destroy infested branches when practical. 

Natural Enemies & Biological Control: 

Important wasp parasitoids have been reported in Maryland on this species and are observed to emerge in that state in April, June, July, and again in August. Preserve and protect natural enemies.

Chemical Management: 

Abamectin (NL)

Acephate (NL)

Acetamiprid (L)

Azadirachtin (NL)

Buprofezin (NL)

Carbaryl (L)

Chlorpyrifos (N)

Clothianidin (NL)

Cyantraniliprole (NL)

Cyfluthrin (NL)

Dinotefuran (NL)

Gamma-cyhalothrin (L)

Horticultural oil (L)

Imidacloprid (L)

Insecticidal soap (NL)

Lambda-cyhalothrin (L)

Neem oil (NL)

Pyrethrin + sulfur (NL)

Pyriproxyfen (eggs) (L)

Spinetoram + sulfoxaflor (N)

Notes: 

Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), acetamiprid (injection), azadirachtin (injection, soil drench), clothianidin (soil drench), cyantraniliprole (soil drench, soil injection), dinotefuran (soil drench), imidacloprid (soil drench), and neem oil (soil drench).

Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.

Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.

Read and follow all label instructions for safety and proper use. If this guide contradicts language on the label, follow the most up-to-date instructions on the product label. Always confirm that the site you wish to treat and the pest you wish to manage are on the label before using any pesticide. Read the full disclaimer. Active ingredients labeled "L" indicate some products containing the active ingredient are labeled for landscape uses on trees or shrubs. Active ingredients labeled "N" indicate some products containing the active ingredient are labeled for use in nurseries. Always confirm allowable uses on product labels. This active ingredient list is based on what was registered for use in Massachusetts at the time of publication. This information changes rapidly and may not be up to date. If you are viewing this information from another state, check with your local Extension Service and State Pesticide Program for local uses and regulations. Active ingredient lists were last updated: September 27, 2024. To check current product registrations in Massachusetts, please visit the MA Department of Agricultural Resources Pesticide Product Registration page and click on "Search Pesticide Products Registered in Massachusetts - Kelly Solutions".