Cryptococcus fagisuga

Beech scale on American beech. Photo: Tawny Simisky
Scientific Name: 
Cryptococcus fagisuga
Common Name: 
Beech Scale
Growing Degree Days (GDD's): 
None available at this time.
Host Plant(s) Common Name (Scientific Name): 
American Beech (Fagus grandifolia) *Preferred host in North America.
Beech (Fagus spp.)
European Beech (Fagus sylvatica) *Not thought to be heavily attacked.
Oriental Beech (Fagus orientalis)
Insect Description: 

This is a non-native scale insect whose population in North America consists of only females. Adult females are capable of reproducing without a male. The females are a light yellow color, tiny (less than 1 mm. in size), and wingless. The body of the female can be covered with white, woolly material that in large populations can coat the tree. Females will lay tiny, yellow eggs within their woolly mess which will hatch into the nymphs or crawlers which disperse through their own movement locally on the tree or to new host plants by the wind. Crawlers will settle and insert their piercing-sucking mouthparts into the tree to feed. One generation occurs per year. A huge population of this insect can develop on a tree in 2-3 years (Johnson and Lyon, 1991).

Damage to Host: 

This scale by itself is not very damaging, but its feeding allows two species of fungi (Neonectria faginata and Neonectria ditissima) to enter the host, and the combination can be lethal to the tree. Collectively, this species complex is known as Beech Bark Disease. The bark and trunk of host trees are impacted. Once the fungus has entered the host plant, it is not easily managed and success varies. As the fungus kills and cracks the bark of the tree and the outer wood rots, American beech trees look swollen and lumpy and clearly diseased compared to the smooth bark of a healthy host. Hosts of this scale include native and introduced beeches (Fagus spp.). Some individual American beech have exhibited resistance to Beech Bark Disease.

Monitoring: 

When looking for the beech scale, search the bark of the main trunk and branches for white, woolly material produced by the scales in any cracks and crevices. Red-pink/salmon colored fruiting bodies might be the first signs of the fungi that are noticed. Tarry, black spots on the bark might also indicate fungal infection.

Cultural Management: 

Scales may be removed from the bark of individual trees with a soft brush, however this may not be practical. Beech bark disease is currently widespread in Massachusetts, so it is only a matter of time before ornamental American beech planted in landscapes become infected. Planting European beech in landscapes is a good option for preventing issues with this insect and disease complex. 

Natural Enemies & Biological Control: 

Certain lady beetles can be predators of this scale insect, but may not eliminate beech scale populations. The twice-stabbed lady beetle (Chilocorus stigma) is a common predator of beech scales, however research suggests that they are not able to control the population of this insect. At least four species of mite was also noted as predators of the beech scale (Mayer and Allen, 1983).

Chemical Management: 

For crawlers:

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: January 2024. To check current product registrations in Massachusetts, please visit: https://www.mass.gov/pesticide-product-registration .