Asterodiaspis variolosa

Golden oak scales. Photo: United States National Collection of Scale Insects Photographs, USDA Agricultural Research Service, Bugwood.
Scientific Name: Asterodiaspis variolosa
Common Name: Golden Oak Scale
Growing Degree Days (GDD's): 7-121 GDD's (dormant), 802–1266 GDD's (crawlers), Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name)
Chestnut oak (Quercus montana)
English oak (Quercus robur)
Kermes oak (Quercus coccifera)
Oak (Quercus spp.)
Sessile oak (Quercus petraea)
White oak (Quercus alba) *Preferred host.
Insect Description:

The golden oak scale is one of at least three closely related species that are found on the twigs of oak in the eastern (and western) United States. The scientific name of the golden oak scale, as is the case with many insects, has changed over time. In past literature, it may be found under Asterolecanium variolosum or other variations. In the field, the appearance, life cycle, and host plant preferences of the group of closely related species is so similar that Johnson and Lyon (1991) argue that accurate species identification may not be necessary when making management decisions. The populations of this insect are primarily female, and males are either rare or not described. Circular-shaped females vary in size from 1 to 2 mm. (0.04-0.08 inches) and may be golden, greenish, or brown in color. The golden oak scale may also be known as a pit-making scale, due to the fact that the insects are often found in tiny depressions made in the twig as a result of the feeding of the insects. The bark around this pit may also be slightly swollen. Mature females overwinter and produce living young (crawlers) which are observed in the spring and summer months. Females have been observed to produce young for up to 5 months. Crawlers are not thought to disperse far from the female and often colonize the same current season or 1 year old twigs. Golden oak scales feed using piercing sucking mouthparts to remove host plant fluids. One generation per year is reported.
Damage to Host:

This pit-making scale may cause twig die-back as a result of feeding. Poor growth may be observed. Dieback is first noticeable in the summer or fall and the affected branches or twigs may retain their dead leaves throughout the winter. Severe infestations of this scale have been observed to delay leaf growth of infested hosts in the spring. Young trees may be killed by this scale when repeated, heavy infestations occur yearly. The golden oak scale has been observed to co-occur with anthracnose fungi on oak in the eastern US, which, when combined, is particularly stressful to host plants.
Monitoring:

Current year’s growth and 1-year-old twigs of host plants. Look for pits and circularly shaped scales, especially in areas where dieback may be noticed. If anthracnose damage on white oak is noticed, also monitor for the presence of the golden oak scale.
Natural Enemies & Biological Control:

The parasitic wasps Habrolepis dalmanni and Metaphycus asterolecanii have been reported in golden oak scale populations. In closely related species of scale, H. dalmanni is reported to parasitize up to 20% of their populations. However, the efficacy of these natural enemies at managing Asterodiaspis variolosa populations is not fully understood.
Chemical Management:

Abamectin (NL)

Acephate (NL)

Acetamiprid (L)

Azadirachtin (NL)

Buprofezin (NL)

Carbaryl (L)

Chlorpyrifos (N)

Clothianidin (NL)

Cyantraniliprole (NL)

Cyfluthrin (NL)

Dinotefuran (NL)

Flonicamid+cyclaniliprole (N)

Gamma-cyhalothrin (L)

Horticultural oil (L)

Imidacloprid (L)

Insecticidal soap (NL)

Lambda-cyhalothrin (L)

Neem oil (NL)

Pyrethrin + sulfur (NL)

Pyriproxyfen (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".