Carulaspis juniperi

Juniper scale, multiple life stages. Photo: Lorraine Graney, Bartlett Tree Experts, Bugwood.
Scientific Name: Carulaspis juniperi
Common Name: Juniper Scale
Growing Degree Days (GDD's): 22-148 GDD's (dormant), 707-1260 (crawlers), Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension.) 450–600 approx. (crawlers), Base 50F, March 1st Start Date (Source: Robert Childs, UMass Extension.)
Host Plant(s) Common Name (Scientific Name)
Arborvitae (Thuja spp.)
Cypress (Cupressus spp.)
False cypress (Chamaecyparis spp.)
Juniper (Juniperus spp.) *Most commonly collected on this host. (Miller and Davidson, 2005)
Leyland cypress (Cupressus x leylandii)
Pfitzer juniper (Juniperus x pfitzeriana)
Savin juniper (Juniperus sabina)
Yew (Taxus spp.)
Insect Description:

The juniper scale is native to Europe and is now found throughout the United States. Female juniper scales have covers (tests) that are circular, white, and approximately 1.5 mm. in diameter. Male scales are smaller, oval/elongate, and white. Adult males are orange, winged insects (present in mid-July and late-August in Ohio). In most of the range of this scale in the US, there is a single generation per year. However, in warmer climates, 2 annual generations may be possible. The overwintering life stage are adult females, which can be found on the needles of the host plant, filled with yellow eggs. By late May or early June (in Connecticut, New Jersey, and Ohio) crawlers appear. Over the next approximately 30-45 days, egg laying and crawler emergence is possible. May be confused with the minute cypress scale (Carulaspis minima). 
Damage to Host:

Light infestation may produce no noticeable symptoms. The first signs of infestation may include: loss of normal "lustrous" color of the healthy host, infested foliage failing to develop new growth, and off-color appearance to the tree or shrub. This pest causes yellowed foliage and needle drop. It can eventually kill the host plant, if infestations are heavy enough (10 or more scales per 1/2 inch of branch). Scales often not noticed, due to small size, until chlorosis is very apparent. Additional host plants are listed on ScaleNet in the Cupressaceae, Pinaceae, and Taxaceae families in at least 17 different genera. 
Monitoring:

Monitor susceptible host plants for off-color foliage. Examine needles using magnification (10X hand lens) for tiny, circular, white scale covers. Observe scale covers for the evidence of natural enemy activity (ex. exit holes from parasitoids). If natural enemies are present, and chemical management is deemed necessary, choose reduced risk insecticide options in order to preserve natural enemies. Avoid chemical applications when natural enemies are abundant, if at all possible. The timing of egg hatch and crawler emergence and corresponding growing degree days are debated. Over a 3-year study in Kentucky, egg hatch was reported with a base 45F at 987 GDD's in 1992, 799 GDD's in 1993, and 791 GDD's in 1994 (Mussey and Potter, 1997). This same study found that the egg hatch of juniper scale may be much more accurately timed when 95% bloom of Ilex opaca (American holly) and Cladrastis kentuckea (American yellowwood) has occurred. 
Cultural Management:

Avoid planting hosts next to buildings, as this can create favorable environmental conditions for juniper scales. If possible, prune out and destroy heavily infested branches. 
Natural Enemies & Biological Control:

Juniper scales have a long list of natural enemies. At least 13 families and 20 genera are implicated as being enemies of this scale (ScaleNet). This includes parasitic wasps (ex. Encarsia citrina), mites, predaceous lady beetles (ex. Chilocorus distigma), dustywings (ex. Aleuropteryx juniperi), and certain sap beetles. This species of scale may also be killed by winter temperatures, past research finding 13% - 85% winter mortality. 
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)

Malathion (L)

Neem oil (NL)

Pyrethrin + sulfur (NL)

Pyriproxyfen (L)

Spinetoram + sulfoxaflor (N)
Notes:

Oils have been effective at managing this scale using both dormant and verdant treatments (Cornell Cooperative Extension). 

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).

When used in a nursery setting, chlorpyrifos is for quarantine use only.

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".