Adult female gloomy scales appear covered with a convex, circular, and brown to gray armored coating (test) and are approximately 1/8 of an inch in diameter. Adult males have similar covers, but may be elongate. Both are black when rubbed. The body of the adult female, hidden beneath this covering, is pink or purple. Eggs of this insect are faint pink in color and the crawlers (mobile immature stage) are cream colored. This armored scale insect is found on the bark of its host plants. One generation per year has been reported in Maryland. Fertilized females reportedly overwinter. Egg laying is observed in early July and continues through August. Eggs hatch almost immediately, and pale straw-yellow crawlers are also present during this time frame. Winged adult males are reported from mid-August to mid-September. This is a native scale insect that has been reported from much of the eastern US. In the field, this scale may be confused for the obscure scale (Melanaspis obscura) which is similar in appearance, with the exception that obscure scales favor oaks (Quercus spp.).
Red and silver maples may be the most impacted. Reports of the activity of this insect range from a significant pest that may lead to tree mortality to an occasional pest. This insect occurs primarily in the eastern US, and has been reported as far north as New York. Scales typically settle on 1 to 4 year old branches. Heavy infestations cause stunting and dieback. Some report that street trees are more significantly impacted by this insect.
While this insect has been reported only as far north as NY, it is likely that it is easy to transport gloomy scales (like many other scale insects) on infested nursery stock. Johnson and Lyon (1991) report that trees in nurseries as well as landscaped settings are frequently injured by this insect, but that it is a primary pest of silver and red maples. Miller and Davidson (1990) consider this insect to only be an occasional pest. Look for gloomy scales on the bark of branches. Convex, gray scale covers of the immatures may be seen in the winter. Adult female scale covers may be noticeable in the summer months.
If practical and the scales are limited to individual branches, prune and remove them to help reduce the scale population.
The gloomy scale has been reported as a host for the parasitoid wasps, Encarsia citrina as well as Thysanus nigrellus. A fungus also reportedly impacts these scales, Cosmospora flammea.
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 (L)
Spinetoram + sulfoxaflor (N)
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.
