Scale insects are common and often frustrating-to-manage insect pests of ornamental trees and shrubs. There are also many different kinds (Families) of scales, in addition to a large number of species of scale insect pests of important host plants in our landscapes. In some cases, scale insects from the Family Coccidae (Soft Scales) may be less challenging to manage than the armored scales. However, that is not always the case. Soft scale species discussed elsewhere in further detail in this Guide include:
Coccidae (Soft Scales)
- Eulecanium spp., Parthenolecanium spp. and others - lecanium scales
- Neolecanium cornuparvum - magnolia scale
- Neopulvinaria innumerabilis (formerly Pulvinaria innumerabilis) or Pulvinaria acericola - cottony maple scales
- Parthenolecanium fletcheri - Fletcher scale
- Parthenolecanium quercifex - oak lecanium scale
- Physokermes hemicryphus - spruce bud scale
- Pulvinaria floccifera - cottony camellia scale/cottony taxus scale
- Toumeyella liriodendri - tuliptree scale
- Toumeyella parvicornis - pine tortoise scale
See individual entries for each species within this Guide for further details and specifics.
Damage to the host plant depends upon the species of scale insect and possibly also the host plant involved. Scales, in general, can cause discoloration of the foliage, needle or leaf loss, chlorosis, dieback, and even host plant mortality. See each individual species entry for further details.
See each individual species entry for further information. Monitoring times (during the season) vary depending upon scale species. Crawlers may be active at different times of year, or overlapping generations may be present. Additionally, symptoms of scale infestation may be slightly different depending upon the species of scale or host plant involved. See each individual species entry for further details.
Trees under drought stress in managed landscapes or urban forests may have more trouble with scale infestations than those without stress. Practices such as adequate watering during these times may help support tree health and reduce additional stressors. Prune and remove and destroy heavily infested branches if possible without compromising tree shape or health. Some soft scales are large enough to remove from host plants (when practical) with a soft brush. See each individual species entry for further details.
Parasitoid wasps, lady beetle and other insect predators, pathogens, and certain abiotic conditions as well as competition can influence scale populations. See each individual species entry for further details.
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)
See individual scale species for specific management options.
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.
