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Parthenolecanium corni

European fruit lecanium scales. Photo: Lacy L. Hyche, Auburn University, Bugwood.
Scientific Name: 
Parthenolecanium corni
Common Name: 
European Fruit Lecanium
Growing Degree Days (GDD's): 
35-145 GDD's (mid-April to early-May for dormant), 1266-1645 GDD's (end of July) for foliar, Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name): 
Alder (Alnus spp.)
American elm (Ulmus americana) 
Apple (Malus spp.)
Basswood (Tilia spp.)
Birch (Betula spp.)
Cherry (Prunus spp.) *Preferred host.
Cotoneaster (Cotoneaster spp.)
Dogwood (Cornus spp.)
Elderberry (Sambucus spp.)
Gleditsia (Honey Locust)
Holly (Ilex spp.)
Hornbeam (Carpinus spp.)
Maple (Acer spp.) *Preferred host.
Mulberry (Morus spp.)
Oak (Quercus spp.)
Peach (Prunus spp.) *Preferred host.
Pear (Pyrus spp.)
Plum (Prunus spp.) *Preferred host.
Poplar (Populus spp.)
Redbud (Cercis spp.)
Smoketree (Cotinus coggygria)
Sweetgum (Liquidambar styraciflua)
Sycamore (Platanus spp.)
Viburnum (Viburnum spp.)
Willow (Salix spp.)
Insect Description: 

This soft scale has an erroneous common name, given that it is native. It is considered to be one of the most common and potentially abundant soft scale species in its geographic range. It also has a very wide host range and can be found on perhaps any shade or fruit tree, shrub, or other woody ornamental plant (many in addition to what is listed above). This scale is also known to vary widely in shape and form, making identification (and distinction from other lecanium scales) difficult. For example, on the basis of structural/physical characteristics, it is very easily confused with fletcher and oak lecanium scales (Parthenolecanium fletcheri and P. quercifex, respectively). As such, all three are historically referred to as a species complex. Adult female European fruit lecanium scales are approximately 1/4 inch in length and although variable in shape, can possess two swollen areas on the dorsal (back) side of the insect. Color may vary from reddish brown to brown with black markings. Crawlers, or the mobile immature stage of the insect, are first white in color and change to yellow as they mature and found settled on the undersides of leaves near the veins. Male scales are different in shape and color from the females, with adult males being tiny fly-like insects with delicate wings. Second instar nymphs (immatures) are said to overwinter on the bark of host plants. These overwintered nymphs mature and begin to feed in the spring, and once mature the males emerge and mate with the females, roughly around mid-May. At a point in May or early June, females lay tiny white eggs that are hidden beneath their bodies. Each individual female may be capable of laying approximately 950 to 3,000 eggs. Reportedly, the number of eggs laid may vary with host. Eggs then hatch in approximately 20-30 days and crawlers disperse to the underside of leaves, where they begin to feed. Nymphs remain there until the fall, at which point they move to the bark of small twigs and branches to overwinter. One generation per year is reported in most locations.

Damage to Host: 

The European fruit lecanium feeds by inserting piercing-sucking mouthparts into the host plant to remove fluids. Moderate or heavy infestations of this soft scale will lead to the production of honeydew, which can attract stinging insects and support the growth of sooty mold. Heavy or prolonged infestations can cause leaf drop, stunted growth, and twig dieback, especially following maturation of the females and associated feeding in mid-spring into early summer. Young trees growing with poor site conditions, or newly transplanted trees may be the most susceptible. 


The presence of honeydew or sooty mold may be monitored for, beginning in late May. Monitor for swelling and maturing females on host plant twigs. Monitor for crawlers (with magnification) on the undersides of leaves. In heavy infestations, stunted growth, leaf yellowing, and twig dieback (especially in the presence of honeydew and sooty mold) may signal an infestation of this soft scale, so check twigs for mature or maturing females.

Cultural Management: 

Plant trees and shrubs at sites with characteristics appropriate to their success. Choose the right plant for the right site, prioritizing long-term plant health and vigor. These choices will help prevent issues with native insect pests in the future, as they typically seek to use hosts that are ailing due to other abiotic and biotic stressors. Note that ants may protect soft scales from parasitoids and predators, in order to benefit from their honeydew. Heavily infested branches may be pruned out and removed to help reduce the number of scales on a single plant.

Natural Enemies & Biological Control: 

As a native insect, multiple natural enemies are reported for this species. If a heavy population of P. corni is detected and cannot be tolerated, first select reduced risk chemical management options that will preserve natural enemies.  Some examples include Blastothrix spp. (a chalcid wasp parasitoid; Agwoska, 1987 and Blahutiak, 1973), and multiple species of parasitic wasps in the following families: Aphelinidae, Encyrtidae, and Pteromalidae. Additional other predators and parasitoids of European fruit lecanium are also found in the families: Anthribidae, Chamaemyiidae, Chrysopidae, Coccinellidae, and Noctuidae (Source: Scalenet).

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)

Malathion (L)

Neem oil (NL)

Pyrethrin+sulfur (NL)

Pyriproxyfen (eggs) (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.

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: .