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Parthenolecanium fletcheri (soft scale)

Fletcher scale. Photo: Tawny Simisky
Scientific Name: 
Parthenolecanium fletcheri (soft scale)
Common Name: 
Fletcher Scale
Growing Degree Days (GDD's): 
38-148 GDD's (overwintered nymphs); 1029-1388 GDD's (crawlers); 2515-2800 GDD's (crawlers), Base 50F, March 1st Start Date (Source: Cornell Cooperative Extension.)
Host Plant(s) Common Name (Scientific Name): 
Arborvitae (Thuja occidentalis)
Cypress (Cupressus spp.)
Juniper (Juniperus spp.)
Pachysandra (Pachysandra spp.)
Platycladus orientalis
Western red cedar (Thuja plicata)
Yew (Taxus spp.) *Damage caused.
Insect Description: 

The fletcher scale may also be referred to as the arborvitae soft scale and is easily confused with the European fruit lecanium (P. corni); however, the host ranges of the two species differ greatly (the European fruit lecanium is found on a much broader host range). There is one generation of fletcher scales per year. Second instar nymphs (immatures) overwinter. They begin to mature in May and females will lay (500-600; but up to 1000) eggs beneath their bulbous bodies by late May and early June. During this time of development in the spring, plant damage and honeydew may become especially obvious, particularly on yew. Sooty mold may grow on the honeydew. Fully mature females are hemispherical, 3/16th of an inch in length, and light brown. They are found on the twigs of their host. Crawlers may hatch from the eggs by June and crawl short distances to find a suitable location on the host plant to settle and feed. Crawlers are oval, flat, and yellowish in color and typically hatch from their eggs with synchronized timing. They may be found on host plant needles. Nymphs remain on the host plants through the fall and overwinter on the twigs or the needles. 

Damage to Host: 

This insect is typically a more serious pest of Taxus than arborvitae. It may weaken yew, cause foliage to drop, and result in a heavy coating of sooty mold on the foliage and twigs following copious amounts of honeydew production in the spring. Twigs and stems are the primary locations for this insect to be found on yew. In some cases where a heavy infestation is present, small shrubs may be killed. 


Scout for honeydew and sooty mold in the spring when overwintered nymphs are maturing into egg laying females. Look at terminal twigs for the puffed up females from the end of May to June. When populations are low, this insect may be difficult to find so flip twigs over and search multiple branches across multiple plants (if present).

Cultural Management: 

If heavily infested branches are found, given that the crawlers of this insect do not move too far from the dead females and the population may be limited to a small area at first, these branches can be pruned from the host and destroyed prior to egg hatch in June.

Natural Enemies & Biological Control: 

The fletcher scale is native to the United States and has a suite of natural enemies that should be protected by selecting reduced risk management options whenever management is deemed necessary. Natural enemies of the fletcher scale that have been reported include but are not limited to: a species of fungus weevil (Anthribidae: Anthribus nebulosus), parasitic wasps (Aphelinidae; Coccophagus fletcheri and Coccophagus lycimnia & Encyrtidae; Blastothrix spp., Cheiloneurus spp., Encyrtus spp., Metablastothrix spp., and Metaphycus spp.), and green lacewings (Chrysopidae; Pseudomallada prasinus).

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: .