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LECANIUM SCALES

James R. Baker, Extension Entomologist

CAUTION: This information was developed for North Carolina and may not apply to other areas.


European fruit lecanium, Parthenolecanium corni (Bouche); European peach scale, Parthenolecanium persicae (Fabricius); Fletcher scale, Parthenolecanium fletcheri (Cockerell); oak lecanium scale, Parthenolecanium quercifex (Fitch); Coccidae; HEMIPTERA

encrusted twig scale imageFemale lecanium scales are 2 to 6 mm in diameter. When fully grown, female scales are rounded, reddish to dark brown and sometimes have a pale waxy bloom. Male scales are flying insects (each wing is about 2 mm long) which are brown. Males have a long "tail" called the style, and they have two white hairs that trail from the body. Eggs are almost white and are 0.25 to 0.35 mm long. The eggs resemble fine pollen. New nymphs are called crawlers. Crawlers are flat, pale insects with conspicuous legs and antennae. Older nymphs are flat and brown. The legs and antennae become less noticeable as they mature. Males develop into a pupal stage that is a pale peach color and is covered by a translucent waxy coat.
 

BIOLOGY

Lecanium scales are found throughout North America, and many kinds of trees can be infested with lecanium scales, but dogwoods and oaks are the most frequently reported hosts. Lecanium scales suck sap from the leaves and twigs of trees. They excrete honeydew, Severe infestations may stunt plant development and cause premature leaf drop and small flowers. Sooty molds may also develop on the honeydew.

 Lecanium scales lay 1,000 to 5,000 eggs each in April and May. These hatch and crawlers move to the leaves where they feed until late summer. The nymphs molt into the second instar which moves

drawing of life stages of oak lecanium scale

back to the twigs to spend the winter. They hibernate under a thin, waxy shield. Males usually pupate and emerge in early spring. Some lecanium scales can lay fertile eggs without mating. As adult females mature, they become rounded and hardened. As the eggs are laid, the body of the scale shrinks against the outer skin to form a protective shield over the eggs.

CONTROL

Optimizing tree growing conditions is always best.  Perform a soil test, irrigate during drought, avoid soil compaction beneath trees, remove turf from beneath trees to avoid competition and excessive fertilization.  Apply pesticide sprays only if necessary and only to the crawlers. These scales are not easily eradicated. The scales on the twigs are protected from pesticides by the thin waxy covering or the adult scales are less susceptible to pesticides. However, the crawlers are unprotected. By mid-June, most of the eggs should have hatched and most of the crawlers should be on the leaves. The following pesticides are labeled for scales or scale crawlers and can be used for Lecanium scale control:
 
 
Pesticide (Trade Name) Formulation
*acephate  (Orthenex)  
acephate  (Orthene) 75% soluble powder
bifenthrin (Talstar) 10% wettable powder
*carbaryl  (Sevin) 50% wettable powder
*carbaryl  (Sevin) 80% soluble powder
cyfluthrin  (Decathlon) 20% wettable powder
dinotefuran (Safari) systemic; may be appropriate in some settings
fenoxycarb (Precision) 25% water soluble packets
*malathion
*malathion 
57% emulsifiable conc.
25% wettable powder
*fluvalinate  (Mavrik) 23% flowable concentrate
*horticultural oil alone or + malathion 
hort oil alone provides the fewest off-target effects

* Suitable for home use. There may be additional chemicals available.

Other Resources

For assistance with a specific problem, contact your local North Carolina Cooperative Extension Service personnel.


Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
© 2001 NC Cooperative Extension Service
Prepared by: James R. Baker Extension Entomologist

ENT/ort-36 April 1994 (Revised)
Web page last reviewed January, 2011 by the webperson.