Lecanium scales are common insect pests that infest a wide range of species.  There are approximately one dozen different species of these soft scales that are difficult to distinguish from one another visually.  Fortunately, life history and management of these species are quite similar to each other.  Lecanium scales suck sap out of the leaves and twigs, and the honeydew they excrete often becomes covered with sooty mold. 

Lecanium scales overwinter on twigs and branches in an immature/nymphal stage.  In the spring they continue development, and mature females produce large numbers of eggs.  Crawlers emerge in late spring/early summer and migrate to the undersides of leaves where they feed until late summer.  At this time they move back to the twigs where they overwinter.  There is one generation per year.

Lecanium scales can cause twig dieback, stunted plant development, and premature leaf drop.  The presence of sooty mold on the excreted honeydew may also give a blackened appearance to foliage and branches in severe cases.  Ants, bees, and wasps may be attracted to the honeydew, and could be a cue to look for lecanium scales.

Susceptible Hosts
Lecanium scales may be found on a wide range of trees including, but not limited to, oaks, maples, linden, and birch.  Different species of lecanium scales show preference for different host species.  A few examples include:
* Fletcher scale – arborvitae and yew
* Terrapin scale – maples and peach
* Hickory lecanium scale – hickory and elm
* Globose scale – stone fruits

Pest Names
* Hickory lecanium scale – Eulecanium caryae
* European fruit lecanium – Parthenolecanium corni
* Oak lecanium - Parthenolecanium quercifex
* Terrapin scale – Mesolecanium nigrofasciatum
* European peach scale – Parthenolecanium persicae

Symptoms
* Heavily infested trees may display dieback of branches and twigs
* Premature leaf drop may occur in late summer
* During severe stress, a heavy infestation of lecanium scales could kill an entire tree
* Heaviest damage occurs in spring and early summer
* Honeydew is excreted on twigs, branches, and leaves

Signs
Adults
* Adult females have a hemispherical body that is approximately 0.4 inches in diameter.
* Brown in color, often with a shiny outer surface.
* Most frequently seen adhered to small twigs – may be found there in abundance

Crawlers
* May be found migrating to undersides of leaves in early summer

Life Cycle
* Thousands of eggs are laid in early spring (April and May).
* Eggs hatch and crawlers move to the leave to feed until late summer.
* Second instars move back to the twigs to overwinter under a thin, waxy shield.

Distinguishing from Look-alikes
* Aphids and other sucking insects may excrete honeydew that attracts other insects and sooty mold.  Do not assume that the presence of these secondary infestations results only from scales.
* Lecanium scales include a number of different species that are very difficult to distinguish from each other even for highly trained entomologists.
* Differentiating soft scales (Lecanium) from hard scales is important because their management strategies differ.
* Hard/armored scales have a flattened, platelike cover that is less than 1/8 of an inch in diameter.  The cover often has a slightly different colored protuberance.  Concentric rings form as each nymphal stage secretes an enlargement to the cover.  The actual insect body is under the cover.
* The cover of lecanium scales is part of the insect body, and cannot be removed.
* Armored scales do not excrete honeydew, whereas soft/lecanium scales do.

Monitor host plants for the presence of adults, crawlers, and honeydew during the season. 

Xytect and Transtect soil applications must be timed to ensure high titer levels are within the tree at the time of the first generation crawler hatch and feeding.  

When infestation reaches an undesirable level the primary goal is to control the crawler stage of the insect’s life cycle using foliar sprays.  Crawlers are most active in the early summer, and are very susceptible to insecticide control.  Once settled on leaves or twigs, they secrete a waxy covering that provides protection, so timing of sprays is important. 

Expectations:

* Xytect and Transtect will provide a high level of control of all soft scales.  Arborists should use foliar sprays for immediate activity against crawlers or for management of overwintering females on twigs with dormant sprays.  Properly timed soil applications of Xytect or Transtect will work extremely well for most soft scales.

* Females grow rapidly in spring and produce 1,000 to 5,000 eggs. Eggs hatch in April and May and crawlers migrate to the leaves where they feed until late summer.  The nymphs molt and overwinter as second instars on dormant twigs making dormant oil applications a good option, especially if soil applications of Xytect or Transtect have not been previously applied.

Other Treatment Practices:
* If trees display dieback, premature leaf drop, or other stress associated with lecanium scales, then measures should be taken to improve tree health.  These can include root invigoration practices with an air tool, mulch, prescription based fertilization and regular irrigation during dry periods

* Heavily infested twigs may be pruned off the tree to reduce the insect pressure.

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