Insect and Disease Fact Sheet Compliments of New Century



Lecanium Scales


Hosts: Numerous shade trees and woody ornamentals


Lecanium Scale with honeydew on branch.

Lecanium Scale encrustation on branch.


Description: Lecanium scale is a term used to refer to any of a dozen species of soft scales associated with shade trees and woody ornamentals. Due to similarities between the different lecanium species, even scale experts are unable to consistently provide precise identifications of submitted specimens. However, because most lecanium scales have similar life histories, accurate identifications may only be of academic importance.


Lecanium scales over winter as 2nd instar nymphs on the twigs and branches of infested trees. During spring, nymphs resume feeding. By late spring and early summer, female scales produce (with or without the presence of males) and deposit their eggs. Females then die, but remain in place, with the eggs protected beneath their bodies.

During the summer, scale crawlers emerge from eggs and crawl to the leaves where they feed for the duration of the summer. In the fall, lecanium scales migrate back to adjacent twigs and branches where they over winter. Lecanium scales produce a single generation per year.

Lecanium Scale on oak tree. Note the “blackening” of the branches.


Although female Lecanium scales can individually produce more than 3,000 eggs each, their populations generally are kept "in check" by populations of naturally occurring predators and parasites. However, any disruption of beneficial populations can result in rapid Lecanium scale population buildups over a several year period. The feeding of many developing scales during their rapid growth period in the spring results in heavy "raining" of honeydew onto whatever is parked/positioned beneath heavily infested trees. A black sooty mold growing on the honeydew-ladened branches results in an unacceptable blackened appearance to the tree. Branch dieback is also consequences of massive Lecanium scale populations.



Recommendations:  As mentioned, populations of naturally occurring predators and parasites normally keep Lecanium scale populations "in check." Unfortunately, populations of beneficials are greatly reduced or eliminated in neighborhoods which receive massive annual insecticide applications.  In these instances, previously non-problematic insects (such as Lecanium scales) may emerge as a primary pest with few natural enemies to control it.


If Lecanium scale populations require chemical control, it is essential to direct treatments towards the susceptible stage: THE CRAWLERS WHICH EMERGE FROM UNDER THE PROTECTION OF THE "DEAD" MOTHER'S BODY! The timing of this event cannot be based on a calendar date. Rather, the presence of crawlers must be determined on visual observations of the presence of this life stage as they migrate to foliage during the summer.


Various insecticides are registered for use against scale crawlers. Tree service personnel are aware of such listed products. The preferred insecticide of choice may vary between businesses, their final choice resting on their experience of product effectiveness.


Information obtained through Kansas State University


Insect and Disease Fact Sheet Compliments of New Century