Insect
and Disease Fact Sheet Compliments of New Century
1-877-79TREES
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
1-877-79TREES