Unwelcome Guests
All too frequently, it seems that insects threaten
the beauty, health and occasionally the future of
our trees. Few who experienced the devastating effects
of gypsy moth will forget the sight of barren tree
canopies in May. More recently, those with hemlocks
are likely familiar with the troubling hemlock woolly
adelgid. Unfortunately, as we forecasted last year,
another insect threatens to be a major pest to deciduous
trees.
Winter moth (Operophtera brumata) is a newly introduced
pest in Massachusetts. It is believed that Plymouth
County was the initial site invaded in the Eastern
U.S, possibly as long as seven years ago. Populations
have been continually increasing and effected areas
have expanded rapidly. Winter moth feed on a wide range
of deciduous hosts including apple, crabapple, cherry,
maple, oak, and blueberry.
Dr. Joseph Elkinton, a research forest entomologist
at the University of Massachusetts, is studying the
winter moth, yielding some astonishing results. Dr.
Elkinton estimates that infested areas average 2000-3000
females per tree, each producing up to 150 eggs. This
translates into approximately a quarter million or
more eggs, per tree, that are waiting to hatch in early
spring! Obviously, with such astronomical numbers,
this insect has the ability to spread quickly, infesting
previously unaffected areas.
Last November through December, many were surprised
to see multitudes of brown moths flying at night during
the mild weather. This was the adult male stage of
the winter moth. After
eggs hatch in early spring, the larvae (caterpillars
resembling green inchworms) tunnel into and forage
inside buds before bud break occurs. Delayed bud opening
due to cool weather conditions can lead to increased
damage. Research has shown that just 4 consecutive
years of partial defoliation can lead to branch mortality,
while complete defoliation leads to tree mortality.
While the potential for overwhelming damage is formidable,
winter moth can be effectively controlled. Preventative
treatments require precise timing, beginning in early
spring before leaf and flower buds open.
Consulting with the nation’s leading entomologists
keeps us abreast of the latest innovations in tree
care. We will be using bio-rational materials to control
winter moth. We have found this new class of insect
control products to provide superior pest control with
minimum disruption of beneficial insects and other
nontarget organisms.
Tree protection recommendations were sent to clients
in areas where we expect high winter moth activity.
If you have seen evidence of this insect (past defoliation,
green inchworms, or moth flight in December), please
contact your arborist to discuss strategies to protect
your key landscape trees.
