One of the most notorious pests of
hardwood trees in the eastern
Species: Lymantria dispar
History of the Invasion
• Etienne Leopold Trouvelot
(December 26, 1827 – April 22, 1895)
• He fled from France during a
coup d’etat in 1852, and settled in what
is now Medford, Massachusetts
• He made a living as an artist, however
he was also an amateur in entomology
(the study of insects)
• Trouvelot wanted to do something
about the growing taxes on imported
Etienne Leopold Trouvelot
silks from France and Italy since there
was a disease running through their
• Trouvelot went to France in the
1860s and on his return trip, he
brought some gypsy moth egg
masses with him to see if they
could be used for silk
production in America
• While he was culturing the
moths in his backyard, the
larva somehow escaped
• Trouvelot tried to take action
when he discovered that they
were gone by notifying local
Early attempt at gypsy • However, no response took
moth eradication… place
obviously unsuccessful as
have been all other • Trouvelot turned to the field of
methods. astronomy soon after, losing
interest in entomology
Gypsy Moth Life Cycle Stages
Longest stage, typically July through April.
• Eggs laid in large egg masses, containing 500-1000 eggs
• Eggs need to be kept warm and dry, and the female covers
the masses with velvety hairs from their bodies
• Eggs placed in sheltered areas to survive the potentially
harsh overwintering stage
• Caterpillar stage, early spring to mid May.
• Larvae go through 5 to 6 larval stages (instars). Males
have 5 and females 6 due to size. Between stages they
molt by shedding their skin.
High growth period where defoliation occurs
Dark-colored and covered with setae (hair-like
bristles), with five pairs of blue dots followed by six
pairs of red dots lining the back.
Since females are flightless, how do they get around?
• Occurs as soon as the newly hatched larva emerge
because they can be found on the host trees hanging
from a silken thread. Once the wind picks up, it will
carry the larva about a mile in distance (ballooning)
• Occurs when people transport the larva miles from the
infected areas by car, in or on household goods, or on
wood products such as whole tree timber or firewood
• Humans are a major problem in controlling the spread
of the moth.
• If the public becomes more educated, will that stop every
occurrence, or will there still be occasions where the
moth is still dispersed?
• Late June through July, 10-14 days.
• Gypsy moth pupae are covered with brown, tear-drop
shaped protective shells about 1 to 2 inches long.
• Caterpillars seek hidden spots in which to pupate. This is
important because once they have pupated, they are
quite vulnerable to attack by predators and parasites.
• Adult gypsy moths emerge in mid July.
Males are dark brown to grey, are good fliers, and
have feathery antennae.
Females are cream colored, larger and flightless.
Adult stage, contd.
• Adults live for 7-10 days, and do not feed on leaves.
• Newly emerged adult females release a sex pheromone (a
strong scent) that attracts males.
• Males can detect female pheromones from a mile away.
After mating, females begin to lay eggs.
• Females usually deposit their eggs just a few inches from
where they emerged from their pupal stage.
• Egg laying completes the life cycle, and the adults die.
Gypsy moth egg Gypsy moth Older gypsy
masses on the larvae moth larvae
trunk and branch emerging from showing five
of a tree egg mass (first pairs of
instar) raised blue
spots and six
Gypsy moth Male gypsy Female gypsy
pupae after all moths will moth laying
instars are emerge first eggs after
completed mating occurs
European and Asiatic Hybrid
• First identified in North America late in 1991 near the
Port of Vancouver in British Columbia, Canada. Moths
were discovered in Washington, Oregon, and British
Columbia shortly after.
• Ships infested with egg masses from ports in eastern
Russia probably introduced the pest to North America
while visiting ports on the West Coast. Scientists believe
that while the ships were docked, larvae hatched from
the eggs and were blown ashore.
Hybrids may be resistant to particular means of controls.
Feed more readily on conifers
Have better flight capabilities (females capable of flight)
Have a broader host range
Norfolk Island Pine
Asian gypsy moth survey 2005-08
• Gypsy moths are known to feed on more
than 500 species of plants, principally
broad-leafed trees and shrubs. In the
eastern U.S., the gypsy moth’s favorite
trees include apple, speckled alder,
basswood, gray and river birch,
hawthorn, oak (many species but
preferentially white oak), poplar, and
• The gypsy moth tends to avoid ash trees,
tulip trees, American sycamores,
butternut, and black walnut trees
Effects of Defoliation
• Effects depend on many factors, including: time of year,
consecutive defoliations, soil moisture, and sp.
• If less than 50 percent of their crown is defoliated, most
hardwoods will experience only a slight reduction (or
loss) in radial growth
• If more than 50 percent of their crown is defoliated,
most hardwoods will refoliate or produce a second flush
of foliage by midsummer
• Trees weakened by consecutive defoliations are also
vulnerable to attack by disease organisms and other
Rate of Spread
• Maps show that the moth has spread south and west at a
rate of up to 20.9 km/year in some areas
• Gypsy moths have even been found in eastern Canada
• Scientists believe that the gypsy moths arrived in
Michigan and Ontario as a result of an accidental
introduction in the early 1960s (though they are not
really sure) and there were failed attempts to eradicate it
European Gypsy Moth Survey 2005-08
General range of the gypsy moth as of 2003. Photo courtesy of Sandy
• The USDA Forest Service is
currently working on a
national project in order to
slow down the spread of the
• This is based upon the grids
of pheromone traps along
the expanding front in order
to detect isolated colonies
• These colonies are then
eradicated or suppressed in
hopes of preventing them
from coalescing, and this
would decrease the rate of
Why is this a problem?
• Gypsy moths make their homes in many of the
hardwood trees here in the U.S., mainly in oaks
and aspen trees
• Highest concentration of gypsy moth colonies can
be found in the southern Appalachian Mountains,
and within the northern lake states
• Gypsy moth populations can fluctuate within the
forest stand depending on the breakout; densities
could be 1 egg mass per ha to over 1,000 per ha
• Whenever the densities reach over 1,000 per had or
higher trees could become completely defoliated
• Major changes will begin to • Most studies are showing
appear in the vegetation that forest compositional
since the gypsy moths will changes with the gypsy
eat almost anything in moth defoliation indicate
that less susceptible species
(in the near future) will
• One of the biggest and dominate; which in turn
major concerns is that will present the forest with
there will be a potential
loss of the economically problems
critical and ecologically
dominant on the oak
Defoliated ridge-top, western Massachusetts
Cluster of trees killed following gypsy moth defoliation, central PA.
Defoliations like shown can significantly alter the habitat by
removing high canopy species and promoting increases in shrub
species like the Eastern Towhee (Pipilo erythrophthalmus)
• Deer Mice (Peromyscus)
• considered the most important
predator of low-density gypsy
moth populations and their
abundance may be critical in
populations go into an
• abundance is strongly affected
by the amount of mast (e.g.,
acorns) in the previous year Peromyscus maniculatus
Biological Controls, contd.
• Tachnid Flies (family Tachinidae)
• Parasitize gypsy moth
populations. While they may
become quite abundant during a
gypsy moth outbreak, they
apparently have little effect on the
Parasitoid wasps (family
• Parasitize moths as well, but has
little effect on population
• Cuckoos (family Cuculidae) have been
known to prey on caterpillars.
• Chickadees (family Paridae) will peck
at egg masses.
• In general, birds do not have a strong
effect on gypsy moth population
• Viral disease, sometimes also known as
“wilt” is naturally occurring in all gypsy
• It is caused by a nucleopolyhedrosis virus
(NPV), and is derived by the existence of a
matrix of polyhedral proteins that are
surrounded by the viral DNA
• Infection occurs when caterpillars eat
foliage contaminated with this viral
Virus killed gypsy moth larva
• At low populations not much happens,
though when there is a high population
level the virus works more effectively
• Fungal biological control
• Presence of E. maimaiga may
be determined by late instar
gypsy moth larvae which,
when infected with this fungus,
die hanging vertically from
tree trunks with prolegs
extended laterally. The
cadavers subsequently fall to
the bases of trees
• Quite family-specific to gypsy
moth, but highly variable and
unpredictable as a control Gypsy moth remains after E. maimaiga
a synthetic pesticide
• Became available after World War
• Banned in 1972, due to concerns over
environmental contamination, and
its effect on the thinning of avian egg
• Controversial insecticide initially used with DDT.
• Known effects include:
Can wipe out bee colonies.
Causes birth defects in mammals, especially dogs.
Worsens the condition of people with hypertension and people on anti-depressant drugs.
Impairs the function of the pituitary gland, the thyroid gland, and the reproductive system.
Causes hyperactivity and learning disabilities in mammals.
Could increase the chance of heart attack in people with weak hearts.
The main break-down product, nitrosocarbaryl, which is easily created in the human gut, is
a potent cancer-causing agent.
It causes irreversible chromosomal damage to human DNA
• Illegal in some countries, including the U.K.
• Insect growth regulator that
interferes with the synthesis of chitin,
essential to arthropod exoskeletons.
• Toxic to a wide spectrum of
arthropods, and persists for a long
period of time in canopy and leaf
• Still used fairly regularly due to cost
Bt (Bacillus thuringiensis)
• World’s most widely used organic insecticide
• The bacterium produces a crystal protein toxin that kills
the cells lining the insect gut. When ingested, the
bacterial cell wall is digested which releases this toxin.
Since insects have guts that are only one cell layer thick,
this toxin literally "eats" a hole in the gut, causing an
infection in the body cavity (only particular insects
• An article by Broderick 2006 showed that Bt only kills
gypsy moths when other native bacteria are present in
the insect's intestines.
What are local agencies doing to fix
• Many local agencies are working on ways to stop the spread
of the gypsy moth; many states have already lost millions of
acres due to this invader
• States like Pennsylvania and West Virginia are trying to
make the general public aware of the growing problem at
• Many areas that are infected badly are holding work shops
to help educate the public in what to do if they spot the
moths on their trees
• In West Virginia, gypsy moths appeared in 1972,
and has spread across the eastern panhandle and
northern counties of the state
• The local Division of Forestry department has five
essentials steps in which would minimize the impact
that the gypsy moth, and these are:
• Identify stands where the severe impacts are likely
• Determine when defoliating populations are
• Spray to prevent heavy defoliation
• Use silviculture to minimize impacts
• Salvage dead trees within two years
• Gypsy moth regulatory program
• Other states like Wisconsin • Woodlots also need to be
are changing their stocked with trees and
silvicultural techniques to thinned to proper densities
help control the problem in order to control the
• Selection and spacing of the
hardwoods trees could help • The variety of trees that are
reduce the speed in which found within a woodlot
the gypsy moths move could also help slow down
an outbreak by providing
• Also, the type of trees that less suitable hosts for the
are planted could also affect moth
how many will die after a
Management and Research
• Over the past 20 years, • In 1992, the USDA Forest
several millions of acres of Service began a pilot
forest land have been program in order to test the
aerially sprayed with feasibility of slowing the
pesticides to control the spread of the gypsy moth
• There are areas in the • These STS pilot programs
infected areas that are are currently being done in
treated by private North Carolina, Virginia,
companies, or by joint West Virginia, and also in
programs of state Michigan
governments and the
USDA Forest Service
• So far, intensive studies have been done over the 100
years in North America to figure out how to either
control or stop this growing problem
All work is being funded by the USDA Forest Service,
the USDA Agricultural Research Service, the USDA
Cooperative State Research Service, the USDA Animal
and Plant Health and Inspection Service and
state and private universities