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Gypsy Moths (PowerPoint)

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					       Gypsy Moths
One of the most notorious pests of
hardwood trees in the eastern
United States
    Scientific Classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Lymantriidae
Tribe: Lymantrini
Genus: Lymantria
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
  silkworm populations
                            • 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
                              entomologists
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
                      Egg Stage
  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
                  Larvae 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?
              Natural Dispersal
• 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)
             Artificial Dispersal
• 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?
                   Pupae Stage
• 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 Stage
• 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
                                     pairs of
                                     raised brick-
                                     red spots
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.
               Hybrid, contd.
    Hybrids may be resistant to particular means of controls.
  They also:
  Feed more readily on conifers
  Have better flight capabilities (females capable of flight)
    Have a broader host range




                                            Norfolk Island Pine

                                           Araucaria heterophylla
Asian gypsy moth survey 2005-08




     http://pest.ceris.purdue.edu/searchmap.php?selectName=ITAXQBA
                                  Hosts
• 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
  willow
• The gypsy moth tends to avoid ash trees,
  tulip trees, American sycamores,
  butternut, and black walnut trees



                                             White Oak
                                             Quercus alba
           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
  insects
                 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
  and Michigan

• 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
  there
European Gypsy Moth Survey 2005-08




       http://pest.ceris.purdue.edu/searchmap.php?selectName=ITAXAIA
General range of the gypsy moth as of 2003. Photo courtesy of Sandy
Liebhold.
• The USDA Forest Service is
  currently working on a
  national project in order to
  slow down the spread of the
  gypsy moths
• 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
  spread
         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
                  Forest Effects?
• 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
  sight
                                  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
  species
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)
               Biological Controls
• Deer Mice (Peromyscus)

• considered the most important
  predator of low-density gypsy
  moth populations and their
  abundance may be critical in
  determining whether
  populations go into an
  outbreak mode

• 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
  population dynamics

  Parasitoid wasps (family
  Braconidae)
• Parasitize moths as well, but has
  little effect on population
  dynamics.
                  Avian Predators

• Cuckoos (family Cuculidae) have been
  known to prey on caterpillars.


                                           Coccyzus americanus
• Chickadees (family Paridae) will peck
  at egg masses.

• In general, birds do not have a strong
  effect on gypsy moth population
  dynamics.

                                            Poecile atricapillus
          Nucleopolyhedrosis Virus
                (Gypcheck)
• Viral disease, sometimes also known as
  “wilt” is naturally occurring in all gypsy
  moth populations
• 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
  oclusion bodies
                                                Virus killed gypsy moth larva
• At low populations not much happens,
  though when there is a high population
  level the virus works more effectively
           Entomophaga maimaiga
• Fungal biological control
  (family Entomophthorales)
• 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
Insecticides
                             DDT
• Dichloro-Diphenyl-Trichloroethane,
  a synthetic pesticide



• Became available after World War
  II



• Banned in 1972, due to concerns over
  environmental contamination, and
  its effect on the thinning of avian egg
  shells
                       Sevin (Carbaryl)
• 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.
                             Dimlin
• 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
  litter.

• Still used fairly regularly due to cost
  and results.
       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
  affected).
• 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
             this problem?
• 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
  hand

• 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
       present
     • 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
                                    spread
• 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
  breakout
        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
  outbreaks

• 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
                      Funding
• 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

				
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