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BEN # 186

Adolf Ceska aceska at CUE.BC.CA
Tue Mar 10 03:52:37 EST 1998


                                                   
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No. 186                              March 10, 1998

aceska at victoria.tc.ca                Victoria, B.C.
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 Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2
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GYPSY MOTH FUNGUS - ENTOMOPHAGA MAIMAIGA

[This article was compiled from published and unpublished papers
that Dr. Ann E. Hajek (Cornell University) kindly sent to me for
use in BEN. - Adolf Ceska]

The gypsy moth, Lymantria dispar (L.), is a  serious  defoliator
of  broadleaved forests in eastern North America. The gypsy moth
is indigenous to  temperate  Eurasia  and  was  introduced  into
Boston  area of Massachusetts in 1869. In eastern North America,
populations of  this  insect  pest  undergo  periodic  outbreaks
increasing  to high densities that result in widespread defolia-
tion to an average 2.0 million forested hectares  per  year.  In
British Columbia we experienced periodic gypsy moth infestations
on  Saltspring  Island,  around  Victoria  and Vancouver, and in
Kelowna.

In eastern North America, the gypsy moth is subject to a variety
of naturally occurring infectious  diseases  caused  by  several
kinds  of bacteria, fungi, and a nucleopolyhedrosis virus (NPV),
which was  inadvertently  introduced  with  gypsy  moth  or  its
parasites.  There  are  six species of entomopathogenic (causing
disease in insects) fungi known to infect the gypsy moth.

The fungal class Zygomycetes, which includes the bread molds, is
a primitive group of fungi  with  no  species  native  to  North
America  known  to  infect gypsy moth. Species in one zygomycete
order, the Entomophthorales, are predominantly insect pathogens.
Many entomophthoralean pathogens are  known  to  cause  dramatic
epizootics (disease outbreaks) in insect populations.

In 1984, researchers isolated this entomophthoralean fungus from
the Asian gypsy moth in Japan and brought isolates to the United
States. Stages of this fungus now could be maintained year round
in  the laboratory using several different culture media, rather
than having to be perpetuated on gypsy  moth  larvae.  The  name
Entomophaga  maimaiga was given to the Japanese isolates of this
fungus. The specific name for this new species, "maimaiga,"  was
based on the Japanese common name for the gypsy moth. Host range
studies have shown that E. maimaiga does not infect insect other
than Lepidoptera.

Laboratory  bioassays  were conducted over two years to maximize
the diversity of species  that  were  tested.  These  laboratory
tests  optimized  chances  for  E. maimaiga to cause infections,
yielding information about an  idealized  host  range  for  this
pathogen.  Out of a total of 78 species tested from 10 different
superfamilies, cadavers of 35.6 percent of the species  produced
E.  maimaiga  spores.  Infections occurred in 7 of the 10 super-
families tested although infection levels were 50 percent within
both  the  Bombycoidea  (Malacosoma  disstria)  and  Sphingoidea
(Manduca  sexta).  In  the Noctuoidea, >50 percent infection was
only found within the Lymantriidae.

However, laboratory bioassays optimize chances for infection and
frequently do not  agree  with  field  observations.  Therefore,
during 1995, Linda Butler, Dick Reardon, and Ann Hajek continued
their  studies  by  investigating  the host range of E. maimaiga
under field conditions. With the help  of  Steve  Talley  (Rock-
bridge  County, Virginia), they sampled larvae of gypsy moth and
non-target Lepidoptera in  seven  plots  in  Virginia  where  E.
maimaiga was present and active. The moderate density gypsy moth
populations  in  these  plots  experienced  40.8  - 97.5 percent
infection by E. maimaiga during the field season.

A total of 1421 larvae from 53 species belonging to  7  lepidop-
teran families and 4 subfamilies were collected and reared. Only
two  individuals,  one  of 296 Malacosoma disstria (Bombycoidea:
Lasiocampidae) and one of  96  Catocala  ilia  (Noctuodea:  Noc-
tuidae)  became  infected by E. maimaiga. (Unfortunately C. ilia
had not been tested during laboratory  bioassays.)  In  summary,
laboratory  studies demonstrated infection by E. maimaiga over a
greater diversity of species compared with  field  studies,  and
for those species infected in both the laboratory and field, the
percent  of  infection  was  much higher in the lab studies than
findings from the field.

There is general consensus among scientists  and  pest  managers
that  E.  maimaiga  is  probably  responsible for the decline in
gypsy moth  outbreaks  and  damage  over  the  last  few  years.
However,  we  do  not know if this level of fungus activity will
continue because E. maimaiga has been highly variable and unpre-
dictable. This poses a dilemma for pest managers because  treat-
ment projects must be planned and carried forward well before it
is  known  how  active the fungus might be during the next gypsy
moth season. Consequently, the use of environmentally  safe  and
effective  insecticides  will  continue to be important tools to
reduce damage caused by gypsy moth outbreaks.

Entomophaga maimaiga is effective in both high- and  low-density
gypsy  moth  populations,  unlike  the nucleopolyhedrosis virus,
which is only effective at high-density  moth  populations.  The
fungus  could  play a significant role in the natural control of
gypsy moth, especially in years with a  wet  spring.  Only  time
will  tell  whether  increasing  the  area  where E. maimaiga is
established will lead to constant lower populations of the gypsy
moth in North America.

Acknowledgements. I would like to thank Dr. Ann Hajek for  send-
ing  me  her  published  and  unpublished  papers on Entomophaga
maimaiga and for her permission to use them in BEN. Some  infor-
mation  used  in this article was previously posted in the Gypsy
Moth News that can be reached on the following web site:

   http://www.fsl.wvnet.edu/NA_online/gm_news39/gmnews.html

Further reading:

Reardon, R. & A. Hajek.  1993.  Entomophaga  maimaiga  in  North
   America:  a  review.  Publication  NA-TP-15-93,  USDA  Forest
   Service Northeastern Area, Morgantown, WV. 22 p.
Fungal class Zygomycetes on Dr. Bryce Kendrick's web page:
   http://www.pacificcoast.net/~mycolog/chap3b.htm


SPECIES IDENTIFICATION WEB SITES
From: Vic Rudis <vrudis at usfs.msstate.edu> originally posted
          on FOREST <FOREST at LISTSERV.FUNET.FI>

There are several on line guides to species identification. Here
are several that should be of interest, especially for those  in
North America:

   http://www.colby.edu/info.tech/BI211/PlantFamilyID.html
   http://www.isc.tamu.edu/FLORA/gallery.htm
   http://bluehen.ags.udel.edu/udgarden.html
   http://plants.usda.gov/plants/photogal.cgi
   http://www.wisc.edu/botany/virtual.html
   http://plants.usda.gov/plants/
   http://www.mip.berkeley.edu/bonap/bonap_state_dist_ref.html


GRASS GENERA AND FAMILIES OF FLOWERING PLANTS - KEYS ON WEB
From: Les Watson <lesw at albanyis.com.au> originally posted on
              TAXACOM <taxacom at cmsa.berkeley.edu>

New  HTML and Intkey versions of `Grass Genera of the World' and
`Families of Flowering Plants' were posted recently, at

   http://biodiversity.bio.uno.edu/delta/

Both have been edited and improved in various ways, and for  the
first  time,  they incorporate extensive character illustrations
for use with Intkey. The `Families' character illustrations have
been adapted from the  range  of  taxon  images  presented  with
earlier  versions,  but  the  Poaceae  package now includes (for
example)  numerous  character  and  taxon  photomicrographs  il-
lustrating  leaf  blade  anatomy  and  spikelet details, many of
which which have never been published before.

The Intkey versions are freely available  for  downloading,  but
can  be run directly from the Web using the Windows95/NT version
of the program.


KEYS ON-LINE: LICHEN GENUS PARMELIA OF THE BRITISH ISLES
From: Jeremy Gray <jmgray at argonet.co.uk> Originally posted on
         lichen-l discussion list

A modest contribution but there is a key  to  the  Parmelias  of
Great  Britain  and  Ireland on the British Lichen Society's web
site at

   http://www.argonet.co.uk/users/jmgray/cd/key.htm


WILDFLOWER ILLUSTRATIONS
From: Mary Barkworth <stipoid at cc.usu.edu>

Karl Urban of Umatilla National Forest has developed a series of
line drawings designed for children to color.  They  are  avail-
able, copyright free, from

   http://www.fs.fed.us./r6/uma/flowers.htm

The print version will look much better than the drawing on your
monitor.

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