[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
BEN # 186
BBBBB EEEEEE NN N ISSN 1188-603X
BB B EE NNN N
BBBBB EEEEE NN N N BOTANICAL
BB B EE NN NN ELECTRONIC
BBBBB EEEEEE NN N NEWS
No. 186 March 10, 1998
aceska@victoria.tc.ca Victoria, B.C.
-----------------------------------------------------------
Dr. A. Ceska, P.O.Box 8546, Victoria, B.C. Canada V8W 3S2
-----------------------------------------------------------
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[This article was compiled from published and unpublished papers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@usfs.msstate.edu> originally posted
on FOREST <FOREST@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@albanyis.com.au> originally posted on
TAXACOM <taxacom@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@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@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.
----------------------------------------------------------------
Submissions, subscriptions, etc.: aceska@victoria.tc.ca
BEN is archived at http://www.ou.edu/cas/botany-micro/ben/
________________________________________________________________