|
For information or questions about biological control contact
Nancy Webber:
nancy@fcwp.org 332-1052
Lars Baker
larsbaker@wyoming.com
332-1052
Since 1978 Fremont County Weed & Pest has
been actively involved with research on the biological
control of weeds by insects. These biological control agents
have been screened in Europe and Asia where our weeds are
native, for release in North America. Only insects that are
proven to be host-specific are considered to provide safety
for related native plants and economic agricultural crops.
Fremont County Weed & Pest was the first in Wyoming to
dedicate a staff position to Bio-Control work. In 1999 this
position was made a full year benefited position.
In Fremont County we have released 28 species of bio-control
agents on 10 weed species.
Leafy Spurge – Most of the focus of the biological control
program in Fremont County has been on leafy spurge. We have
been releasing bio-agents on this weed since the late1980’s.
Seven species of insects have been released on leafy spurge.
The most successful of these have been the Aphthona beetles,
A.
nigriscutis and
A. lasertosa. By feeding on the tops of
the plants during the growing season and the root hairs
throughout the winter the beetles have been very effective in
greatly reducing the density and vigor of spurge over
hundreds of acres in Fremont County. Millions of these flea
beetles have been collected and redistributed over the past
15 years. Two other species of Aphthona beetles have been
released in the Lander area, both
A. flava and
A. cyparissiae have been released and become established but
have not had dramatic effects on leafy spurge.
The leafy
spurge hawk moth,
Hyles euphorbiae, is a strong flyer and
can be found across the county, but being just a defoliator
it has little effect on the spurge plants.
A stem borer,
Obera erythrocephala, was first released in 1980 then again
in 1996 but was not recovered until 2002. It is now well
established in the river bottom between Lander and Hudson
and will have a negative effect on the spurge as the
population grows in these areas.
Another introduced insect
doing well in the river bottoms is the leafy spurge tip gall
midge,
Spurgia esulae, which galls the growing tips of the
plants, prevents flowering, and stunts the plants. In
Fremont County we have been collecting and redistributing
Spurgia galls since 1996.
Download
this poster (a Microsoft publisher file) on the subject of
Monitoring of Ground Cover Post Release of
Aphthona nigriscutis
for the Control of Leafy spurge
Download
this poster (a Microsoft publisher file) on the subject of
Aphthona nigriscutis,
a Biological Control Agent for
Euphorbia esula
(Leafy Spurge) on a Native Plant
Euphorbia robusta
These are before and after photographs
of biological control:
1991
1998
Canada Thistle – This weed is naturalized throughout the
county, almost anywhere there is water Canada thistle can be
found. Since the early 1990’s we have been using bio-control
agents to try to control the vigor and spread of this tough
perennial weed. Four insects have been released on Canada
thistle; the Canada thistle stem weevil,
Ceutrohynchus
litura, the Canada thistle stem gall fly,
Urophora cardui,
Cassida rubiginosa, a defoliating beetle, and the Canada
thistle bud weevil,
Larinus planus. All of these agents have
become established and are having some effect on Canada
thistle.
Urophora cardui populations have expanded to the
point where the stem galls are collected for redistribution
in the fall.
Ceutrohynchus litura seems to be having the
greatest impact in areas with saturated soils where it has
been released. It is a difficult insect to collect and it is
more cost effective for us to purchase this insect to
establish new populations.
Musk Thistle – The bio-control program for this biannual
weed has been very successful. Two bio-agents were released
in Fremont County in the late 1980’s, a seed head weevil,
Rhinocyllus conicus, and a crown weevil,
Trichosirocalus
horridus. When these agents were released musk thistle had a
substantial impact with over 11,000 acres in the County. The
insects have had a tremendous impact on the population of
musk thistle. There is now only about 1000 acres of this
weed scattered across the county; none on which is
economically important. All the musk thistle found in
Fremont County is infested with both of these insects.
Scotch Thistle – There have been no bio-control agents
introduced specifically for this weed. There are a few
limited infestations of scotch thistle in Fremont County.
Plumeless Thistle – Fremont County does not have this
noxious weed. Insect biological agents introduced to control
musk thistle,
Rhinocyllus conicus and
Trichosirocalus
horridus, also attack plumeless thistle.
Dalmatian Toadflax – There is still relatively little of
this weed in the county. What we have is found
primarily in the Lander area having escaped from ornamental
plantings, however, we are
increasingly seeing toadflax along roadsides and rangeland. There
have been three bio-control agents released on Dalmatian
toadflax in Fremont County. The toadflax flower-feeding
beetle,
Brachypterolus pulicarius, and the toadflax moth,
Calophasia lunula, were introduced in the mid 1990’s and the
toadflax stem weevil,
Mecinus janthinus, was introduced in
2003. Both the flower-feeding beetle and the stem weevil
have become well established and we are able to collect and
redistribute the weevil to other sites. The toadflax moth
has never been recovered.
Yellow Toadflax – With only a few, very small infestations
of this weed in Fremont County we are working on the
eradication of yellow toadflax. An introduced weevil,
Gymnetron antirrhini, that causes a decline in seed
production is wide spread across the state and infests the
yellow toadflax found in Fremont County.
Spotted Knapweed – This weed has been present in Fremont
County for over 50 years, but the infestations are still
very limited. While the Weed & Pest crews treat this plant
very aggressively, we have introduced six species of insects
on spotted knapweed in an effort to catch the plants that
are missed. The bio-control agents released in the mid
1990’s included: the spotted knapweed seed head moth,
Metzeneria paucipunctel, the lesser knapweed flower weevil,
Larinus minutus, the green clearwing fly,
Terellia viren,
the banded gall fly,
Urophora affinis, and the UV knapweed
seed head fly,
Urophora quadrifasciata.
Larinus minutus
is well
established south of Lander with populations high enough for
limited collection and redistribution. In 2005 a large
infestation of spotted knapweed was discovered in a remote,
rough area of the Wind River Indian Reservation that had
been burned in 2000. Large releases of
Larinus minutus and
the knapweed root weevil,
Cyphocleonus achates, were made in
the area. We expect to be able to recover this agent in
2006.
Diffuse Knapweed – There is very little diffuse knapweed in
Fremont County and, as far as we know, it is in a limited
area. Four bio-control agents have been released on a mixed
infestation of spotted and diffuse knapweed in the Green
Mountain area in southwestern Fremont County. In 1995 the
insects released included: the lesser knapweed flower
weevil,
Larinus minutus, the green clearwing fly,
Terellia
viren, and the banded gall fly,
urophora affinis. In 1996 an
additional mixed release of
urophora affinis and
Urophora
quadrifasciata was made. None of these agents have been
recovered from the Green Mountain site.
Russian Knapweed – This noxious weed dominates many acres in
Fremont County. The Russian knapweed gall nematode,
Subanguina picridis,
has been the only bio-agent available for Russian knapweed.
This agent has been well established since its release in
the mid 1990’s. It is galling the knapweed plants at the
release sites, but does not move
on its own. Fremont County Weed & Pest is helping to fund
research taking place in Europe to find and test highly
selective insect agents of Russian knapweed for introduction
into North America. We hope to have two new bio-agents
approved for introduction soon.
Field Bindweed – This weed
is widespread across much of Fremont County, causing
problems in agricultural settings, along roadsides,
in lawn and garden areas and industrial
sites. Two bio-control agents are being used in the County
to suppress this weed. The Bindweed gall mite,
Aceria
malherbae, was first released in 1998 in the Ethete area of
the Wind River Indian Reservation. We recovered and were
able to move infested plant material for redistribution in
2003. Since then the field bindweed at the release site has
been eliminated by this agent. In addition to material
collected locally we have received mite infected material
from Colorado through APHIS. We have had limited success in
getting new bio-sites established with this agent. In 2004
we released both adult and larva of the bindweed moth,
Tyta
luctuosa, also received from APHIS. We will be surveying for
the moth this summer to determine establishment.
Hoary Cress – There are no bio-control agents available for
this abundant weed yet. Research is taking place in Europe to find
and test highly selective insect agents for introduction
onto Hoary Cress in North America.
Perennial Pepperweed - There are no bio-control agents
available for this weed yet. Fremont County Weed & Pest is
helping fund research taking place in Europe to find and
test insect agents of Perennial Pepperweed for introduction
into North America.
Saltcedar – With extensive infestations of this shrub on our
major drainages Fremont County has been very involved in the
effort to get bio-agents for saltcedar. The Saltcedar leaf
beetle,
Diorhabda elongata was released at two research
sites in the Boysen reservoir area during the summer of
2005. We are expecting that this defoliating agent will successfully
establish and spread as it has in
other areas of the mountain west. Within the next few years
we hope to be able to collect and redistribute Diorhabda in
Fremont County.
Houndstongue - There are no bio-control agents available in
the United States for this weed yet. Fremont County Weed &
Pest is helping fund research taking place in Europe to find
and test highly selective insect agents of houndstongue for
introduction into North America.
Dyers Woad – A small stand
of this weed was discovered in the Lander area in 2004.
There are no bio-control agents available for this weed yet.
Purple Loosestrife – This weed has only been found in garden
plantings in Fremont County. These plantings have been
eradicated. There are a number of beetle species that are
effective bio-control agents on this weed.
Puncturevine – In 1983 the Puncture vine seed weevil,
Microlarinus lareynii, was released on puncture vine in the
town of Shoshoni, though we have seen no evidence of
establishment.
Skeletonleaf Bursage – This weed can be found in a few areas
of Fremont County, but is not of great concern. There are no
bio-control agents available for the weed.
Quackgrass – This weed is wide spread across Fremont County,
having been planted as a forage crop. There are no
bio-control agents available for this weed.
Perennial Sowthistle – This weed is present in Fremont
County but is not considered a big problem. There are no
bio-control agents available for this weed.
Oxeye Daisy – There is one extensive infestation of Oxeye
Daisy in a back country area in northwest Fremont County
which is being aggressively treated. Unfortunately there are
no bio-agents available for this weed.
Common Burdock – There are no bio-control agents available
for this weed. Common burdock is not a problem weed in
Fremont County.
 |
