– The invasive New Zealand mud snail that has been a problem in western U.S.
streams has been detected in Black Earth Creek, a renowned trout stream in Dane
discovery, the first in an inland Midwestern stream, is spurring the state to begin
rapid response procedures to try to contain the snail, and to call on waterfowl
hunters, trappers anglers and hikers to take precautions to avoid accidentally
spreading the species.
is a significant and disappointing find in Wisconsin,” says Bob Wakeman, who
coordinates the Department of Natural Resources aquatic invasive species
efforts. “The New Zealand mud snail can be extremely prolific, has altered the
food chain and may be having an impact on fish populations in Western streams.”
don’t know what the impact will be in Wisconsin, but we do know that there is
no good way to eradicate the snails so we are focusing on containing them as
quickly as we can and ask for citizens’ help in doing that as well.”
says DNR has notified partners of the discovery, and will work with citizens,
the River Alliance of Wisconsin, Trout Unlimited, University of
Wisconsin-Extension, Wisconsin Sea Grant and Dane County to contain the species
through increasing awareness of prevention steps among those who might
inadvertently help spread the snail: hunters, anglers, trappers and hikers.
and wash stations along the area where the invasive species has been detected
are among the educational efforts likely to be used, Wakeman says.
department’s discovery of the snail during routine monitoring for aquatic
invasive species was confirmed earlier this month by Dr. Kathryn Perez from
University of Wisconsin-La Crosse, who identified all individuals in the
samples as belonging to the “Clone 1” population, previously found only in the
western states as far east as Colorado. A “Clone 2” population also exist in
the Great Lakes, which arrived by ballast water.
The New Zealand mud snail, the size of a grain of
sand, has a black and brown shell and is capable of reaching high densities –
up to 500,000 per square meter. The snails outcompete native insects that are
food for fish and other aquatic life but are not good food sources themselves.
snails are listed as a prohibited species in Wisconsin, meaning it’s illegal to
buy, sell, possess or transfer them without a permit.
trout season on the creek has closed for winter, hunters, hikers and trappers
visiting the Driftless area should take care to review gear disinfection
protocols – particularly for waders, where the tiny snails can cling to rubber
is why it’s so important to clean your equipment before leaving a lake or
stream -- and ask your friends and guests to do the same,” Wakeman says. “We
need everyone’s vigilance to help contain this invasive species.”
these prevention steps after leaving the water to keep Wisconsin streams
·Inspect and remove all mud and debris that might harbor snails
from your boots, waders, boats and other gear with a stiff brush. If possible,
rinse with tap water before leaving the river. If you are going home, let your
gear freeze for 6-8 hours or dry it in a warm place (85 degree Fahrenheit) for
24 hours to kill mud snails.
·Drain water from boat, motor, bilge, decoys and other water
containing devices before leaving water access (before launching, after loading
and before transporting on a public highway).
MORE INFORMATION CONTACT: Bob Wakeman, 262-719-0740; David Rowe 608-275-3282
Maryna Serdani, OSU Plant Clinic, Oregon State University, Corvallis, OR 97331;
Joshua J. Vlach, Oregon Department of Agriculture, Salem, OR 97301;
Kelly L. Wallis, Columbia Ag Research, Hood River, OR 97031;
Marcelo Zerillo, Colorado State University, Ft. Collins, CO 80523;
Tim McCleary and
Jeanne Romero-Severson, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556; and
Ned A. Tisserat, Department of Bioagricultural Sciences and Pest Management, Colorado State University, Ft. Collins, CO 80523
Serdani, M., Vlach, J. J., Wallis, K. L., Zerillo, M., McCleary, T., and Tisserat. N. A. 2013. First report of Geosmithia morbida and Pityophthorus juglandis causing thousand cankers disease in butternut. Online. Plant Health Progress doi:10.1094/PHP-2013-1018-01-BR.
Butternut or white walnut (Juglans cinerea L.) is native to the
eastern United States and southeastern Canada. The wood is used for paneling,
cabinets, and furniture while the nut kernels are sweet, buttery, and popular in
baking and candy-making. It is not commonly grown as a landscape tree.
In November 2011, the Oregon State University Plant Clinic received several
branches from a butternut tree growing in Lane Co., OR. The large tree
displayed sparse foliage and branch dieback (Fig. 1). The branches had small
holes and insect galleries associated with girdling cankers (Fig. 2). Eighteen
months later, the tree is still standing and the disease does not appear to have
progressed since 2011.
Fig. 1. Sparse foliage and branch dieback of butternut (Juglans cinerea) with thousand cankers disease in Lane Co., OR.
Fig. 2. Geosmithia morbida canker and walnut twig beetle galleries on butternut branch.
Microscopic examination revealed the presence of larvae and adults of the
walnut twig beetle (Pityophthorus juglandis) in the galleries (Fig. 3).
Geosmithia morbida, the cause of thousand cankers disease (TCD), was
consistently isolated from necrotic phloem at the canker margins. The ITS region
of the rDNA and the β-tubulin and methionine aminopeptidase genes of two
single-spore isolates were amplified and sequenced. Both isolates belonged to a
multi-locus haplotype group containing G. morbida isolates collected from
southern California walnut (J. californica) and Persian walnut (J.
regia) in California, and from black walnut (J. nigra) in Colorado,
Oregon, and Tennessee. Pathogenicity studies were not conducted; however,
pathogenicity of other isolates of G. morbida to butternut following
artificial inoculation has been demonstrated (4). Butternut readily hybridizes
with Japanese walnut (J. ailantifolia) and these hybrids, which may
closely resemble butternut, have been widely planted. Therefore, the identity of
the declining butternut was confirmed using chloroplast-cleaved, amplified
polymorphic sequence markers and nuclear microsatellite markers (1).
Fig. 3. Larvae of the walnut twig beetle (Pityophthorus juglandis) feeding in the cambium.
G. morbida and P. juglandis have previously been reported on black
walnut in Oregon as well as in eight other western states and four eastern
states (Virginia, Tennessee, North Carolina, and Pennsylvania) (4). The latter
four states fall within the native range of butternut. TCD has also been
confirmed on Arizona walnut (J. major) in Arizona and New Mexico as well
as on English walnut (J. regia), California black walnut (J.
californica), and Northern California walnut (J. hindsii)
in California (3). Butternut is a relatively slow grower and is already
seriously impacted in its native range by another canker disease (butternut
canker) caused by the fungus Ophiognomonia clavigignenti-juglandacearum
(2). As a result, it was added to the endangered species list in Canada in 2005.
Further damage to butternut by TCD in these regions could be very serious. To
our knowledge, this is the first report of natural infection of butternut by
G. morbida and P. juglandis.
1. McCleary, T. S., Robichaud, R. L., Nuanes, S., Anagnostakis, S. L.,
Schlarbaum, S. E., and Romero-Severson, J. 2009. Four cleaved amplified polymorphic
sequence (CAPS) markers for the detection of the Juglans ailantifolia
chloroplast in putatively native J. cinerea populations. Mol. Ecol.
Resour. 9:525-527. doi:10.1111/j.1755-0998.2008.02465.x.
2. Ostry, M. E., and Woeste, K. 2004. Spread of butternut canker in
North America, host range, evidence of resistance within butternut populations and
conservation genetics. Pages 114-120 in: Black walnut in a new century: Proceedings
of the 6th Walnut Council Research Symposium. July 25-28, Lafayette, IN. Gen. Tech.
Rep. NC-243. C. H. Michler, P. M. Pijut, J. W. Van Sambeek, M. V. Coggeshall, J.
Seifert, K. Woeste, R. Overton, and F. Ponder, Jr., eds. USDA Forest Service, North
Central Research Station, St. Paul, MN.
3. Tisserat, N., Cranshaw, W., Leatherman, D., Utley, C., and Alexander, K.
2009. Black walnut mortality in Colorado caused by the walnut twig beetle and
thousand cankers disease. Online. Plant Health Progress doi:10.1094/PHP-2009-0811-01-RS.
4. Utley, C., Nguyen, T., Roubtsova, T. V., Coggeshall, M. Ford, T. C., Grauke,
L. J., Graves, A. D., Leslie, C. A, McKenna, J., Woeste, K., Yaghmour, M. A.,
Cranshaw, W., Seybold, S. J., Bostock, R. M., and Tisserat, N. 2013. Susceptibility
of walnut and hickory species to Geosmithia morbida. Plant Dis. 97:601-607.