[NAFEX] article on white pine blister rust in the Northeast
Sam.Brungardt at state.mn.us
Mon Nov 29 10:03:05 EST 2004
While the article did not include the reader's question, one can surmise
that it was about seeing misshapen or dying white pine trees. The
author mentions the Canadian hybrid black currants, but not Titania, a
more recently developed cultivar whose propagation is restricted. -- Sam
The original version of this article from Barre Montpelier (Vermont)
Times Argus can be seen at www.timesargus.com.
Article published Nov 28, 2004
Furlough for the forbidden fruit
Chances are you have seen a victim of white pine blister rust. I think
it's safe to say that most big dead white pines - the ones with the
remains of large crowns, not those that were slowly squeezed out by
their neighbors - have this fungus to blame for their demise.
The transportation of tree diseases across the globe is not a new
phenomenon. This fungus, one of the first introduced tree diseases -
and for white pines, easily the worst - began its journey from its
native Russia to North America in 1705. The first move was when our
much-admired white pines were shipped from New England to the estate of
Lord Weymouth in England. There they were renamed Weymouth pines and,
by the mid-1800s, had been widely planted in Europe as well as in
England. When a Russian pine infected with blister rust was shipped
west, the disease afflicted European Weymouth pines. It went on to the
United States in the late 1800s, when American nurseries ran short of
home-grown white pine seedlings to use in reforestation efforts and
imported infected Weymouth pine seedlings.
Blister rust spreads quickly. By the early 1900s, white pines
throughout Vermont and New Hampshire were infected and dying. This
fungus is true to its name: It attacks white pine, causes blisters, and
has rust-colored spores in one of the stages of its complicated
Five different types of spores are produced during the life cycle of
this fungus, and three of them can only survive and reproduce on
currants and gooseberries, which make up the genus Ribes. The disease
does not spread from one pine to another: It must complete part of its
life cycle on a Ribes plant. Spores produced on the leaves of Ribes
then travel back to pines and infect the trees by entering the tiny
holes in the needles called stomata.
In an attempt to control the disease, the cultivation of Ribes was
banned soon after blister rust was introduced, and crews were sent into
the woods to tear up wild Ribes plants or treat them with herbicides.
If there are no currants or gooseberries close to white pines, there
will be no new cases of white pine blister rust. On paper, it looked
like a winning strategy.
Roughly $150 million or more has been spent on destroying Ribes to save
pines. An unknown amount of money also has been spent on programs to
breed resistance into both white pine and Ribes. In 1949, for example,
more than $6.5 million was appropriated for Ribes eradication. Fifty
years ago, 95 percent of the $3.8 million spent on controlling forest
diseases was aimed at blister rust.
Eliminating wild Ribes in areas where blister rust is most damaging -
mainly cold, damp environments - has not been extremely effective. If
even a few Ribes plants survive, the infection rate remains high.
Eliminating Ribes from non-hazard areas, on the other hand, is
considered unnecessary, because there the disease occurs infrequently
regardless of the number of Ribes bushes.
In most states in the Northeast, eradication programs and laws banning
the planting of Ribes plants have now been rescinded or are no longer
enforced. Eradication programs have been abandoned because they seem
futile. One reason for this is that the seeds of many native Ribes
species may lie dormant for years before sprouting; another is that
plants can grow back from small pieces of their roots.
So the pendulum has now swung to the side of those who like their
currant juice and jelly. And there is more good news for berry
aficionados. Several Ribes varieties have been bred that are resistant
to blister rust. The black currants Consort, Coronet, and Crusader do
not become infected, and farmers and gardeners throughout the Northeast
have expressed an interest in growing them. Some foresters are a little
worried about this, however, pointing out that these resistant cultivars
are also non-native species and will inevitably interbreed with native
species. The progeny from these crosses will be disseminated across the
landscape, and subsequent generations may have little resemblance to
their parents with respect to their resistance to blister rust.
Finding a balance between the goals of forestry and those of farming -
with currants being restricted to certain areas, perhaps - will require
cooperation and communication. If that happens, we can have both black
currant jelly and a nice set of pine shelves on which to store the jars.
Virginia Barlow is an editor of Northern Woodlands magazine in Corinth.
The illustration for this article is provided by Adelaide Tyrol.
Support for this series is provided by the Upper Valley Community
Foundation's Wellborn Ecology Fund: wef at nhcf.org.
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