Re: Knapweed, an exotic plant killer

Good grief!
Hives and aftertaste too!  This nasty really has all sorts of defences.
Kitty

----- Original Message ----- 
From: "Betsy Kelson" <bkelson@ix.netcom.com>
To: <gardenchat@hort.net>
Sent: Thursday, September 11, 2003 6:29 PM
Subject: Re: [CHAT] Knapweed, an exotic plant killer


> Pam,
>     I do not think it hates heat. It did not slow down much in last year's
> Colorado drought. I have been pulling a small patch of this nasty at the
top
> of my driveway for 4 years now and have it under control. You CAN control
it
> with hand pulling, because nothing on a typical garden center shelf will
> touch that fuzzy blue green foliage.
>     I belong to a Weed Wacker Group that is trying to control noxious
weeds
> around our Community's  Lake. About 500 yards along the road(this weed
loves
> roadsides) was highly infested with knapweed 6 years ago. This year, we
only
> filled about 3 bags with the stuff. The other 6 bags were filled with
Canada
> Thistle(another nemesis that we will never eradicate). There is so little
to
> pull that the group will be starting on another area of the stuff next
year.
> HOO HOO!!!
>     A word of warning though. I am not allergic to very many things, but I
> must wear long sleeves in the summer when I pull this nasty or I get hives
> all along my arms. I can also taste this thing after a good hour of
pulling
> so be careful out there
>
> Betsy
> evergreen co
> it was 34 degrees at 7 this morning yikes!!
> ----- Original Message -----
> From: "Pamela J. Evans" <gardenqueen@gbronline.com>
> To: <gardenchat@hort.net>
> Sent: Wednesday, September 10, 2003 9:15 AM
> Subject: Re: [CHAT] Knapweed, an exotic plant killer
>
>
> > HOW AWFUL!
> > I'm going to look for a picture of this monster.
> > Hope it hates heat.
> >
> > ---------- Original Message ----------------------------------
> > From: "Bonnie Holmes" <holmesbm@usit.net>
> > Reply-To: gardenchat@hort.net
> > Date:  Wed, 10 Sep 2003 09:18:53 -0700
> >
> > >Thought you might find this interesting since it can kill other garden
> plants.
> > >September 9, 2003
> > >Forensic Botanists Find the Lethal Weapon of a Killer Weed
> > >By CAROL KAESUK YOON
> > >or over a century, spotted knapweed has been a growing scourge on the
> > >North American landscape, spreading across millions of acres of
> > >prairies, hillsides, roadsides and rangeland  pretty much anywhere it
> > >can get a root in the dirt. Everywhere it spreads, it replaces native
> > >grasses and other plant species to the consternation of
conservationists
> > >as well as ranchers, whose cows refuse to eat it.
> > >
> > >The weed, which sprouts pink and purple flowers and can grow a spindly
> > >three feet tall, is a European import, thought to have been introduced
> > >in North America as a contaminant in crop seeds or in dirt used as
> > >ship's ballast and then dumped. But scientists have long been baffled
by
> > >the plant's appalling effectiveness at driving out other plants.
> > >
> > >Now in the current issue of the journal Science, researchers say they
> > >have found spotted knapweed's deadly secret: a potent and previously
> > >unknown poison that it releases through its roots into the soil to kill
> > >off neighboring plants. By eliminating its neighbors, the weed can
> > >appropriate all the water and nutrients that the other plants would
have
> > >taken, and it has plenty of new space to spread out in.
> > >
> > >Dr. Jorge M. Vivanco, a plant biologist at Colorado State University
and
> > >an author of the study, says the toxin acts so quickly that within 10
> > >seconds of contact the neighboring plants' roots begin producing
> > >chemicals that set off a cascade of events that will ultimately kill
> > >their own cells.
> > >
> > >"In one hour the roots die," he said. "The whole plant dies in a matter
> > >of days." The substance is such an effective herbicide that, Dr.
Vivanco
> > >said, his university had already taken out a patent on it.
> > >
> > >Scientists often assume that invasive exotic species are able to thrive
> > >in new environments because they have escaped from their predators and
> > >other enemies at home. But scientists say the new study suggests that
> > >such troublesome imports may also succeed by using potent but
> > >unrecognized methods, like chemical warfare.
> > >
> > >"This is a really nice demonstration that other factors come into
play,"
> > >said Dr. Sarah Reichard, an invasion biologist at the University of
> > >Washington. "This paper shows that the interactions can be very subtle,
> > >things happening below ground that we really haven't had any knowledge
> > >about."
> > >
> > >The notion that plants use poisons to suppress or kill their neighbors

> > >a phenomenon known as allelopathy  has been around for decades. But
> > >until now, few scientists have had much use for it.
> > >
> > >"People have been rather dismissive of the whole subject," said Dr.
> > >Alastair Fitter, an ecologist at the University of York who was not
> > >involved in the study.
> > >
> > >Part of the problem was that much of the earliest work was poorly done,
> > >he said in a telephone interview. But as Dr. Fitter wrote in an
> > >accompanying commentary in Science, he believes the new study is so
> > >convincing that it will "now place allelopathy firmly back on center
> > >stage."
> > >
> > >The researchers found that the roots of the spotted knapweed released
> > >two forms of a chemical known as catechin (pronounced KAT-uh-kin)
> > >identical in all respects except that their molecular structures were
> > >mirror images of each other.
> > >
> > >One form, known as +catechin, is also found in green tea and was
already
> > >known as an antioxidant, able to neutralize the harmful molecules
called
> > >reactive oxygen species that are thought to speed the aging process.
> > >
> > >The toxin turned out to be the second form, -catechin, which had
> > >essentially the opposite effect of its mirror image. It induced the
> > >production of harmful reactive oxygen species in neighboring plant
> > >roots, setting off the process that led to cell death.
> > >
> > >The finding helps explain the failure of many efforts to fight the
> > >onslaught of spotted knapweed by burning it and then seeding the area
> > >with desired plants.
> > >
> > >"What they've seen is that 99 percent of the seeds died, and now we
know
> > >why," said Dr. Vivanco. With -catechin soaked into the soil, he said,
> > >susceptible seeds have no chance of making it.
> > >
> > >But even though the poison is very powerful, it remained unknown to
> researchers because everything was happening below ground.
> > >"One plant arrives in a field where there are a lot of native plants,"
> > >Dr. Vivanco said. "The next year you see not one, but actually a patch
> > >of spotted knapweed where the natives were. And if there are still
> > >native plants near it, they don't look so healthy."
> > >
> > >Around Missoula, Mont., home of the University of Montana, for example,
a
> diversity of native species once bloomed.
> > >Now after several decades of this subtle underground warfare, the hills
> > >have become a vast monoculture of spotted knapweed, Dr. Vivanco said,
as
> > >have millions of acres in that particularly hard-hit state.
> > >
> > >The scientists found that the grasses that grow alongside spotted
> > >knapweed in Europe are much better able to resist its toxins than
native
> > >North American grasses. Scientists say this suggests that the European
> > >grasses have evolved a resistance to this potent toxin, one that North
> > >American grasses lack.
> > >
> > >Since spotted knapweed landed in North America, a century or so ago, it
> > >has spread to nearly every state and has caused a variety of problems.
> > >
> > >Eric Lane, the state weed coordinator for Colorado, said the loss of
> > >native plant species curtailed the food supply not only for cattle but
> > >for wild species like elk, many birds and insects. In some states, he
> > >said, the spread of spotted knapweed is so severe that elk herds have
> > >altered migration pathways to avoid vast inedible swaths of it.
> > >
> > >The weed has also led to erosion because it does not hold soil as well
as
> native grasses.
> > >In the search for solutions to this green plague, researchers were
> > >excited to discover that the plant Arabidopsis thaliana, whose entire
> > >genome has already been sequenced, is susceptible to -catechin. As a
> > >result, they can see in detail how a plant's genome reacts when its
> > >roots are hit with the toxin.
> > >
> > >The scientists found 10 genes that appear to shift into high gear
> > >immediately. Scientists say they hope that by identifying what those
> > >genes are doing, presumably mounting the beginnings of a defense, they
> > >can genetically engineer plants that can more effectively resist the
> > >spotted knapweed's attacks.
> > >
> > >Researchers are also testing to see what native plants are resistant to
> > >the -catechin. They hope to develop a list of species that can be used
> > >to revegetate an area after spotted knapweed has been burned.
> > >
> > >So far, the researchers have found no native plants that can withstand
> the poison.
> > >
> > >
> > >Copyright 2003 The New York Times Company
> > >
> > >Bonnie Zone 6+ ETN
> > >
> > >[demime 1.01d removed an attachment of type image/gif which had a name
of
> f.gif]
> > >
> > >---------------------------------------------------------------------
> > >To sign-off this list, send email to majordomo@hort.net with the
> > >message text UNSUBSCRIBE GARDENCHAT
> > >
> > >
> >
> > --
> > Pam Evans
> > Kemp TX/zone 8A
> >
> >
> >
> > --
> >
> > ---------------------------------------------------------------------
> > To sign-off this list, send email to majordomo@hort.net with the
> > message text UNSUBSCRIBE GARDENCHAT
>
> ---------------------------------------------------------------------
> To sign-off this list, send email to majordomo@hort.net with the
> message text UNSUBSCRIBE GARDENCHAT

---------------------------------------------------------------------
To sign-off this list, send email to majordomo@hort.net with the
message text UNSUBSCRIBE GARDENCHAT
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index