Re: Knapweed, an exotic plant killer

Hate to tell ya - we don't have thistle either. Not everything
(fortunately as it turns out) can take 3 months of blast furnace heat
and clay soil.

I thought I had garlic mustard for a minute, but when I saw the berries,
it turned out to be pigeonberry which is benign and beloved by my
birdies - who obviously planted it. After listening to Marge talk about
garlic mustard, it was fixin' to go in the burn barrel.


whew!

---------- Original Message ----------------------------------
From: "Kitty" <kmrsy@comcast.net>
Reply-To: gardenchat@hort.net
Date:  Thu, 11 Sep 2003 20:32:24 -0500

>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]
>> > >
>> > >---------------------------------------------------------------------
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>> > >
>> > >
>> >
>> > --
>> > Pam Evans
>> > Kemp TX/zone 8A
>> >
>> >
>> >
>> > --
>> >
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--
Pam Evans
Kemp TX/zone 8A



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