Subject: Re: Demise of natural Cattails?
From: wtmorgan@pilot.msu.edu (Bill Morgan)
Organization: Michigan State University
Date: Mon, 01 Sep 1997 14:03:10 -0400
Message-ID: <MOD$970901.5713@rec.gardens.ecosystems>
References: <MOD$970830.8016@rec.gardens.ecosystems> <MOD$970831.15104@rec.gardens.ecosystems>
In article <MOD$970831.15104@rec.gardens.ecosystems>, William D Hulet
wrote:
> On Sat, 30 Aug 1997 OperaGoer@webtv.net wrote:
>
> >
> > There has been recent press concerning the weed from a
> > european-introduction that prefers the low ditches and watery areas but,
> > while it has lavender blossoms and is attractive, it is very rapidly
> > replacing our natural cattails.
> > what possible consequence may this have on our delicate eco-system? What
> > birds, insects, animals, etc., depend upon these for part/all of their
> > existence?
>
> If you mean purple loosestrife, it is a scary thing to watch. It
> had/has totally over-run a lot of wetlands here in Southern Ontario. [snip]
You got that right. Very frightening, aggressive. Only the giant grass
Phragmites comes close as a wetlands invader. Here in mid Michigan, it is a
major problem.
And yes, in destroying not just cattails, but much wetlands vegetation, it
does remove resources utilized by birds, small mammals, insects, etc.
>
> The local university's bio-control labratory has a program where
> local enviro-types can pick up some European beetles that eat the stuff in
> exchange for doing some simple records keeping. [snip]
Here at Michigan State U, I know a few people who are working with a
similar project, now in the phase of doing test releases of beetles to
control loosestrife.
Amazingly, there are people who object to this because "it's such a pretty
flower." And it's not like it will ever be eliminated, either. If it is
knocked back 90-95%, the people working on control will declare victory and
go home. So the "pretty flower" will be here for a long time to come.
Still, complaints come in. I guess one must consider the source.
> But there's a bit of controversy about
> whether we should be bringing another exotic to deal with the first one.
There's always a risk when this is done. Unfortunately, there are some real
good examples of introduced biocontrol gone awry. Much of this happened
decades ago, and was the result of people not testing the "control"
organism, or in some cases of not even researching the basic biology. So
you get an introduced snake on some island and it is eating bird's eggs.
The birds have never dealt with snakes and have no behavioral defenses.
They're going down the tubes fast. You intoduce the mongoose, which eats
snakes.
But also eats bird's eggs...
More recently, a weevil introduced to control musk thistle has been
devestating the rare Platte thistle and some other native thistles.
At a certain point, biocontrol is like surgery to remove a cancer or
gangrene. It sure ain't good to lop off body parts, but it may be better
than letting the whole body die. (i.e, it is an imperfect solution).
>
> I suspect that part of the anxiety about loosestrife is its
> extreme visibility. If it didn't convert wetlands into bright pink
> blotches, it might not have people so pumped up. (One of the scientists
> involved told me that he's seen another exotic---"yellow canal grass"---
> filling in some of the void left by the loose strife. As he said "one
> problem at a time".)
And things will never be like they used to be. In time, many of these
introduced pests may acquire their own natural enemies whether or not we
import them. They will be big targets because they are so abundant and
well, evolution marches merrily along. The question is what damage is done
while we are waiting for natural processes to take care of the aliens, and
how long we can afford to wait while doing nothing.
BTW: not just aggressive plants pick up new natural enemies. Five hundred
years ago, the apple maggot did not exist. But as apples became a common
crop in North America, hawthorn maggots found it an acceptable alternative
to hawthorn (aka thornapple). Eventually, the species split and now the
apple maggot is a separate full-fledged species, and a native pest of an
alien crop. A third fly, whose maggots feed on domestic (Old World)
cherries is also coming out of this mix.
So yes, there are problems with biocontrol, and new alien invaders keep
cropping up all the time. Unfortunately, we can't just turn our backs,
pretend it's not happening, and just do nothing.
Regards,
Bill
--
Bill Morgan
wtmorgan@pilot.msu.edu
Center for Room Temperature Confusion