[APWG] Roadside herbicide use may be creating super weeds?

[Marc Imlay]

Thanks Craig.

We typically remove about 90% of the population with herbicide and hand
remove the rest that is mixed with natives at the edge of the population.

Marc

-----Original Message-----
From: Craig Dremann [mailto:craig at astreet.com] 
Sent: Tuesday, August 21, 2007 10:32 AM
To: Marc Imlay
Cc: apwg at lists.plantconservation.org
Subject: Roadside herbicide use may be creating super weeds?

Marc Imlay wrote:
> 
> That is why it is our policy to remove all members of a population. Thus
there can be no "natural" selection.
> 
> Marc Imlay, PhD
> 

Dear Marc and All,

Like a microscopic bacterial pathogen, perhaps we could  look at exotic
weeds like a macroscopic pathogen, and our herbicides are macroscopic
antibiotics?

Then, perhaps the weed populations that we are fighting in wildlands
situations, may have originated and been selected, from interactions
between the species and herbicides, either in adjacent cultivated
fields, or more likely, along roadsides that are maintained using
herbicides?

One of the Caltrans representatives, a member of our County Weed
Management Area team, reported last year that the maintenance workers
are seeing certain perennial plant populations become immune to all of
the herbicides sprayed along our county's roadsides every year.

I've also seen this happening along most of Southern California's 
roadsides, with the escaped ornamental Fountain grass that is
herbicide-resistant--it eats the herbicides for breakfast, and uses the
sprayed bare roadsides, as its new habitat---and then moves into the
adjacent wildlands when its numbers reach critical mass.

Perennials are probably the most likely weeds to develop resistance
first, and perhaps it would be useful for an agency like the EPA to fund
a grant, to survey each state's highway maintenance workers, to see how
big of an issue this might be, and how many species have become
resistant?

Then, like overuse of antibiotics which cause bacteria to become
resistant, we may have to limit use of herbicides in certain situations,
so we don't develop "super weeds", like the southern California fountain
grass?

Sincerely,  Craig Dremann (650) 325-7333