Monsanto Finally Admits to 
Creating 181 Roundup Resistant Superweeds

Monsanto Website 27aug2005

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Your Questions

Q: How widespread are glyphosate-resistant weeds in the United States?

August 27, 2005

A: The International Survey of Herbicide-Resistant Weeds <http://www.weedscience.org/in.asp> indicates that, globally, 181species of herbicide-resistant weeds can be found in approximately 270,000 fields. The Survey also indicates that resistance to glyphosate has been confirmed in 7 weed species, 4 in the U.S. In addition, Monsanto and the University of Georgia are investigating a probable case of glyphosate-resistant Palmer pigweed (Palmer amaranth) in central Georgia.

It is important to recognize that glyphosate-resistant species of greatest commercial significance in the U.S. are horseweed (marestail) (Conyza Canadensis), common ragweed (Ambrosia artemisiifolia) and rigid ryegrass (Lolium rigidum).

University scientists estimate that glyphosate-resistant horseweed can be found in 729 - 2052 fields in 11 states. As of August 27, 2005, university estimates of the acreage affected by glyphosate-resistant horseweed range from 112,866 - 1,122,615 acres or much less than one percent of U.S. corn, cotton and soybean acreage.

While horseweed-infested acreage is increasing, ninety-seven percent of the affected acreage is found in two states, Delaware and Tennessee. Growers in those states control horseweed with economical tank mixes. Pennsylvania State university weed scientists have constructed a map [below] of U.S. counties affected by glyphosate-resistant horseweed and Purdue University scientists are using Geographic Information Systems (GIS) <http://www.btny.purdue.edu/weedscience/marestail/index.htm> to describe that weed’s presence in Indiana.

Common ragweed is known to be in one Missouri soybean field and glyphosate-resistant rigid ryegrass inhabits less than 10,000 acres in California, mostly in almond and prune production areas.

source: http://www.weedresistancemanagement.com/layout/faq/faq_01.asp 3nov2005

Glyphosate Resistant Conyza canadensis L. in the Eastern United States — by county

Compiled by Dauer (PA) from information provided by Patterson (AL), Smith (AR), Van Gessel (DE, MD), Barnes (IN), Johnson (IN), Rogers (KY), Ritter (MD), Kendig (MO), Koger (MS), York (NC), Majek (NJ), Stachler (OH), Loux (OH, IN), Curran (PA), Hayes (TN). Updated 7 Dec 2004. If there is additional information to be added, please email Joe Dauer at jtd152@psu.edu 

source: http://cropsoil.psu.edu/weedecology/personnel/Dauer/research%20pages/CountySpreadGRhorseweed3.jpg 3nov2005