Resistance Prevention

Scouting Michigan fields for Palmer amaranth

Scouting will be key to stopping the spread of glyphosate-resistant Palmer amaranth in Michigan.


It has been almost three years (fall 2010) since Palmer amaranth resistant to glyphosate (Roundup) and ALS-inhibiting herbicides was first reported in Michigan.  Initially, populations of this weed appeared to be localized to parts of St. Joseph and Kalamazoo counties. However, last summer more populations of Palmer amaranth were confirmed in nine Michigan counties: St. Joseph, Kalamazoo, Cass, Barry, Ionia, Clinton, Shiawassee, Gratiot, and Livingston.  This weed is not native to Michigan and with resistance to glyphosate and other effective herbicides this weed is undoubtedly the toughest that Michigan growers have ever faced.  In fact, in many Southern states where this weed is a problem it has been reported that the average increased cost to manage this weed ranges from $30 to $50 more per acre.


May 30, 2013

read »

2016 Status of Herbicide Resistant Weeds in Michigan

In the fall of 2015 the herbicide resistance screening returned to Diagnostic Services, after spending many successful years under the direction of Dr. Christy Sprague. The 2015 season saw a surge in submissions, with a total of 46 samples (a 40% increase over 2014). The samples included...


June 2, 2016

read »

2017 Status of Herbicide-Resistant Weeds in Michigan

In 2016 yet another record number of plant samples were submitted for herbicide resistance screening to MSU Diagnostic Services. Seventy samples were submitted in total, a 52% increase over 2015. 


May 15, 2017

read »

Postemergence herbicide applications in corn- Residual option

Studies conducted at Michigan State showed the highest yields and greatest weed control were observed where a residual herbicide was applied preemergence and followed by either glyphosate or glufosinate postemergence.

June 3, 2010

read »

2015 Status of herbicide resistant weeds in Michigan

Each fall we receive several weed seed samples from around the state to test for resistance to various herbicides. All testing is conducted by the weed science group within the Department of Plant, Soil, and Microbial Sciences at MSU and is sponsored by the Michigan Soybean Promotion Committee. In 2014 we received samples of redroot pigweed (1), Palmer amaranth (2), common waterhemp (5), common ragweed (7), common lambsquarters (2), and horseweed/maretail (15). Each sample received is tested for resistance to five or six herbicide Sites of Action. 


Posted April 23, 2015

read »

Early management is important for horseweed control in soybean

Glyphosate-/multiple-resistant horseweed (marestail) is fairly common in many of Michigan’s no-till soybean fields. In fact, of the 12 horseweed samples that we tested this winter for resistance all showed some sort of resistance. Nine were multiple-resistant to glyphosate (Group 9) and ALS-inhibiting herbicides (Group 2), two were resistant to glyphosate only, and one was resistant to the ALS-inhibitors only. Because of resistance problems...


Posted April 30, 2015

read »

Palmer amaranth: Managing this new weed problem (Progressive Forage Grower 2014)

Herbicide-resistant Palmer amaranth continues to invade many areas of Michigan and the Upper Midwest. Our first encounter with Palmer amaranth in Michigan occurred in the fall of 2010.

A soybean producer in southwest Michigan was struggling with management of a weed he did not recognize. We were able to identify this weed as Palmer amaranth, and through greenhouse testing confirmed high levels of resistance to both glyphosate (Roundup) and ALS-inhibiting herbicides.

At this time, we also noticed several neighboring alfalfa fields where Palmer amaranth seed heads were poking just above the alfalfa canopy....


May 1, 2014

read »

Horseweed confirmed resistant to glyphosate in Michigan field crops

This past winter two horseweed samples suspected of being resistant to glyphosate were screened and were confirmed resistant to glyphosate. These samples were collected from a no-till soybean  field and a stale seed-bed sugarbeet field in Ionia and Gratiot counties. These are the first reports of confirmed glyphosate-resistant horseweed in Michigan field crops.

April 14, 2011

read »

Consider the addition of a resicual herbicide with burndown treatments in no-till soybean

Reduced glyphosate costs make it tempting to rely only on glyphosate for weed control in no-till Roundup Ready soybean. However, the addition of a residual herbicide with burndown herbicide applications can provide many benefits.

April 29, 2010

read »

Glyphosate-resistant and some glyphosate- and ALS-resistant horseweed found in Michigan fields: Early management is important

In 2010 two horseweed samples suspected of being resistant to glyphosate were collected from a no-till soybean field and a stale seed-bed sugarbeet field in Ionia and Gratiot counties were confirmed resistant to glyphosate. In 2011 six additional horseweed samples from Lapeer, Clinton, and Washtenaw counties were confirmed resistant to glyphosate and some of these samples are multiple resistant to glyphosate and ALS-inhibitors (FirstRate and Classic), which makes this weed extremely difficult to control in soybean.


April 12, 2012

read »

Postemergence herbicide application in corn- It's all about timing

The development of stacked trait technology and the increased interest in herbicide tolerant corn has led to an increase in postemergence herbicide applications for weed control. Postemergence programs without a residual herbicide applied at planting have their place, and can provide excellent season long weed control. However, important considerations that should be made include timing, herbicide resistance, and management strategies.

June 4, 2010

read »

Free screening for glyphosate-resistant weeds in Michigan

Confirming herbicide-resistant weed populations is the first step of any resistance management program. Verification will provide producers with the knowledge to implement the best possible management strategies, with the ultimate goal of preventing or limiting the spread of herbicideresistant weeds.

September 23, 2010

read »

Flexstar GT: A new herbicide for postemergence use in Roundup Ready soybean

Specific weeds this premixture may help with control are pigweeds, eastern black nightshade, and common and giant ragweed. Additionally, using the two different herbicide modes of action found in Flexstar GT may also reduce the risk of the development of herbicide-resistant weeds.

May 7, 2009

read »

Soil-applied residual herbicide benefits in soybeans

The use of postemergence (POST) glyphosate in Roundup Ready soybeans has been the primary weed control program used by many Michigan soybean growers. While this system has seemed to simplify weed management, relying on total postemergence herbicide programs can be difficult to manage if not properly implemented.

April 26, 2007

read »