Emerging Weed Issues

Glyphosate-resistant Palmer amaranth confirmed in Southwest Michigan

Palmer amaranth, a weed not common to the northern U.S. has been identified and confirmed resistant to glyphosate in Southwest Michigan.

April 26, 2011

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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

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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

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Dry conditions will likely impact herbicide carryover to rotational crops

Dry conditions this growing season throughout most of the state have not only affected the current crop, but will likely impact rotational crops including wheat and cover crops planted this fall. Reduced soil moisture following a herbicide application (especially in the first 2-4 weeks) can slow the degradation (breakdown) of herbicides, resulting in the potential for carryover. Additionally, lack of soil moisture can also result in increased herbicide adsorption to soil particles and organic matter, reducing herbicide availability for degradation. 

 

July 27, 2012

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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

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Dodder: A potential new weed problem

Recently, the parasitic weed dodder was found in a Michigan field that was frost seeded to clover. Dodder infestations can reduce yield and weaken host plants making them more susceptible to other pests and diseases that may eventually kill the host.

September 23, 2010

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New seeding of Roundup Ready alfalfa halted

As some of you are likely aware, a U.S. District Court in California has issued a temporary injunction that prohibits the planting of Roundup Ready alfalfa after March 30, 2007. This injunction was in response to arguments made against the procedures the USDA followed prior to deregulating glyphosate-resistant alfalfa in June 2005.

March 22, 2007

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Keeping stacks straight- Part II, Tips to reduce 'Trait Torture'

Every season there more transgenic traits and stacks, and new brand names to add to the confusion. Below is a top-ten list of things you can do to avoid mistakes at planting, and to help diagnose field problems later in the season.

April 30, 2009

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Weed control challanges for sugarbeet in 2008

After a long wait Michigan sugar beet growers will be growing Roundup Ready sugar beets for the first time this year. While for most of us the use of glyphosate (Roundup) in Roundup Ready sugar beets should make weed control simpler and more consistent. However, as with any changes in production practices there will be a learning curve to using this technology.

April 2, 2008

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Challenges and options for giant ragweed management

Giant ragweed is an early germinating, summer annual weed species that is commonly found throughout the southern two tiers of Michigan counties and throughout many areas of the Midwest. Surveys conducted in several Michigan counties this year ranked giant ragweed one of the most problematic and common weed escapes in both corn and soybean fields.

April 12, 2007

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Corn hybrids stressed after glyphosate applications

Corn growers who have planted Roundup Ready hybrids should be aware that five hybrids have shown stress symptoms after glyphosate applications; however, the symptoms are primarily due to environmental stresses.

June 19, 2008

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Avoid herbicide spray tank contamination

Later planted and replanted crops have put us in the situation where postemergence herbicide applications will be made to several different crops during the same time period. Because of the vast number of acres that need to be sprayed with different types of products, caution needs to be taken to avoid spray tank-contamination.

June 22, 2006

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Don't forget AMS with glyphosate

There are over 280 products (commercial and ready-to-use) with glyphosate currently registered for use in Michigan. One of the main differences among the many available products is the surfactant component of the formulated products; some may need additional surfactant while others do not.

May 11, 2006

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Challenges and options for giant ragweed management

Giant ragweed is an early germinating, summer annual weed species that is commonly found throughout the southern two tiers of Michigan counties and throughout many areas of the Midwest. Surveys conducted in several Michigan counties this year ranked giant ragweed one of the most problematic and common weed escapes in both corn and soybean fields.

April 12, 2007

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New herbicide options in corn and soybean

Since the release of the 2008 Weed Control Guide for Field Crops, several new herbicides have been registered for the 2008 growing season in corn and soybean.

March 20, 2008

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Challenges and options for giant ragweed management

Giant ragweed is an early germinating, summer annual weed species that is commonly found throughout the southern two tiers of Michigan counties and throughout many areas of the Midwest. Surveys conducted in several Michigan counties this year ranked giant ragweed one of the most problematic and common weed escapes in both corn and soybean fields.

April 12, 2007

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