Weeds In Waiting

Giant ragweed

This winter, dealers and growers may be trying to decide if dry weather, herbicide resistance, or poor application timing caused unacceptable weed control last year. No matter the cause, more weeds in the seed bank will mean more plants in 2008, says Jeff Stachler, Extension program specialist with The Ohio State University.

Bill Johnson, weed specialist with Purdue University, says a dry spring in Indiana in 2007 led to erratic and sometimes poor performance of soil-applied herbicides, as they weren’t activated by rainfall. “And it was so hot and dry later that weeds that are a problem to control anyway — including common lambsquarters, giant ragweed, and morningglory — weren’t controlled because they were hardened off by the drought.”

Ohio saw a similar weather and control scenario, reports Stachler. Giant ragweed hit corn hard, while soybean fields also saw common ragweed, common lambsquarters, velvetleaf, and common pokeweed.

Could resistance be playing a role? “I think glyphosate resistance is confusing to growers compared to ALS resistance,” says Johnson. “Glyphosate resistance is difficult to diagnose because we are dealing with low levels of resistance. This means that weeds will be injured by glyphosate, and whereas ALS resistance is clear-cut, weeds show very little injury by a glyphosate herbicide. Growers often think their herbicide failure is weather-related, or a result of a misapplication, and they may be surprised at how much resistance is out there.” Fourteen counties in Indiana now have confirmed glyphosate resistance in giant ragweed, and the problem will only continue to expand if growers do not manage this weed more aggressively, he says.

In addition, it appears that increasing percentages of Indiana’s growers planting glyphosate-tolerant corn were not using residual herbicides or lower rates of residual herbicides.

“I have a great deal of concern about the minor yield losses that are occurring because of early-season weed competition before glyphosate is applied in corn, and the growers may be thrilled with 200 bushels per acre corn when they could have had 210 to 220 with a more aggressive approach to weed management,” he says.

Johnson hopes that because corn prices were high, growers can invest some of that income on these products “to get 10 to 15 more bushels per acre this year.”

Johnson is encouraged that residual herbicide use is, in general, higher in corn than in soybeans. “The problem with corn is that there is such a narrow window to put on postemerge products, because the crops outgrow sprayers or labels,” he says. Plus, weed infestations can be difficult to see from the road.

For 2008, “we’ve had plenty of precipitation, our groundwater has been recharged, and we’re going into spring with normal soil moisture.” That’s good news for soil-applied herbicides.

Ragweed and Volunteer Problems

“Giant ragweed has the greatest potential to be a problem in Ohio because of how much went to seed in corn and soybeans due to improper application timing and herbicide resistance,” says Stachler. He also anticipates a ragweed problem as growers switch back to normal soybean acreage in 2008. “The giant ragweed that went to seed last year in corn will cause more problems in soybeans because some will be resistant,” he explains. In fact, he’s seen more stacked resistance: ALS/glyphosate-resistant giant ragweed, common ragweed, and marestail.

Officially, glyphosate resistance has not been documented in Iowa, but there are plenty of stories throughout the state “that strongly support the supposition that resistant weed populations exist in Iowa,” says Michael Owen, Extension weed management specialist, Iowa State University. Suspects for resistance include giant ragweed, marestail, and common lambsquarters, but recent control problems with common waterhemp should also concern growers.

Use of glyphosate has also caused volunteer crop management issues, Owen says. Spring conditions in Iowa in 2007 were not ideal, calling for replanting in many corn acres. Growers had to make sure to destroy stands that possessed herbicide resistance traits.

“I view volunteer Roundup Ready (RR) corn as a huge problem,” says Kevin Bradley, Extension weed specialist at the University of Missouri. And Dawn Refsell, University of Illinois Extension specialist, says her growers may see more volunteer RR corn in both corn and soybeans.

Waterhemp Woes

The “comer” weed for 2007 in both Illinois and Missouri seemed to be waterhemp. “Our newest problem is glyphosate-resistant waterhemp,” says Refsell. “This weed is going to change how we currently manage our soybean acres. We’ll no longer be able to rely on total postemergence glyphosate applications — growers are going to need the addition of preemergence chemicals and tank mixes.”

Velvetleaf may be showing some ALs resistance, causing trouble for soybean growers.elvetleaf may be showing some ALs resistance, causing trouble for soybean growers.
Velvetleaf may be showing some ALs resistance, causing trouble
for soybean growers.elvetleaf may be showing some
ALs resistance, causing trouble for soybean growers.

Illinois also faces combination resistances in waterhemp in the ALS, triazine, and PPO chemical classes; “our options for controlling waterhemp in soybean are getting limited to preemergence products only,” he explains.

“It would only help our situation if in fact we have less soybean planted next year,” says Missouri’s Bradley. “I’m not sure that’s going to happen. We’re a heavy soybean state, and we had a slight drop in soybean acreage last year but not as much as expected.”

In 2008, growers in Illinois should also be on the lookout for common lambsquarters, giant ragweed, morningglory, and marestail. Bryan Young, professor of weed science at Southern Illinois University, reports these weeds, as well as waterhemp, saw inconsistent foliar control with glyphosate products. He says: “I’m afraid we may have widespread problems in 2008.”

Cotton Concerns

In North Carolina, glyphosate-resistant Palmer amaranth has been identified in at least 11 counties, says Alan York, Extension specialist, North Carolina State University. “Unfortunately, ALS inhibitors in cotton have always been marginal on Palmer, and ALS-resistant Palmer is widespread in the Southeast. That exacerbates glyphosate resistance concerns,” he says.

But York is encouraged that growers did better with the weed in 2007 than 2006, and believes better control came from “a greater awareness of the problem and greater use of other herbicides within Roundup Ready systems – plus rotating out of some bad fields.”

Indeed, North Carolina cotton acreage was cut roughly in half in 2007 as more growers planted corn. York says the switch may have helped, as good control options are available in corn. Cotton acreage will likely drop again for 2008, with wheat being planted in highway medians and “everywhere else this winter,” says York — followed by double-cropped soybeans, also a crop with some good Palmer control choices. “The good — or bad — thing about weeds,” he notes, “is that they will handle whatever weather we have pretty well. That gives guys like me job security.”

Leave a Reply

Herbicides Stories

Corn Field
HerbicidesNew Wilbur‐Ellis Herbicide Targets Volunteer Corn
April 28, 2016
Wilbur‐Ellis Co., a recognized leader in marketing and distribution of crop protection products, as well as precision agriculture technology, has Read More
HerbicidesHELM AGRO Launches New HELM Sulfentrazone 4F Herbicide
April 26, 2016
HELM AGRO US, Inc. has announced the federal Section 3 registration of its new HELM Sulfentrazone 4F herbicide. Classified as a Read More
HerbicidesHerbicide Resistance In Waterhemp Continues To Grow
April 22, 2016
Twenty-five years ago, waterhemp was virtually unknown to Illinois farmers. Today, the broadleaf weed blankets corn and soybean fields across Read More
Soybean Field
HerbicidesHELM AGRO US Unveils New Sheridan 25 WG Herbicide
April 22, 2016
HELM AGRO US, Inc. has announced the federal Section 3 registration of its new Sheridan 25 WG herbicide for selective Read More
Trending Articles
Eric SfiligojMissing The Family Ties In Agriculture
April 25, 2016
By its nature, the agriculture market is cyclical. Up and down cycles come and go with a regular pattern. For Read More
HerbicidesHerbicide Resistance In Waterhemp Continues To Grow
April 22, 2016
Twenty-five years ago, waterhemp was virtually unknown to Illinois farmers. Today, the broadleaf weed blankets corn and soybean fields across Read More
Eric SfiligojBiotech Corn Drop More Economics Vs. Consumer Rejection
April 18, 2016
Since their introduction into the agricultural marketplace, biotech crops has steadily grown in acreage in the countries of the world Read More
Crop InputsBayer: 5 Reasons We Disagree With Maryland Neonic Ban
April 12, 2016
We’re disappointed that the Maryland legislature chose not to stand up for sound science and the rights of Maryland’s homeowners Read More
Corn
OpinionChallenging Global Economic Conditions Putting More Heat On U.S. Ag Retailers
April 7, 2016
There it is. That vague, slightly sickening feeling in the pit of my stomach. Things are getting weird out there. Read More
ScoutPro iPad
Precision AgWhat’s Trending In Soil Testing And Scouting
April 6, 2016
Keeping up on soil testing and scouting, especially following unusual weather conditions, can play a role in maximizing yields. Soil Read More
Latest News
BAICOR
CropLife 100BRANDT Acquires Utah Specialty Fertilizer Company
April 28, 2016
BRANDT, a leading agriculture retailer and manufacturer of specialty ag products, has acquired a majority interest in BAICOR, L.C. BAICOR, Read More
Soybean field
Industry NewsVerdesian Life Sciences Adds Vice President Of Business…
April 28, 2016
Verdesian Life Sciences has announced the addition of Marc Treurniet to the plant health and nutrition company’s management team. Treurniet Read More
ManagementBiotech Crops Developments and Millennials
April 28, 2016
Editors Eric Sfiligoj and Paul Schrimpf talk about the latest activities in biotech crops and a major shift in the Read More
Industry NewsNachurs-Alpine, Pathway Biologic Extend Marketing Agree…
April 28, 2016
Nachurs-Alpine Solutions (Marion, OH) and Pathway Biologic (Plant City, FL) announce an extension to their exclusive marketing agreement specific to Read More
MicronutrientsCharah Add Three Warehouses For SUL4R-PLUS Fertilizer
April 28, 2016
Charah, Inc., a total solutions company providing unparalleled service and innovation for the coal-fired power generation industry, announced today that Read More
Spenser Forgey, Yahama Fortix
FungicidesIndiana Farmer Wins Arysta LifeScience FORTIX Fungicide…
April 28, 2016
Arysta LifeScience North America recently presented Spenser Forgey, a grower from Young America, IN, with a new 2016 Yamaha Grizzly Read More
Corn Field
HerbicidesNew Wilbur‐Ellis Herbicide Targets Volunteer Corn
April 28, 2016
Wilbur‐Ellis Co., a recognized leader in marketing and distribution of crop protection products, as well as precision agriculture technology, has Read More
StewardshipNRCS To Help Farmers Measure Conservation Impacts On Wa…
April 27, 2016
The USDA has announced the availability of $2 million to help farmers install edge-of-field stations that monitor water quality as Read More
Planter in Iowa
EquipmentTop 10 Twitter Pics For #Plant16
April 27, 2016
Despite some wet weather in parts of the Midwest, growers and ag retailers are working feverishly to plant this year’s Read More
HerbicidesHELM AGRO Launches New HELM Sulfentrazone 4F Herbicide
April 26, 2016
HELM AGRO US, Inc. has announced the federal Section 3 registration of its new HELM Sulfentrazone 4F herbicide. Classified as a Read More
Valley Irrigation Valley 8000 series on corn
EquipmentValley Irrigation Receives Environmental Stewardship Ho…
April 26, 2016
Valley Irrigation has been recognized as a Groundwater Guardian Green Site by the Groundwater Foundation. The Groundwater Guardian Green Site Read More
Eric SfiligojMissing The Family Ties In Agriculture
April 25, 2016
By its nature, the agriculture market is cyclical. Up and down cycles come and go with a regular pattern. For Read More
HerbicidesHerbicide Resistance In Waterhemp Continues To Grow
April 22, 2016
Twenty-five years ago, waterhemp was virtually unknown to Illinois farmers. Today, the broadleaf weed blankets corn and soybean fields across Read More
ManagementIllinois Leads The Nation In 4R Certified Nutrient Mana…
April 22, 2016
As Illinois agriculture works to educate farmers about minimizing environmental impact and optimizing the use of ag nutrients, Illinois now leads Read More
Social media
Matt Hopkins7 Social Media Trends Shaping Ag Retail In 2016
April 22, 2016
After writing my last column on why social media is a must for ag retailers, I heard from several readers Read More
Industry NewsArysta LifeScience Adds Corey Abels To Midwest Sales Te…
April 22, 2016
Arysta LifeScience North America recently announced the addition of Corey Abels as Territory Sales Manager for the Midwest region. In Read More
Soybean Field
HerbicidesHELM AGRO US Unveils New Sheridan 25 WG Herbicide
April 22, 2016
HELM AGRO US, Inc. has announced the federal Section 3 registration of its new Sheridan 25 WG herbicide for selective Read More
ManagementCentennial’s Jim Fargo Talks Ag Retail
April 21, 2016
Special guest Jim Fargo discusses challenges facing this CropLife 100 retailer. Read More