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

HerbicidesScouting Key To Next Season’s Soybean Herbicide Program
August 12, 2014
When growing soybeans, growers need to think ahead to stay one step ahead of weeds. That means examining weed threats and evaluating which herbicides work best. Read More
HerbicidesArysta Touts Burndown Herbicide For Brome Management In Wheat
June 4, 2014
Arysta LifeScience North America recommends PRE-PARE Burndown Herbicide for effective brome management in winter wheat. Read More
HerbicidesFall Herbicide Applications More Effectively Manage Resistant Italian Ryegrass
May 14, 2014
Field studies show that a fall application of certain herbicides before weed emergence, leads to more successful crop planting and weed control in spring. Read More
Waterhemp in soybean stubble
HerbicidesThe Weed Resistance Problem: A Matter Of Billions
April 1, 2014
Not only is the amount of money being spent to control these yield robbers high, but the toll it has taken on the human population is growing lager by the day. Read More

Top 100 Articles

CropLife 100CHS: Driving Momentum To Help Farmer-Owners Grow
December 11, 2014
CHS Inc., the nation’s leading farmer-owned cooperative and a global energy, grains and foods company, must capture new opportunities to Read More
CropLife 100BRANDT, Verdesian Ink Distribution Agreement
December 9, 2014
The agreement grants BRANDT the exclusive right to sell and market Verdesian’s patented Steric chemistry in the Turf and Ornamental and eastern U.S. ag markets under the BRANDT Reaction product line name. Read More
CropLife 100CropLife 100: The Colors Of Custom Application
December 5, 2014
Although many color spray rigs are in the yards of the nation’s top ag retailers, the majority of them still come in only a few shades. Read More
CropLife 100Pinnacle Invests In Meridian Agriculture Distribution
December 4, 2014
Meridian will provide retailers with supplier-branded products and numerous opportunities to differentiate themselves from their competitors. Read More
CropLife 100CropLife 100: Entering A New Seed Era
December 4, 2014
The seed category has been re-vitalized during the past few years, and more good news (and varieties) are headed the industry’s way in 2015. Read More
CropLife 100CropLife 100: The Depressed State Of Fertilizer
December 3, 2014
Following downright giddy growth earlier this decade, fertilizer sales have fallen back down to earth the past two years. Read More

Latest News

Seed/BiotechKaren Arthur Joins AgriThority As Seed Treatment Produc…
December 19, 2014
Prior to joining AgriThority, Arthur directed research and development programs, overseeing laboratory and field research, to build the Valent U.S.A. seed treatment portfolio. Read More
EquipmentJohn Deere To Sell Crop Insurance Business
December 19, 2014
Deere & Co. has reached a definitive agreement to sell its crop insurance business, subject to regulatory approval, to Farmers Mutual Hail Insurance Co. of Iowa. Read More
Crop InputsNufarm Fills Regulatory VP Position
December 18, 2014
Nufarm announced today that Rob Schwehr has been promoted to the position of Vice President of Innovation & Regulatory Affairs for Nufarm Americas. Read More
Seed/BiotechReport: China Approves Viptera Corn, U.S. Officials Awa…
December 17, 2014
Chinese authorities have informed some agriculture industry officials the government has approved U.S. imports of a type of genetically modified corn developed by Syngenta. Read More
FertilizerMonty’s Plant Food Brings In New Sales Rep
December 16, 2014
Monty's Plant Food Company has hired Warren Kearns as its newest Sales Representative for the South Carolina area. Read More
EquipmentHagie Wins 2014 CropLife IRON Product Of The Year Award
December 15, 2014
The self-propelled sprayer maker has a hit on its hands with the new STS Series model. Read More
Syngenta
Seed/BiotechSyngenta Sees China Approving Contentious GMO Corn Soon
December 15, 2014
Syngenta will make an announcement when it receives official documentation from China that Agrisure Viptera corn, known as MIR 162, has been cleared for import. Read More
Crop InputsVerdesian Life Sciences Names Vice President Of Communi…
December 15, 2014
Amy Bugg will oversee the execution of all promotional strategies for the corporate brand and the complete product portfolio. Read More
StewardshipFarmers, Retailers Attend 4R Certification 4U Workshop
December 15, 2014
More than 160 farmers and ag retailer attended the “4R Certification 4U” workshop December 12 to learn more about the 4Rs of nutrient stewardship, water quality research in the area and cost-sharing opportunities. Read More
Matt Hopkins10 Best New Agriculture Apps For 2015
December 15, 2014
These new agriculture apps are certain to help ag professionals do their jobs more efficiently in 2015 and beyond. Read More
ManagementARA Learnings, Retail Buying Intentions: Welcome To Cro…
December 12, 2014
This informal video program puts news and events effecting retailers into context, and features Editors Paul Schrimpf and Eric Sfiligoj. Read More
Seed/BiotechMonsanto Herbicide-Tolerant Technology Closer To Commer…
December 12, 2014
The final EIS moves Monsanto one step closer to the introduction of Bollgard II XtendFlex cotton and Roundup Ready 2 Xtend soybeans, paving the way to provide access to dicamba-tolerant soybeans and cotton. Read More
Seed/BiotechUSDA Issues Final Environmental Impact Statement On Her…
December 12, 2014
The USDA Animal and Plant Health Inspection Service (APHIS) is issuing a final environmental impact statement on varieties of cotton and soybeans that have been genetically engineered for resistance to several herbicides, including the one known as dicamba. Read More
CropLife 100CHS: Driving Momentum To Help Farmer-Owners Grow
December 11, 2014
CHS Inc., the nation’s leading farmer-owned cooperative and a global energy, grains and foods company, must capture new opportunities to Read More
LegislationARA Applauds CFATS Passage Prior To Holiday Adjournment
December 11, 2014
The streamlined bill provides a four-year authorization of the CFATS program and guidance to DHS on key issues of chemical facility security Read More
Seed/BiotechBayer CropScience’s ILeVO Approved By EPA
December 11, 2014
EPA has approved ILeVO, the only seed treatment that protects the root system against infections caused by the Sudden Death Syndrome fungus and has activity against dangerous nematodes. Read More
Biologicals in Emerging Markets Map.
Crop InputsBiocontrols Could Quadruple By 2025; Will Regulators Pl…
December 11, 2014
The European experience with GMOs offers caution — and a promise — for biologicals. Read More
Crop InputsBASF Donates $75,000 To Feeding America
December 10, 2014
The donation will support Feeding America’s National Produce Program, an initiative that helps with planning, transportation and logistics to ensure fresh produce deliveries to the 200 member food banks around the country. Read More