Palmer Amaranth Recommendations For 2014 Growing Season

Palmer amaranth is a weed species that must be thoughtfully and carefully managed. Simply attempting to control Palmer amaranth often leads to ineffective herbicide applications, substantial crop yield loss, and increased weed infestations, said University of Illinois weed sciences researcher Aaron Hager.

“If ignored or otherwise not effectively managed, Palmer amaranth can reduce corn and soybean yield to nearly zero,” Hager said. “The threat of Palmer amaranth during the 2014 growing season is very real across a large portion of Illinois.”

The University of Illinois weed science program has developed recommendations for management of Palmer amaranth in agronomic crops. These recommendations were developed in accordance with the unique growth characteristics of this weed species. The goals of the recommendations are two-fold: to reduce the potential for Palmer amaranth to negatively impact crop yield, and to reduce Palmer amaranth seed production, which ultimately augments the soil seed bank and perpetuates the species.

Three general principles of Palmer amaranth management include:

• Prevention is preferable to eradication. Prevention refers to utilizing tactics that prevent weed seed introduction and weed seed production.

“Palmer amaranth is not native to Illinois so any population discovered in the state originated from seed that somehow was moved into the state,” Hager said. “The myriad of ways in which Palmer amaranth seeds can be transported, however, makes preventing seed introduction extremely challenging. Once Palmer amaranth populations become established, utilizing any and all tactics to prevent seed production becomes of paramount importance.”

• It is not uncommon for annual herbicide costs to at least double once Palmer amaranth becomes established. There are simply no soil- or foliar-applied herbicides that will provide sufficient control of Palmer amaranth throughout the entire growing season.

• Control of Palmer amaranth should not be less than 100%.

“In other words, the threshold for this invasive and extremely competitive species is zero,” the researcher said. “Female Palmer amaranth plants produce tremendous amounts of seed, and in less than five years a few surviving plants can produce enough seed to completely shift the weed spectrum in any particular field.”

Recommendations based on Palmer amaranth germination and emergence characteristics include:

• Be certain to control all emerged Palmer amaranth plants before planting corn or soybean. Burn-down herbicides or thorough tillage are effective tactics to control emerged Palmer amaranth plants before planting. Keep in mind, however, that glyphosate will not control glyphosate-resistant Palmer amaranth and that growth regulator herbicides (such as 2,4-D or dicamba) are most effective on Palmer amaranth plants less than 4 inches tall. If pre-plant scouting (which is especially important prior to planting soybean) reveals Palmer amaranth plants taller than 4 inches, consider using tillage instead of herbicides to control the plants.

• Apply a full rate (based on label recommendations for soil texture and organic matter content) of an effective soil residual herbicide no sooner than seven days prior to planting and no more than three days after planting. Many soil residual herbicides that are effective for controlling waterhemp are also effective for controlling Palmer amaranth. In soybeans, products containing sulfentrazone (Authority) or flumioxazin (Valor) have provided effective control of Palmer amaranth. Application rates of products containing these active ingredients should provide a minimum of 0.25 lb ai/acre sulfentrazone or 0.063-0.095 lb ai/acre flumioxazin.

Hager said growers should not rely solely on glyphosate to control Palmer amaranth. “Molecular assays have indicated that resistance to glyphosate appears to be relatively common among recently identified Palmer amaranth populations in Illinois,” he explained.

Recommendations based on Palmer amaranth growth rate include:

• Begin scouting fields within 14 to 21 days after crop emergence. “We recommend this interval even for fields previously treated with a soil residual herbicide applied close to planting,” he explained.

• Foliar-applied herbicides must be applied before Palmer amaranth plants exceed 4 inches in height. The effectiveness of most foliar-applied herbicides dramatically decreases when Palmer amaranth plants are taller than 4 inches. Postemergence herbicides that demonstrate control or suppression of Palmer amaranth include synthetic auxin herbicides (dicamba, 2,4-D), diphenylethers (acifluorfen, lactofen, fomesafen), glufosinate, glyphosate, and HPPD inhibitors (mesotrione, tembotrione, topramezone).

• Consider including a soil residual herbicide during the application of the foliar-applied herbicide. A soil residual herbicide applied with the foliar-applied herbicide can help control additional Palmer amaranth emergence and allow the crop to gain a competitive advantage over later-emerging weeds.

• Fields should be scouted 7 to 14 days after application of the foliar-applied herbicide to determine herbicide effectiveness; if the soil residual herbicide included with the post application is providing effective control; and if additional Palmer amaranth plants have emerged.

“If scouting reveals additional Palmer amaranth plants have emerged, make a second application of a foliar-applied herbicide before Palmer amaranth plants are 4 inches tall,” Hager said.

In regard to Palmer amaranth seed production, Hager said research has demonstrated that female Palmer amaranth plants are capable of producing numbers of seed comparable to that of waterhemp (several hundred thousand to over one million). “Physically remove any remaining Palmer amaranth plants before the plants reach the reproductive growth stage. Plants should be severed at or below the soil surface and carried out of the field. Severed plants can root at the stem if left on the soil surface, and plants can regenerate from stems severed above the soil surface,” he said.

Source: Illinois Ag Connection

Topics:

Leave a Reply

Crop Inputs Stories

MicronutrientsMicronutrients Going Macro
September 9, 2014
Between 2014’s fantastic growing conditions and a heightened awareness on plant nutrition, the major players in micronutrients are gearing up for another big year. Read More
FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
FungicidesSudden Death Syndrome, Brown Stem Rot Reported In Indiana Soybeans
September 3, 2014
Farmers and retailers should be watching for symptoms of these two diseases over the next few weeks as they are best managed through preventative methods. Read More
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

Trending Articles

FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
CropLife 100CHS To Build $3 Billion Fertilizer Plant In North Dakota
September 5, 2014
The fertilizer plant in Spiritwood will be the single largest investment in CHS history, as well as the single largest private investment project ever undertaken in North Dakota. Read More
EquipmentNew Holland Acquires Miller-St. Nazianz
September 3, 2014
The assets of Miller acquired as part of the transaction will become part of New Holland Agriculture, a CNH Industrial brand, building on a successful four-year partnership between the two companies. Read More
CropLife 100Pinnacle Acquires East Kansas Chemical
September 2, 2014
Ranked 82nd on the CropLife 100, East Kansas Chemical will operate as part of Pinnacle's Performance Agriculture brand. Read More
MAGIE 2014 ShowStopper
EquipmentJohn Deere Again Wins MAGIE ShowStopper Award
August 25, 2014
For the second consecutive year, John Deere was honored at the Midwest AG Industries Exposition (MAGIE) for its new R4045 sprayer. Read More
ManagementExpert To Discuss Farmland Value, Rent At Farm Science Review
August 18, 2014
While cropland values in Ohio increased in the past two years, they have remained flat in 2014, declining in some cases, according to an Ohio State University agricultural economist. Read More

Latest News

Equipment2014 Product Of The Year Voting
September 19, 2014
Many new products were introduced to the ag retail marketplace this year. From this group, CropLife IRON and its consulting partners have selected five finalists for the Product of the Year award. Please cast your vote today to help us determine the winner. Read More
Equipment2014 Farm Science Review Crowd Tops 2013 Show
September 19, 2014
The 52nd annual Ohio State University Farm Science Review welcomed more than 130,000 farmers, industry professionals, FFA students and agricultural enthusiasts during the three-day event. Read More
Seed/BiotechUSDA Approves Enlist Following Rigorous Review
September 18, 2014
Dow AgroSciences now awaits EPA registration of Enlist Duo herbicide, the companion herbicide to the Enlist traits, which is expected in the near future. Read More
BlendersYargus Appoints New Plant Manager
September 18, 2014
Steve Shaffer will direct and coordinate daily operations at the company’s Marshall, IL, manufacturing plant, where the Layco line of material handling equipment is produced. Read More
CropLife 100Pinnacle Acquires Kansas-Based Cedar Ridge Supply
September 16, 2014
Cedar Ridge Supply will operate as part of Pinnacle's Performance Agriculture brand. Read More
StewardshipSecretary Vilsack Highlights Innovative Conservation Ef…
September 15, 2014
Nearly $16 million in Conservation Innovation Grants (CIGs) will be awarded to 47 organizations to help develop cutting-edge ideas to accelerate innovation in private lands conservation. Read More
Seed/BiotechSyngenta Responds To Cargill Lawsuit
September 15, 2014
Syngenta believes that the lawsuit is without merit and strongly upholds the right of growers to have access to approved new technologies. Read More
Equipment2014 Farm Science Review Launches Mobile App
September 15, 2014
Smartphone and tablet users planning on attending the 2014 Farm Science Review can now download this year’s customized mobile application. Read More
CropLife 100Southern States Coop Grower Sets Georgia Soybean Yield …
September 15, 2014
Georgia farmer Randy Dowdy's soybeans yielded an astonishing 110.66 bushels per acre, crushing the previous record of 82 bushels-per-acre. Read More
NIMITZ Treated vs Untreated pepper plant
InsecticidesNIMITZ Nematicide Approved By EPA
September 12, 2014
NIMITZ is a novel, non-fumigant nematicide with simplified application features, user safety and an active ingredient with a unique mode of action. Read More
InsecticidesMarrone Bio Innovations Receives Patent For Chromobacte…
September 11, 2014
The patent is the first step for MBI in developing a commercially viable product to inhibit infestations of corn rootworm larvae across America and other regions. Read More
HerbicidesDow AgroSciences: Keeping The Pipeline Stocked
September 11, 2014
Dow AgroSciences is embracing product diversity to drive the company’s future. Read More
CropLife 100CHS Is Official Partner Of New St. Paul Ballpark
September 10, 2014
The new ballpark in St. Paul, MN, officially became CHS Field with Twin Cities-based CHS Inc. revealed as the naming rights partner. Read More
EquipmentHagie Honors Farming Stewardship Leaders
September 10, 2014
The Iowa Farm Environmental Leader award recognizes Iowa farmers as environmental leaders that are committed to healthy soils and improved water quality. Read More
Precision AgPlantBeat: Your Plants’ Pulse In The Palm Of Your Han…
September 10, 2014
A new agronomic monitoring and recommendation service from Phytech could rewrite the book on real-time plant health status monitoring. Read More
StewardshipCCAs Making Headway With 4R Program In Lake Erie Wester…
September 9, 2014
Certified Crop Advisers are implementing the 4R Nutrient Stewardship Certification program in Lake Erie's Western Basin to improve water quality. Read More
MicronutrientsMicronutrients Going Macro
September 9, 2014
Between 2014’s fantastic growing conditions and a heightened awareness on plant nutrition, the major players in micronutrients are gearing up for another big year. Read More
Crop InputsFMC Announces Cheminova Takeover
September 8, 2014
FMC Corporation today announced that it has signed a definitive agreement to acquire Cheminova, a wholly owned subsidiary of Auriga Industries. Read More