Time Application Of Postemergence Herbicides

Properly timing the application of postemergence herbicides is critical, said Aaron Hager, University of Illinois Extension weed specialist. Recent precipitation, coupled with warm temperatures, will result in rapid growth of emerged weeds and possible reductions in corn yield if weeds persist too long.

“Unfortunately, it’s not possible to accurately predict the specific day after planting or emergence when weed interference begins to reduce corn yield,” Hager said. “This interval is influenced by many factors, and can vary based upon the weed spectrum, density of certain species, available soil moisture, etc.”

Weed scientists generally suggest an interval, based either upon weed size (in inches) or days after crop/weed emergence, during which postemergence herbicides should be applied to avoid crop yield loss via weed interference. In corn it is often recommended to remove weeds before they exceed about 2 inches tall. The longer weeds are allowed to remain with the crop the greater the likelihood of crop yield loss, Hager said.

“It’s important to remember that the labels of most postemergence corn herbicides allow applications at various crop growth stages, but almost all product labels indicate a maximum growth stage beyond which broadcast applications should not be made, and a few even a state minimum growth stage before which applications should not be made,” he said.

These growth stages are usually indicated as a particular plant height or leaf stage or both. For product labels that indicate a specific corn height and growth state, Hager advises growers to follow the more restrictive of the two.

“Application restrictions exist for several reasons, but of particular importance is the increased likelihood of crop injury if applications are made outside a specified growth stage or range,” he said.

Corn plant height is commonly used on many herbicide labels, but plant height may not always provide an accurate indication of the plant’s true physiological maturity. Hager said determining plant height may seem relatively straightforward, but using different benchmarks for measurement can lead to different plant heights.

“Generally, corn plant height is determined by measuring from the soil surface to the arch of the uppermost leaf that is at least 50 percent emerged from the whorl,” he said. “Be sure to measure several plants in a given field and average the numbers. Plant height is obviously influenced by many factors, including genetics and the growing environment. Adverse environmental conditions, such as cool air/soil temperatures, hail, etc., can greatly retard plant height and result in corn plants that are physiologically older than their height suggests.”

Many agronomists agree that leaf number is a more accurate measurement of corn developmental stage. Counting leaves and counting leaf collars are the two primary techniques used. Leaf counting begins with the short first leaf (the one with a rounded tip) and ends with the leaf that is at least 40 to 50 percent emerged from the whorl.

Counting leaf collars also begins with the short first leaf, but includes only leaves with a visible collar (the light-colored band where the leaf joins the stem). Leaves in the whorl or those without a fully developed collar are not counted. The leaf collar method quite often stages a corn plant at one leaf less than the leaf counting method, he said.

(Source: Illinois Ag Connection)

Leave a Reply

One comment on “Time Application Of Postemergence Herbicides

  1. Yes I am just a small time truck patch farmer in which I grow produce for the public and the family's. I live near the Tenneesse River, I do grow sweet corn and feild corn. My problem is a lot of grass,because of ground moisture on one end,the lowest end holding moisture,but that end produces so much better corn,espically when the dry times come, but I have found that you can not use just grass killer I mix up for my other produce, like peas,tomatoes,potatoes,brocolie,onions,carrots,watermelons,i.e; so forth.What would you suggest. Thank You;Freddie

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 100The Andersons Starts Venture Capital Subsidiary
January 26, 2015
The Andersons has established Maumee Ventures, a venture capital subsidiary designed to foster promising innovations that strategically align with the company’s core businesses. Read More
CropLife 100CHS Partners With Northern Partners Coop On Fertilizer Warehouse
January 21, 2015
In addition, the two companies will form a joint venture to build and operate a grain barge loading facility that will handle corn, soybeans and wheat for export through the CHS terminal at Myrtle Grove, LA. Read More
CropLife 100Wilbur-Ellis Move To Colorado Complete
January 20, 2015
Wilbur-Ellis Co. announces the opening of its new Agribusiness Division location in the Denver, CO, Metro Area. The new facility will host key personnel as the company shifts the base of its Agribusiness operations from California to Colorado. Read More
CropLife 100United Suppliers, McGregor Co., Five Others To Form Aligned Ag Distributors
January 20, 2015
These companies will continue to operate as independently owned and operated businesses, however, their crop protection divisions will now be formally aligned under the umbrella of Aligned Ag Distributors. Read More
CropLife 100Bozeman Named SEEDWAY Chief Operating Officer
January 16, 2015
He succeeds Donald Wertman, who will retire at the end of August 2015 after 40 years with the GROWMARK subsidiary. Read More
CropLife 100Wilbur-Ellis’ Craig Bair Honored For Safety Contributions To Ag Aviation
January 14, 2015
The William O. Marsh Safety Award recognizes significant achievements in safety, safety education or an outstanding operational safety program. Read More
Latest News
CropLife 100The Andersons Starts Venture Capital Subsidiary
January 26, 2015
The Andersons has established Maumee Ventures, a venture capital subsidiary designed to foster promising innovations that strategically align with the company’s core businesses. Read More
Exclusive state-of-the art Stueve Construction designed “Vista View” Elevated Control Room.
Eric Sfiligoj2015 Agricultural Market Read: Mixed
January 26, 2015
The agricultural market could look radically different this year, profit-wise, depending upon which segment you do business in. Read More
Edward Chell Biosafe
Crop InputsBioSafe Systems Names Ed Chell California Territory Man…
January 26, 2015
BioSafe Systems has announced the recent addition of Ed Chell as California Territory Manager for the agrichemical division, supporting the crop protection, water treatment and food safety business segments. Read More
InsecticidesBayer CropScience Introduces Sivanto Insecticide
January 26, 2015
Sivanto precisely targets key damaging pests at multiple insect life stages to prevent damage to plants and help minimize the spread of diseases from insect carriers. Read More
ManagementRetail Collaboration, Communicating Agriculture’s Good …
January 23, 2015
Editors Paul Schrimpf and Eric Sfiligoj discuss the recent creation of Aligned Ag Distributors, and the US Farmers and Ranchers Read More
FertilizerOSU Expert: Toledo Water Crisis A Turning Point For Ohi…
January 23, 2015
The August 2014 water crisis in Toledo, OH, impacted Ohioans’ views of Lake Erie algae problems by increasing the attribution of blame of algae growth on agriculture. Read More
FertilizerH.J. Baker Launching TIGER XP
January 22, 2015
Tiger-Sul introduces this next generation sulphur-bentonite product with a proprietary activator – ensuring farmers have a well-balanced nutrient replacement program. Read More
Crop InputsH.J. Baker Expands China Sales Force
January 21, 2015
Global Agricultural firm H.J. Baker announced that sales veteran Shi Dongshen has joined their Shanghai office in China. This newest hire follows the recent opening of their Lianyungang Sulphur Bentonite Plant. Read More
CropLife 100CHS Partners With Northern Partners Coop On Fertilizer …
January 21, 2015
In addition, the two companies will form a joint venture to build and operate a grain barge loading facility that will handle corn, soybeans and wheat for export through the CHS terminal at Myrtle Grove, LA. Read More
Matt Hopkins5 Bold Predictions For Ag Retail In 2015
January 21, 2015
This past year was filled with ups and downs for the nation’s top ag retailers, but what will 2015 have in store? Read More
SoftwareDeere Launches App Center
January 20, 2015
The John Deere App Center provides users the ability to search and find apps most useful to their business or operations. Read More
Crop InputsNew Syngenta Herbicide Approved In Soybeans, Sunflowers
January 20, 2015
Syngenta will sell BroadAxe XC herbicide in 2015 for use on soybeans, sunflowers and dry peas Read More
CropLife 100Wilbur-Ellis Move To Colorado Complete
January 20, 2015
Wilbur-Ellis Co. announces the opening of its new Agribusiness Division location in the Denver, CO, Metro Area. The new facility will host key personnel as the company shifts the base of its Agribusiness operations from California to Colorado. Read More
Crop InputsNovozymes Sales Figures Up For 2014
January 20, 2015
Novozymes announces its sales growth in 2014 was in line with expectations as sales grew by 7% compared with 2013. Read More
CropLife 100United Suppliers, McGregor Co., Five Others To Form Ali…
January 20, 2015
These companies will continue to operate as independently owned and operated businesses, however, their crop protection divisions will now be formally aligned under the umbrella of Aligned Ag Distributors. Read More
Eric SfiligojGMO Or DNA? LOL Or WTF?
January 19, 2015
A new survey finds the American public seems generally confused when it comes to any three-letter descriptor for their food. Read More
FertilizerAGROTAIN Wins No-Till Product Of The Year Again
January 19, 2015
This marks the 10th straight year AGROTAIN nitrogen stabilizer has been named the top product in this category; no other product has matched this honor Read More
FertilizerTFI President To Give Update On Nutrient Management Eff…
January 19, 2015
The Fertilizer Institute President Chris Jahn will give the keynote address at the 2015 Ohio AgriBusiness Association Industry Conference February 4. Read More