When Weed Control Goes Wrong

Beyond the possibility of resistance developing, ineffective control exacts cost to growers in lost yield.

Quantifying the losses that poor weed control can cause grower customers is no simple matter. Shane Eck, location manager at Mid Kansas Cooperative (MKC), Lindsborg, KS, says measuring losses quantitatively due to the weeds “could be tough without doing a side-by-side comparison.”

Fortunately, many researchers have taken on that “hard numbers” question.

Mark Rosenberg, Extension agronomy/weeds field specialist, South Dakota State University (SDSU) reports on one sobering test his team did: Even though glyphosate was applied two to three weeks after corn and weed emergence in high weed density plots, yield losses measured as much as 20 to 40 bushels per acre.

Mature Waterhemp in Corn
Studies show that weeds can reduce corn yields by about 1% per day starting about one week after corn/weed emergence. Pictured is mature waterhemp in corn.

SDSU specialists commonly suggest growers control weeds within three to five weeks after crop emergence to prevent lasting impacts on corn growth and yield. They also recommend preemergence herbicides to minimize yield loss as well as minimize selection for glyphosate resistant weeds.

Rosenberg says preemergence products can also help soybeans, “but mostly for the benefits of increasing the consistency of weed control, managing glyphosate resistant weeds, and increasing flexibility in the timing of post-emergence application.”

Growers can actually identify the most competitive weeds in corn: they’ll be three to four inches tall when corn reaches the V-3 to V-4 growth stage. Research at Iowa State University has shown these competitive weeds can reduce yields by about three bushels per acre for every day they are left uncontrolled. Rosenberg says SDSU studies proved these weeds can reduce corn yields by approximately 1% per day starting at about one week after corn/weed emergence. Bottom line: If these weeds are controlled early, crops will develop the vigor to compete with later emerging weeds.

Application Timing Science

Weeds may do even more than compete with crops for valuable resources. According to work reported by Bob Hartzler, Extension weed management specialist, Iowa State University, a corn plant can actually detect weeds in its vicinity by detecting changes in light quality when sunlight is reflected off of the weeds. The corn then reallocates its resources to grow taller to reduce the chance of the weed intercepting sunlight the corn wants. The phenomenon is called shade avoidance. Such resource re-channeling has a negative impact on future crop growth.

In fact, research in Canada found that corn growing with weeds was affected by the shade response as early as three days after emergence — with its highest sensitivity to the shade issue in the first week after emergence.

Hartzler has found determining that moment when weeds first cause yield loss — the “critical period” — can be complex because of the number of factors involved: weed species, number of weeds, emergence date; cropping practices including cultivar, row spacing, population, tillage and environment. He says the critical period may occur as early as two weeks or as late as 10 weeks or later after planting.

In its resources, the Weed Science Society of America (WSSA) points out that poor weed control has consequences beyond yield losses, including reduced commodity prices because of weed-seed contamination, reduced land values, costs of mechanical and cultural controls, and ultimately the additional expense of alternative herbicides or cropping systems — or both — for managing resistant weeds.

WSSA has published findings by several weed scientists, gathered over the last eight years:

  • Cases of glyphosate resistant horseweed have resulted in a net increase in production costs of just over $70 per acre in Tennessee soybeans.
  • Cases of glyphosate resistant common waterhemp have increased production costs by about $118 per acre in Missouri soybeans.

Similarly, cases of glyphosate resistant Palmer amaranth have added approximately $118 per acre in weed management costs in Georgia and Arkansas cotton production systems.

  • Cases of propanil- and quinclorac-resistant barnyardgrass have added additional costs totaling approximately $158 per acre in Arkansas rice.

From The Field

Dealers we talked with have seen yield losses in clients’ fields. When asked how bad resistance is in his territory, Jeff Consbruck, seed lead, CPI Coop, Hastings, NE, said over the past couple of years he’s seen some yield being impacted from weeds that treatments could not knock down. While CPI hasn’t seen extensive losses so far, “if we don’t get on top of this soon, we will have horror stories to tell,” he says.

Getting on top of the issue takes a commitment not all growers are willing to make. Kevin Mainord, sales and marketing director with MRM Ag Services, East Prairie, MO, estimates that about 80% of customers are adapting to new practices needed to deal with resistance — Roundup is not controlling the spectrum of weeds it used to. But 20% are not willing to go into the complexities and costs of multiple product applications.

One service MRM’s customers can purchase is scouting for both weed and insect issues. The investment offers two-for-the-price-of-one benefits.

Mainord says timing herbicide applications for optimum kill is critical. If weather becomes a problem and delays ground spraying at key windows, his company can go into a customer’s fields with aerial applications because the firm operates its own plane. Managing weeds this way adds cost, but the yield saved may be worth it.

Topics:

Leave a Reply

Weed Resistance Stories

Weed ResistanceWeeds: The Fearsome Five
October 1, 2013
Although there are currently dozens of weeds that show some kind of resistance to herbicides, these five are the most troublesome. Read More
Weed ResistanceWeed Management Program Profiles
October 1, 2013
Here’s quick look at weed control strategies and their cost. Read More
Weed ResistanceRecognizing Resistance
October 1, 2013
Recognizing the presence of herbicide-resistant weeds and formulating a total management plan is becoming more important than ever. Read More
Weed ResistanceOptimizing Applications
October 1, 2013
Sophisticated tank mixes, multiple adjuvants and surfactants — this is the future of herbicide application. Read More
Top 100 Articles
CropLife 100Southern States Coop Hosting Drone Flight This Friday
August 3, 2015
Southern States Cooperative — No. 9 on the CropLife 100 — is hosting an FAA-approved drone demonstration at Grandview Farms Read More
CropLife 100Allied Ag Distributors Adds Four New Owners
July 30, 2015
Aligned Ag Distributors LLC has announced the addition of four new customer/owners to Franklin Holding Co. LLC. They are: The Read More
CropLife 100Pinnacle Purchases California-Based Specialty Crops Retailer
July 20, 2015
Pinnacle Agriculture Holdings has successfully acquired California-based NH3 Service Co.  Operating as part of Pinnacle’s Performance Agriculture brand, the new locations Read More
Asmus Farm Supply liquid fertilizer facility features 20,000 square feet
CropLife 100Slideshow: Asmus Farm Supply Shows Off Its New Liquid Fertilizer Facility
July 15, 2015
Asmus Farm Supply, Rake, IA, recently added a new liquid fertilizer facility to its company operations. The new liquid fertilizer Read More
CropLife 100Wilbur-Ellis Feed Division Facilities Receive Safe Feed/Safe Food Certification
July 13, 2015
Wilbur-Ellis Co.’s Feed Division, a marketer and distributor of value-added feed ingredients for the aquaculture, livestock and pet food industries Read More
CropLife 100BRANDT Expands To Brazil With Acquisition
July 8, 2015
BRANDT has acquired a majority interest in Target Brasil Fertilizantes Ltda. through its Brazilian subsidiary. Target Brasil manufactures, distributes and Read More
Latest News
StewardshipOhio Grower: Why Water Quality Matters To Me
August 3, 2015
Fresh off the first anniversary of last summer’s unfortunate Toledo Water Crisis — which was largely attributed in mainstream media Read More
Young soybean field
Industry NewsH.J. Baker To Build New Facility In Emporia, KS
August 3, 2015
H.J. Baker has announced the expansion of its Animal Health and Nutrition division with the ground breaking of a new Read More
Young corn plants
Crop InputsNufarm Reorganizing Ag, Industrial Vegetation Managemen…
August 3, 2015
Today Nufarm announced a reorganization of its Agriculture and Industrial Vegetation Management sales and marketing organizations effective August 1, 2015. Read More
StewardshipExcellence Through Stewardship Reaches 30 Members
August 3, 2015
Excellence Through Stewardship, a non-profit that promotes the adoption of best practices and stewardship in agricultural technology, reached the milestone Read More
CropLife 100Southern States Coop Hosting Drone Flight This Friday
August 3, 2015
Southern States Cooperative — No. 9 on the CropLife 100 — is hosting an FAA-approved drone demonstration at Grandview Farms Read More
CropLife 100Allied Ag Distributors Adds Four New Owners
July 30, 2015
Aligned Ag Distributors LLC has announced the addition of four new customer/owners to Franklin Holding Co. LLC. They are: The Read More
FungicidesReport: Sudden Death Syndrome Symptoms Appearing In Soy…
July 30, 2015
Last week, symptoms of sudden death syndrome (SDS) began to appear in April 15-planted soybeans at the University of Illinois’s Read More
Seed/BiotechAdvanta Seeds Adds New Phoenix Corn Hybrids
July 30, 2015
Corn growers in the High Plains and Western states have new options available for the 2016 growing season from Advanta Read More
ManagementTechnology and agriculture: a Futurist’s Perspective
July 30, 2015
Futurist David Zach, speaking at this week’s InfoAg Conference in St. Louis, shared thoughts on the benefits and limitations of Read More
Biofuels Plant in Lousiana
Industry NewsIdle Biofuels Plant In Louisiana To Reopen As Ammonia F…
July 30, 2015
A Lithuania-based company plans to spend $265 million to reopen an idle biofuels refinery in Grant Parish as an ammonia Read More
FFA at Monsanto Booth at the 2015 National Farm Machinery Show
Industry NewsFive Students Receive The 2015 Monty’s Plant Food Compa…
July 29, 2015
This fall, five college-bound students will have financial support through the Monty’s Plant Food Company FFA Scholarship. All five scholarship Read More
GYPSOIL Blendable Pellets
Crop InputsBeneficial Reuse Management Launches Pelletized Gypsum …
July 29, 2015
Beneficial Reuse Management (BRM) announced this week at Ag Media Summit that its GYPSOIL Pelletized Products Division will open a Read More
StewardshipOhio Water Quality Project To Determine How Much Phosph…
July 27, 2015
Researchers with the College of Food, Agricultural, and Environmental Sciences at The Ohio State University are looking for farmers in Read More
FertilizerKoch Agronomic Services Launches N-TEGRATION Technology
July 27, 2015
Koch Agronomic Services, LLC (KAS) has launched  N-TEGRATION Technology, a process technology platform designed to enable production of enhanced efficiency fertilizers at Read More
HerbicidesExpert: IARC Herbicide Classifications Leading To Confu…
July 24, 2015
Few people in the crop protection industry had heard of the International Agency for Research on Cancer (IARC) before this Read More
ManagementFCI Trade Summit Update & Precision Tank Turns 50
July 23, 2015
Editors Dave Frabotta and Eric Sfiligoj discuss the upcoming FCI Trade Summit in Las Vegas, NV, and how Precision Tank Read More
Palmer pigweed seedhead in cotton
HerbicidesUSDA Deregulates Dow AgroSciences’ Enlist Cotton Trait
July 23, 2015
The USDA today issued its decision deregulating Dow AgroSciences’ Enlist cotton trait in the U.S. The USDA has now completed its Read More
Industry NewsVerdesian Life Sciences Showcases Versatile Product Por…
July 23, 2015
Technology has revolutionized agriculture by bringing farmers, retailers and distributors to the forefront of the digital age. To meet the Read More