Weed Control In Sunflower - National Sunflower … across the country are accus-tomed to the...

THE SUNFLOWER / Weed Control Supplement / February 2010 1w

Weed Control In Sunflower

Special SupplementTo The Sunflower

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2w

Storms & Stewardship . . . . . . . . . . . . . . . . . . . . 4w

Spartan: The Workhorse Herbicide . . . . . . . . . . 6w

Palmer Amaranth Flexing Its Muscle . . . . . . . 10w

Other Soil-Incorporated Herbicides Still Needed 11w

What’s Available for ’10 . . . . . . . . . . . . . . . . . . 12w

Avoiding Crop Injury When UsingAssert for Mustard . . . . . . . . . . . . . . . . . . . 16w

— Introduction — Aweed is defined as a misplaced plant. Historically, sun-

flower producers have had to deal with many misplacedplants in their fields. That was especially true a decade or moreago, when there were only two or three herbicide choices.More choices exist today, and growers are using a combinationof herbicides and rotations to control troublesome weeds.

Not too long ago, sunflower growers depended on tillage fora large portion of their weed control. Since then reduced tillagehas become the norm, and the crop has moved further west intodrier areas where tillage isn’t as feasible. Preplant burndownand postemerge herbicides for grasses and broadleaves havedramatically changed the sunflower weed control landscape.

In this special supplement to The Sunflower, we discusssome of the most troublesome weeds, herbicide choices, someissues related to the most common products, and grower strate-gies for controlling weeds in today’s environment.

For the farmer, weed control is — after hybrid selection —likely the most critical production sunflower decision he makes.The National Sunflower Association has placed a great deal ofemphasis on new herbicide labels by partially financing the reg-istration costs of most of the products available today. It wouldbe great to have more herbicide choices. Unfortunately, thenumber of new herbicide introductions has been minimal dur-ing the past decade — and we’re not aware of anything in thenear-term pipeline that might fit sunflower.

Attaining a sunflower herbicide label is often accidental. Ifa new herbicide introduction doesn’t kill wild sunflower, thenthere is an opportunity for a potential sunflower label.Chemical companies do not generate herbicides specifically for

a smaller-acreage crop like sunflower, so this industry isdependent upon some luck that a product might fit.

Roundup Ready® is not a likely reality for sunflower. This ismainly due to the regulatory hurdles related to potential pollenoutcrossing to wild sunflower, a native plant in North America.

The National Sunflower Association has been conducting anintense fall field survey since 2002. Volunteers go into fieldsand assess production issues that may be impacting yields.Weed identification is a key category. Interestingly, the list ofmost troublesome weeds still finds kochia as the most commonspecies. Grasses are much less of a problem, due largely toexcellent postemergent herbicides. But other challenges — likeCanada thistle and palmer amaranth — face growers today.

What has changed is the intensity of the weed populations.No longer is it common to find a field literally covered withweeds. Now, weeds are usually found in field skips or openareas, or are randomly scattered in sections of the field. Theability to control weeds has had a significant impact on sun-flower yield enhancement. — Larry Kleingartner �

Most Commonly Found Weeds in Sunflower — 2002 & 2009

2002 2009North Dakota —1. Green foxtail Canada thistle2. Kochia Kochia

South Dakota —1. Kochia Redroot pigweed2. Green foxtail Kochia

Minnesota —1. Green foxtail Canada thistle2. Kochia Kochia

2002 2009Kansas —1. Puncture vine Palmer amaranth2. Volunteer grain Volunteer grain

Colorado —1. Russian thistle Russian thistle2. Kochia Puncture vine

Texas —1. Palmer amaranth Palmer amaranth2. Redroot pigweed Russian thistle

Source: National Sunflower Association Field Surveys

2w THE SUNFLOWER / Weed Control Supplement / February 2010

Growers across the country are accus-tomed to the uncertainty that comes

with all the variables in producing crops.The tough weather of 2009 drove thathome for sunflower growers in theUpper Midwest. Adding to the woes ofweather is the ever-present pressure fromtough weeds and diseases.

While no one can control the weath-er, there are ways to control the prob-lems of weeds and diseases. TheClearfield® Production System knocksback the biggest threats, but resistantweeds are beginning to emerge.Protecting this important technologythrough good stewardship practices willensure that resistant weeds and diseasesstay out of sunflower fields for growersacross the country.

‘Cold & Wet’ Creates Challenges

A late spring, cool summer and earlyfrost created a serious set of challengesfor Upper Midwest sunflower growersthis past season. From start to finish,many growers have been obliged to shifttheir practices to accommodate theforces of nature.

Dr. Kirk Howatt has been a weedresearcher in cereals and oilseed cropsat North Dakota State University for 10years. He counseled many growersstruggling with timing the regular func-tions of growing and harvesting sunflow-ers in 2009. “Even my own plots wereseven to 10 days late for planting this

year,” Howatt notes. “Developmentlagged behind all season.”

With pockets of frost hitting theregion after Labor Day, plants had nochance to dry down to the recommend-ed 30 to 35% moisture for preharvestherbicide application. Late-season treat-ments were tough to fit in because ofdelayed development and weather, thusincreasing disease and weed pressure.

“Diseases and weeds thrived afterinitial frosts, allowing continued inocu-lum and seed production,” Howatt says.“I had some growers [who] felt like theonly thing that really grew this year wasSclerotinia. . . . The lack of those end-of-season glyphosate treatments could leadto a bumper crop of spring weeds.”

The Clearfield Advantage

Howatt has been impressed with theimpact of the Clearfield ProductionSystem on sunflower in North Dakota.Clearfield plus a soil-applied componentcan manage early emerging weeds, mak-ing the window for postemergent appli-cations both broader and more flexible.

“With larger flushes of weeds like wemay well see in the coming year, theClearfield portfolio of products is a bighelp,” he observes. “Not only does itprovide good control of both broadleafweeds and grasses, but the control canbe achieved without losing marketabilityof nontransgenic varieties.”

Eastern North Dakota farmerAnthony Thilmony stopped growing sun-flower in the late 1990s and early 2000sbecause eastern black nightshade andmarsh elder clogged his fields, and hischoices for control were few and farbetween. With the introduction ofClearfield sunflower, Thilmony found asolution to his growing weed problem.

“When Clearfield sunflower [hybrids]were introduced, I tried them the firstyear and was totally impressed with con-trol of the two main weeds I’m worriedabout; and this allowed me to keep sun-flower in our rotation,” Thilmony says.

A Historic Discovery & Beyond

The introduction of Clearfield sun-flower provided growers with their firstopportunity to control most broadleafweeds with postemergent herbicideapplications. As part of the ClearfieldProduction System, BASF CropProtection introduced Beyond® herbi-cide, a member of the imidazolinonechemical family and an ALS inhibitor.

When Beyond herbicide is applied toClearfield sunflower at the two- to four-leaf stage, growers see both contact andresidual activity on broadleaf weeds andgrasses, including kochia, marsh elder,cocklebur, Canada thistle, foxtail, volun-teer cereals and non-Clearfield wild orvolunteer sunflower. Beyond is labeledfor use up to the eight-leaf stage, butperformance is best when applied at theearlier stage.

Beyond also works well in no-till set-tings, which may be increasingly impor-tant after delayed seasons like 2009.Applications of Beyond may help grow-ers get control of weeds and grasses thatwould otherwise survive because theywere not tilled under preplant.

Because it is a highly effective sys-tem for controlling a wide variety ofweeds, resistance to ALS inhibitorslooms large as a threat to crops.Researchers have already found popula-tions of kochia, pigweed, marsh elderand nightshade in North Dakota that areresistant to ALS inhibitors. To keep thisproblem from spreading, today’s growersmust practice technology stewardship toensure that the benefits of the ClearfieldProduction System are available for gen-erations to come.

Clearfield Sunflower Stewardship

If wild sunflower and other weedsbecome herbicide-tolerant, the effective-ness of these technologies for weed con-trol will diminish. That’s why growersusing the Clearfield Production Systemneed to be vigilant about responsible use

Ryan Bond and Chris Wharam, technicalmarket manager and technical servicerepresentative, respectively, for BASFCrop Protection, contributed informationfor this article.

Storms & StewardshipTough Weather & Even Tougher Weeds Increase Need for Clearfield Stewardship

If wild sunflower and otherweeds become herbicide-

tolerant, the effectiveness ofthese technologies will diminish.


of the products. Good stewardship prac-tices range from crop rotation to the useof non-ALS chemistries for herbicideresistance management.

The following are best practices forClearfield sunflower stewardship:

• Always grow Clearfield sunflowerin rotation with other non-Clearfieldcrops, such as wheat, corn or sunflower.Rotating crops breaks the cycle of con-tinuous sunflower production and allowsfor use of alternative mode-of-actionchemistries and different tillage options.

• Use alternative (non-ALS) mode-of-action herbicides such as a growthregulator or photosynthesis inhibitorwith activity on sunflower in the rota-tional crop. The alternative mode-of-action helps control volunteer Clearfieldsunflower and other ALS-resistant weeds.It also reduces the selection pressure ofALS-inhibiting herbicides from continu-ous dependence on the chemistry.

• Limit the sole reliance on ALS her-bicides to no more than two out of fouryears in the same field. Whenever pos-sible, use sequential herbicides or tank-mix partners with multiple modes-of-action on targeted weed species in thesunflower crop and in rotational crops.

• Do not plant Clearfield sunfloweron land with a history of heavy wildsunflower pressure. This helps reducethe threat of outcrossing Clearfield sun-flower with wild sunflower.

• Control emerged wild sunflower inthe field prior to planting Clearfield sun-flower by using non-ALS burndown her-bicides on no-till or minimum-till fields,or by tillage in conventional-till fields.Spraying glyphosate prior to plantingeliminates any wild sunflower in thearea that may be resistant to ALS-inhibit-ing herbicides, while also reducing thereliance on ALS herbicides in controllingwild sunflower.

• Spray a preplant or preemergenceherbicide earlier in the season, prior tospraying Beyond herbicide. A soil-applied grass herbicide like Prowl® H2Ocan be used before spraying Beyond toincrease weed control on targeted weedspecies and add another mode-of-actionto the sunflower program to help preventherbicide-tolerant weeds.

NDSU’s Kirk Howatt continues toevaluate Clearfield seed varieties

that will allow for improved control oftroublesome weeds with Beyond. Butuntil that time, he urges Clearfield sun-flower growers to incorporate steward-ship practices to keep weed populationslow and herbicide efficacy high.

“We can’t control the weather,”Howatt notes. “So we have to controlthe way we use the trait.” �

As when growing a Clearfield variety,sound stewardship also should be a

top priority for growers planting anExpressSun® sunflower variety in orderto avoid outcrossing to wild sunflowerand to preserve the system’s integrityand productivity.

The ExpressSun trait system incor-porates built-in tolerance to DuPont’sExpress® herbicide (with TotalSol™ sol-uble granules). As with Clearfield, theExpress-tolerance trait is incorporatedinto sunflower hybrids by traditionalplant breeding methods, so the hybridsare not considered to be “geneticallymodified.” Express is a member of thesulfonylurea family of herbicides.

DuPont and Pioneer Hi-BredInternational (which is owned byDuPont) offer the following stewardshipadvice regarding the use of ExpressSunhybrids:

• Always grow sunflower hybridswith the ExpressSun trait as part of amulti-year rotation with other crops.

— ExpressSun Varieties —

Croplan Genetics460 E,NSPioneer Hi-Bred InternationalP63N82P63ME70 P64HE01 (high oleic)Seeds 2000CobraFirebird

— Clearfield Varieties —

CHS SunflowerRoyal Hybrid 400 CL (confection)Croplan Genetics551 CL,NS 555 CL,DMR,NS564 CL,NSDahlgren & Company9530CL (confection)Legend SeedsLSF 223NCL

Mycogen Seeds8N270CLDM8N358CL8N358CLDM8N386CL8H288CLDM (high oleic)8H419CL (high oleic)8H419CLDM (high oleic)8H449CLDM (high oleic)Pannar Seeds8466 NS/CL8560 NS/CLProseedCL 7001CL 9001Red River Commodities2215 CL (confection)Seeds 2000Jaguar (confection)Badger CL (conoil)BarracudaBlazer CL ViperSyngenta Seeds3480 NS/CL/DM3980 NS/CL3880 CLTriumph Seeds680CL 6300 CL660CL859CL (high oleic)s870CL (high oleic)

• Use non-ALS/AHAS (non-group 2)mode-of-action herbicides in a tankmix with ALS/AHS herbicides — or as asequential treatment in the rotationalcrop — to control wild and volunteersunflower.

• Control wild sunflower in non-crop areas adjacent to ExpressSun traitsunflower fields through the use of non-ALS/AHAS herbicides and/or mowingprior to seedset.

• Use tillage to control emergedwild sunflower prior to planting hybridswith the ExpressSun trait, or by utilizingnon-ALS/AHAS burndown herbicides,or use ALS/AHAS burndown herbicidesin a tank mix with non-ALS/AHAS her-bicides to provide control of sunflower.

• As practical, use ALS/AHAS herbi-cides in a tank mix with non-ALS/AHASmode-of-action herbicides, or useALS/AHAS herbicides in a sequentialprogram that employs alternate modesof action to control wild and volunteersunflower. �

ExpressSun & Clearfield Hybrids for 2010

Good Stewardship Also Key with ExpressSun

Seed companies indicate the followingExpressSun and Clearfield sunflowerhybrids as available for 2010 planting.All are NuSun (mid-oleic) hybrids, exceptwhere otherwise noted. A “DM” or“DMR” designation indicates the hybridcarries resistance to downy mildew.


There was a great deal of celebrationwhen the first Section 18 label for

Spartan® (Sulfentrazone) was approvedin 1999 in multiple states. This was thefirst multi-spectrum broadleaf herbicideto be labeled for sunflower.

The need was great. Growers hadfew alternatives other than dinitroanilineherbicides like Treflan, Sonalan andProwl. Issues of weed resistance to thisherbicide family were popping up. Therewas an increasing interest in no-till, andproducing sunflower under that systemwas a real challenge prior to Spartan.

With few alternatives in the market,it didn’t take long for Spartan to go tothe top of the sunflower herbicide list.

The history of Spartan has not beenthe smoothest. Section 18 labels havealways been a challenge to acquire,especially in multiple states. In 2005the product’s manufacturer, FMC,

encountered a production issue thatshorted the market. There have beenperiodic crop damage and performanceissues. But most of that has beenworked out with research and fieldexperience. Overall, the product hasbeen a lifesaver for many sunflower pro-ducers. It is the most widely used sun-flower herbicide today.

The key weed of interest has alwaysbeen kochia. North Dakota State

University weed scientist Rich Zollinger,who did much of the early work on theproduct, happily reported to theNational Sunflower Association Board ofDirectors in 1998 that “Spartan literally‘smokes’ kochia.” That scenario contin-ues today, with excellent control ofkochia along with other small-seededbroadleaves.

Spartan was first available as a 75 DF

dry product. In 2005 it was changed toa liquid formulation, Spartan 4-F, for eas-ier mixing. Today, Spartan is teamed upwith other herbicides in a premix for fur-ther ease of handling. “Spartan Charge”is designed for the no-till producer. Thisformulation has added carfentrazone-ethyl (“Aim”) for faster preplant burn-down of small susceptible broadleafweeds such a ‘puffball’ kochia. “SpartanAdvance” has glyphosate added to theformulation for broad-spectrum preplantburndown for no-till and conventionalgrowers.

Use rates today are moderately lowerthan those during the early days of theproduct’s introduction, and mechanicalincorporation is not recommended.Also, the use of Spartan on soils withless than 1% organic matter has beenrestricted.

Minimizing Crop Damage Sam Lockhart, FMC technical sup-

port specialist, says FMC strongly advis-es growers to soil test to determineorganic matter, soil type and soil pH.This is critical for determining an appli-cation rate. “One rate does not fit everysoil type,” says Lockhart. Reducing ratesis necessary on soils with a pH of 7.0and greater, and on sandier and low-organic soils (often including hilltops).

Another area of concern is that grow-ers who use Spartan after plantingensure that they apply the product wellbefore seedlings begin to emerge andthat seed furrows are closed. Lockhartalso recommends that seeds be planted1.0 inch or deeper when using Spartanpostplant/preemerge. He advises grow-ers and certified crop advisors to closelyfollow the label-recommended ratesbased on soil types and other soil factorsdescribed above. He also advises usingvariable rate technology when possible.“It is usually the eroded hilltops thatresult in some seedling injury withoutdropping the rates in those areas of thefield,” Lockhart observes.

And if you do see seedling damage inparts of the field, like on hilltops?

Bruce Due, Northern Plains districtagronomist for Mycogen Seeds, says thatin most cases the plants grow out of theinjury and yield normally. “My experi-ence is that the plants will be stunted,


— Spartan —The Workhorse Herbicide

Below: Symptoms of Spartan injury to a young sunflower plant. “Sunflower usuallygrows out of any damage — except on very light soil with little to no organic mat-ter,” notes North Dakota State University extension weed specialist Rich Zollinger.“Under those conditions, injury may be permanent, with slight to heavy stand loss.This is why application rate by soil type is very important.” If there are wide fluc-tuations in soil type within a given field, Zollinger recommends using low rates ofSpartan in light soil and higher rates in finer-textured soils.

Despite Some Early Bumps in the Road, Versatile BroadleafProduct Has Become a Mainstay for Sunflower Producers

Pho

to:

Bru

ce D

ue FMC strongly advises growersto soil test to determine

organic matter, soil type andsoil pH before using Spartan.

but not behind in growth stages. Anuninjured eight-leaf plant may be sixinches tall, while an injured plant willstill be in the eight-leaf stage but per-haps only four inches tall,” Due states.

Rich Zollinger’s experience is thatsunflower usually grows out of any dam-age — but it depends on the rate andthe organic matter level. If the rate istoo high and the soil is very light withlittle or no organic matter, injury can bepermanent with a stand reduction.

FMC’s Lockhart agrees, saying thatthe injured plants usually grow out ofthe damage. The injured plant will bestunted and the leaves may be lighter incolor — somewhat variegated and withdark lesions.

The bottom line is that everyone isdoing a much better job of applying

the proper Spartan rates in concert withsoil types, and the damage issue hasbeen greatly minimized since the intro-duction of the product.

Spartan has proven itself in weedcontrol when timely rainfall occursresulting in good incorporation.National Sunflower Association volun-teers who participate in the annual sun-flower crop survey seldom see a fieldwith a kochia disaster. There may be afew plants here and there; but generallythis weed has been put on the backburner as far as impacting yield. It isstill the number one weed found in sun-flower fields in most states, but theintensity of the weed population is great-ly reduced when comparing it to thepre-Spartan days.

One of the major weeds in sunflowerfrom southern Nebraska to Texas isPalmer amaranth. Spartan does a goodjob of controlling the various pigweeds,including Palmer amaranth. Lockhartsays the key to controlling Palmer ama-ranth is moisture at planting for incorpo-ration. A rain event (or irrigation) of atleast 0.5 inch is critical for chemicalactivation. That is not always going tooccur in that region, where the growingseason is quite long and rain events canbe greatly extended.

Is there a place for Spartan as moreseed companies move their hybrids toeither a Clearfield® or ExpressSun® traitsystem? Lockhart says Spartan is a greatcompanion herbicide with Beyond- andExpress-resistant hybrids. Both Expressand Beyond are ALS herbicides, andALS-resistant kochia is best controlled bySpartan in sunflower. “It is really thebest way to control resistant kochia, andit is a great combined herbicide package— something that sunflower has reallynever had [before],” he concludes. —Larry Kleingartner �


Spartan Charge Use Rate Table (Sunflower)Fall, Preplant Burndown, Early Preplant & Preemergence

Broadcast Rate

% Organic Matter<1.5

1.5-3.0

>3

Fluid Ounces Spartan Charge / Acre— Soil Texture —

Coarse3.75 - 5.0

3.75 - 5.75

5.0 - 7.75

Medium3.75 - 5.75

5.0 - 7.75

5.75 - 8.5

Fine5.0 - 6.5

5.75 - 8.5

7.75 - 10.2

Use higher rates for soils of pH less than 7.0 & lowest rate for pH greater than 7.0 within the rate range.

Sou

rce:

Spa

rtan

Cha

rge

Labe

l

“This growing season, I’ll be looking at 600 new hybrids in our U.S. breeding program. The ultimate breeder’s goal is that 10% to 15% may eventually be advanced, finding

their way into your field—furthering the Pannar sunflower package of consistency, yield, and disease resistance.”

their way into you

Dawn GustafsonSunflower Researcher

Pannar Seed

“This growing

Powered byResearch

www.mycogen.com 1-800-MYCOGEN ®Mycogen and the Mycogen Logo are trademarks of Mycogen Corporation. ™“Science. Yield. Success.” is a trademark of Dow AgroSciences LLC. ®CLEARFIELD is a registered trademark of BASF Corporation.

™CruiserMaxx is a trademark of Syngenta Crop Protection Inc. ©2009 Mycogen Seeds. Mycogen Seeds is an affiliate of Dow AgroSciences LLC. S38-702-006 (8/09) BR 010-12425 MYCOSUNF9059

IT’S TIME TO MAKE ROOM FOR BIGGER PREMIUMS.

Science. Yield. Success.™

With the kind of premium potential

Mycogen® brand sunflowers deliver,

you’re going to need all the room

you can get. That’s because our

sunflowers deliver more oil per acre

and maximum profitability. It all starts with our portfolio. It’s the

largest one in the industry with six new hybrids to help give you

the widest range of sunflowers to choose from across all markets.

That means even more opportunities for higher premiums. And

because our hybrids come packed with innovative technologies

like genetic resistance to downy mildew, CLEARFIELD®

technology and CruiserMaxx™ sunflower treatment, these

sunflowers perform all season long. The end result is bigger

premiums — and ultimately, bigger pockets.

Let there be no doubt: Palmer ama-ranth has become an increasingly

“growing” weed problem in Kansas sun-flower fields.

If you question that statement, con-sider the results of the annual NationalSunflower Association crop survey. Thiscoordinated survey — conducted eachSeptember and encompassing severalkey sunflower states and the Canadianprovince of Manitoba — has foundPalmer amaranth to be the weed ofhighest incidence in Kansas sunflowerfields for the past five years.

In 2005, Palmer amaranth popula-tions were found in about 18% of thesurveyed Kansas fields, with the nextmost common weed, puncture vine,observed in 9% of the fields. The nextyear, 2006, the incidence level forPalmer amaranth exploded to 66% ofsurveyed Kansas fields, while that ofpuncture vine crept up to only about12%. The 2007 survey found Palmeramaranth in 88% of Kansas fields sur-veyed, with puncture vine jumping all

the way to 75%. The following year,2008, saw the Palmer amaranth inci-dence level climb to 92%, while punc-ture vine dropped to 64%. The 2009NSA crop survey found Palmer amaranthin 90% of the surveyed Kansas sun-flower fields, wile puncture vine wasnoted in just 20%.

Phil Stahlman is not the least bit sur-prised by these findings. “Palmer ama-ranth has become the most common ofall the pigweed species in the southernand central Great Plains,” says theKansas State University weed scientist.Stahlman, who is based at KSU’s HaysAgricultural Research Station, says he’sviewed Palmer amaranth plants flower-ing when just two inches tall. He’s alsoseen plants of this weed species growingto a seven- or eight-foot height.

Obviously aggressive, Palmer ama-ranth can be a serious competitor forsunflower, and numerous High Plainsgrowers can attest to its impact on seedyields. In one trial where Stahlmancompared hand-weeded plots to others

with heavy Palmer amaranth pressure,this weed’s presence slashed sunflowerseed yields by 54%.

Palmer amaranth also threatens acrop like sunflower because it germi-nates over an extended period of time.“Even in midsummer, if conditions areright,” Stahlman observes. It thus can bean issue for double-cropped sunflowerfields as well as full-season ones,although the weed pressure typically islower in second-crop ’flowers.

What are the sunflower grower’s bestoptions for controlling this increas-

ingly prolific weed?The program should begin in the

rotation’s preceding crops. “We proba-bly have the best success following aRoundup Ready® crop, simply becauseof the effectiveness of the [glyphosate] inthat crop,” Stahlman says. If followingwheat, as do a lot of Kansas ’flowers, afall burndown with glyphosate or anoth-er product will set the stage for goodcontrol in the next year’s sunflower.

In-season control of Palmer amaranthcan be achieved with Beyond® orExpress® if the sunflower hybrid beinggrown is a Clearfield® or ExpressSun®

variety. If, however, the Palmer ama-ranth population should have ALS resist-ance (as is the case in a number of fieldsthroughout Kansas), these products willnot do the job. Beyond will have moreresidual control than Express, the KSUweed scientist adds — something toconsider, given Palmer amaranth’s longgermination window.

As for the available preplant or pre-emerge herbicides, Spartan® is mostconsistent in performance and providesthe best degree of control of Palmeramaranth, Stahlman observes. Dual®and Prowl® will provide partial controlunder the right conditions, but don’thave the residual effect that Spartandoes, he remarks. “Spartan is probablyour preferred broadleaf weed controlherbicide,” Stahlman says. “But somegrowers are still using quite a bit ofProwl, and some are using Dual. Itdepends on the weed spectrum they’reanticipating.

“We do need to stay on top ofPalmer amaranth in sunflower, becauseit is such a highly competitive weed,”emphasizes the Kansas weed scientist.— Don Lilleboe �

Left: “Palmer amaranth will get just astall or taller than the crop, no matterhow tall the sunflower is. It just reachesfor the sun,” notes KSU weed scientistPhil Stahlman, shown here in a researchplot on the Hays station.

Palmer Amaranth Flexing Its MuscleAggressive Pigweed Species with Long Germination WindowRequires Close Attention in High Plains Sunflower Fields


Pho

to: D

on L

illeb

oe

The advent of no-till and conservation tillagegreatly changed herbicide use in sunflower.

Prior to the first Spartan (Sulfentrazone) labelin 1999, farmers were voicing the need for her-bicides that did not require mechanical incor-poration for activiation. Prowl (Pendimethalin)was the only choice at that time. However, ithad limitations as a ‘stand alone’ herbicide,unable to control all of the broadleaf andgrassy weeds that growers encountered. Theneed for mechanical soil incorporation reducedsoil moisture in the critical top two inches.

Treflan (Trifluralin) and Sonalan(Ethalfuralin) were two common soil-appliedherbicides prior to Spartan. Both need shallowincorporation. Eptam (EPTC) is another simi-lar product requiring incorporation that controlsmost grasses and some broadleaf weeds.

As sunflower moved further west along theU.S. Highway 83 corridor from Canada toTexas, these herbicides no longer fit the needto conserve moisture via reduced or zerotillage. Producers in this low rainfall areacould not tolerate drying out the top soil layer.

Dual Magnum® (S-metolachlor) waslabeled on sunflower in 2004. It provides moreflexibility since it does not need to be mechani-cally incorporated to be activated. However,the product does need rainfall or irrigation forincorporation — and tillage incorporationimproves consistency of control. Dual’s limita-tion in the northern states is the lack of controlof wild mustard and wild oat.

Rates for these soil-applied products relateto soil texture. For Dual Magnum, rates aregenerally higher on fine-textured soils with ahigh organic matter, while some other herbi-cides require a lower rate on light soils.

These products continue to serve importantmarkets in areas where conventional tillage

predominates. They also have value as tankmixes. Richard Zollinger, NDSU extensionweed specialist, likes Prowl in a Spartan tankmix. He finds that Prowl gives better season-long weed control compared to the other soil-incorporated products. He also finds that Dualdoes not perform as well in some of the north-ern areas due to high organic matter and fine-textured soils.

However, Dual tends to fit better in theHigh Plains. Phil Stahlman, Kansas StateUniversity weed scientist at Hays, recom-mends Dual as a tank mix with Spartan in hisarea. He finds better residual with Dual, andsays a second benefit may be enhanced con-trol of some of the difficult broadleaf weeds likePalmer amaranth. That, however, depends ona good rain event for incorporation.

Stahlman says the soil-incorporated herbi-cides other than Spartan have limitations for

broadleaves. “These products are for grassyweed control. Using one of these products incombination with Spartan becomes an eco-nomic issue for the grower.” Stahlman likesthe added grass control that either Dual orProwl provide in no-till or reduced tillage incombination with Spartan. He does not seemuch use of postemerge grass products incentral Kansas sunflower since growers tendto expect the sunflower plant’s aggressivegrowth to compete well with grassy weeds.

That may not be the case in the northernstates where cool soil and air temperaturescan delay early sunflower growth. CentralNorth Dakota producer Tim DeKrey does not

use either Dual or Prowl with his Spartan. Heuses Spartan Advance right after he plants(handling grasses at that time), then follows upwith a postemerge grass herbicide.

So what’s the future of these soil incorporat-ed herbicides? The simple answer is that

they are important weed control tools for sun-flower in a toolbox that is pretty thin to beginwith. There are very few new developments inherbicides these days, with glyphosate domi-nating the weed control market. Sunflowergrowers want to hang on to every herbicidethey have — and that includes the older soil-incorporated ones. — Larry Kleingartner �


Other Soil-IncorporatedHerbicides Still Needed

PowerBehindTheFlower.comPowerBehindTheFlower.com

PEOPLE RESEARCH KNOWLEDGE PERFORMANCE

Research powers the Pannar sunflower program. Now we want to empower you with online access to information for achieving premium potential on your sunflower acres. Discover research,

global and local breeding development, and hybrid management for powering your productivity.

We’re the Power Behind the Flower™ and we want to connect with you.

PowerBehindTheFlower.com

INTRODUCING

What’s Available for ’10Listing of Herbicides Currently Labeled for Use in Sunflower

Controls many grasses and certain broadleaf weeds. Apply just before plant-ing and incorporate immediately. Use the low rate on light-textured soils.

Controls grasses more effectively than broadleaf weeds. Apply before plant-ing and incorporate within 48 hours. Can control shattercane. Follow labeldirections.

Apply to control emerged weeds before or after sunflower planting but beforecrop emergence. Glyphosate products differ in concentration and adjuvantrequirements. Refer to specific product labels for rate and adjuvant recom-mendations. Condition spray solution with 1 to 2% spray-grade ammoniumsulfate by weight (8.5 to 17 lb/100 gal water) before adding glyphosate to thetank. Follow label directions.

Controls grasses and some small-seeded broadleaf weeds pre-emergence.Can be applied from 30 days before planting to crop emergence. Can beincorporated shallowly, but deep incorporation or excessive soil disturbanceat planting may result in poor weed control. Use lower rates on coarse soilswith low organic matter and the higher rates on fine-textured soils with high-er organic matter. Do not allow livestock to graze or feed in treated area.

A restricted-use pesticide. Apply before crop emergence for control ofemerged weeds. Paraquat is a contact herbicide and does not have soilactivity. Always apply with a nonionic surfactant to 0.5% v/v.

Controls grass weeds more effectively than broadleaves. Pendimethalin canbe applied from 60 days before planting until crop emergence. Incorporationgenerally improves weed control in conventional tillage systems. Extremelycool, wet weather following application and sunflower planting can result inproblems with sunflower emergence and injury. Do not feed forage or allowlivestock to graze in treated fields. Follow label directions. (Con’t)

Herbicide & Lbs/Ac Active

Ingredient Needed

Formulated Product/Ac*

Comments / Limitations

EPTC2 to 3

Ethalfluralin0.56 to 1.125

Glyphosate0.38 to 0.75 lb/ac

S-metolachlor0.95 to 1.91

Paraquat0.63 to 1.0

Pendimethalin0.5 to 1.5

The following listing of herbicides and use recommenda-tions comes from the 2010 Chemical Weed Control Guidepublished by the Kansas State University AgriculturalExperiment Station and Cooperative Extension Service.

Similar guides are published by universities in othermajor sunflower-producing states. While most of the infor-mation provided here would be applicable to other states aswell as Kansas, growers in those states are encouraged toconsult their own university’s 2010 sunflower weed controlinformation. Relevant websites for North Dakota, SouthDakota, Nebraska — and Kansas — include:

• North Dakota: www.ndsu.edu/weeds/• South Dakota: http://agbiopubs.sdstate.edu/

pub_description.cfm?Item=FS525OS• Nebraska: http://cropwatch.unl.edu/web/weed/home• Kansas: www.agronomy.ksu.edu/extension/The website of the National Sunflower Association also

contains significant information on weed issues and controlin sunflower. Go to www.sunflowernsa.com. Click on“Growers,” then “Weeds.”

As always, “the label is the law.” Read and follow labeldirections when using any of these products.

— Burndown, Preplant and/or Preemergence —

2.5 to 3.5 pt Eptam 7E or10 to15 lbs Eptam 20G

1.5 to 3 pt Sonalan

1 to 2 pt of 3 lb ae/galGlyphosate

1 to 2 pt Dual Magnumor Charger Basic

2.5 to 4 ptGramoxone Inteon

1.2 to 3.6 ptPendimethalin 3.3* or1.5 to 3 pt Prowl H20

*Products often are available in several formulations or brand names, and label information may vary.


Apply in the fall, preplant or pre-emergence to sunflower for control of pig-weeds, kochia, Russian thistle and certain other broadleaf weeds. The lowerrates are for coarse-textured soils with low organic matter, and the higherrates are needed on fine-textured soils with higher organic matter content.Preplant treatments 14 days or more before planting have generally providedbetter weed control and crop tolerance than pre-emergence applications atplanting time. Follow label directions.

Apply in the fall, preplant or pre-emergence to sunflower for burndown andresidual control of pigweeds, kochia and other broadleaf weeds. The lowerrates are for coarse-textured soils with low organic matter, and the higherrates are needed on fine-textured soils with higher organic matter content.May be tank mixed with glyphosate for improved grass burndown activity.

Apply in the fall, preplant or pre-emergence to sunflower for burndown andresidual control of pigweeds, kochia and other weeds. The lower rates are forcoarse-textured soils with low organic matter, and the higher rates are need-ed on fine-textured soils with higher organic matter content. Supplementalglyphosate is recommended for adequate weed control with the lowerSpartan Advance application rates.

Controls grasses more effectively than broadleaf weeds. Apply before plant-ing and incorporate within 24 hours. Can control shattercane. Follow label.

Controls annual and perennial grasses. Apply when grasses are activelygrowing but before they exceed size limits listed on the label. Apply Selectand comparable products with crop oil concentrate at 1% v/v. Apply SelectMax with nonionic surfactant at 0.25% v/v or crop oil concentrate at 1% v/vplus ammonium sulfate at 2.5 to 4 lbs/ac. Weed control is reduced if appliedwhen grasses are under drought stress. Do not apply within 70 days of har-vest. Do not allow grazing or use treated plants for feed or forage.

Apply to Clearfield sunflower only. Beyond will severely injure or kill non-Clearfield sunflower. Can be applied from the V2 through the V8 stage ofsunflower for control of susceptible broadleaf weeds before they exceed 3inches, and susceptible grasses before they exceed the 4- to 5-leaf stage.Apply with nonionic surfactant and nitrogen fertilizer additives. May notcontrol ALS-resistant kochia, pigweed or shattercane biotypes. Temporaryyellowing of sunflower plants may occur shortly after application of Beyond,especially when applied to crops growing under environmental stress. Donot plant corn, sorghum, cotton or non-Clearfield sunflower within 9 monthsof Beyond application.

Controls many annual and perennial grasses, including shattercane, volunteercorn and volunteer wheat. Apply with 1% v/v crop oil concentrate or 0.25%v/v nonionic surfactant. Weed control is reduced if applied when weeds areunder drought stress. Do not graze or feed forage, hay or straw from treatedareas to livestock. Do not apply within 60 days of sunflower harvest.

Controls annual and perennial grasses. Apply when grasses are growingactively but before they reach size limits listed on the label. Apply to annualgrasses up to 8 inches, volunteer corn up to 20 inches, shattercane from 6 to18 inches, volunteer wheat before tillering, and rhizome johnsongrass from15 to 25 inches tall. Higher rates are recommended in the western third ofKansas than in the eastern part of the state. Always apply with crop oil con-centrate or Dash. Weed control is reduced if applied when grasses are underdrought stress. Do not apply within 70 days of harvest. Do not use treatedplants for feed or forage. Follow label directions and precautions.

Apply to ExpressSun sunflower only. Express will severely injure or kill non-ExpressSun sunflower. Can be applied between the 1-leaf and the beginningof bud stage of sunflower growth for control of small, actively growingbroadleaf weeds. Apply with methylated seed oil at 1% v/v. May not con-trol ALS-resistant biotypes of kochia or pigweed. Temporary yellowing of

— Postemergence —

3 to 8 oz Spartan 4F

3 to 8.5 ozSpartan Charge

21 to 36 ozSpartan Advance

1 to 2 ptTrifluralin 4E*

6 to 16 oz Select,Arrow or Volunteer, or 9 to 16 oz Select Max

4 oz Beyond

5 to 12 ozAssure II or Targa

1 to 2 pt Poast

0.25 to 0.5 ozExpress TS


Sulfentrazone0.094 to 0.25

Sulfentrazone + Carfentrazone0.07 to 0.21 +0.008 to 0.023

Sulfentrazone +Glyphosate

0.09 to 0.16 +0.49 to 0.84

Trifluralin0.5 to 1

Clethodim0.07 to 0.25

Imazamox0.031

Quizalofop0.03 to 0.075

Sethoxydim0.1 to 0.28

Tribenuron0.0078 to 0.0156

sunflower plants may occur shortly after application of Express — especiallywhen applied to crops growing under environmental stress. Do not applywithin 70 days of sunflower harvest. Do not feed forage from treated areasor allow livestock grazing within 7 days of application. Allow 30 daysbetween application and feeding hay from treated areas to livestock.

Apply by ground or aerial equipment to control annual and perennial weedsand help facilitate harvest. Apply when sunflower seeds reach physiologicalmaturity (when seed moisture is 35% or less). For many sunflower varieties,this stage is when the backs of heads are yellow and bracts are turningbrown. Allow a minimum of 7 days between treatment and harvest for live-stock feeding.

A restricted-use pesticide. Always apply with nonionic surfactant. Applywith ground or aerial equipment 7 to 21 days before harvest to desiccatesunflower plants, broadleaf weeds and grasses. Apply when sunflower seedsreach physiological maturity (when seed moisture is 35% or less). For manyvarieties, this stage is when backs of heads are yellow and bracts are turningbrown. Do not allow grazing of treated areas or feed treated forage.

Apply by ground or aerial equipment to desiccate sunflower in order to facil-itate earlier harvest. Apply when sunflower reaches physiological maturity(when seed moisture is less than 35%). For many sunflower varieties, thisstage is when the backs of heads are yellow and bracts are turning brown.Apply with 1% v/v methylated seed oil plus 1.25 to 2.5% v/v liquid ureaammonium nitrate fertilizer or ammonium sulfate at 8.5 to 17 lbs/100 gal ofspray solution. Allow a minimum of 7 days between treatment and sun-flower harvest. Do not apply on sunflower grown for seed production.

Apply by ground or aerial equipment to facilitate harvest and reduce mois-ture in mature seed heads. Apply 7 or more days before harvest when seedheads are fully mature. Do not allow grazing of treated fields or feed treatedforage. �

— Harvest Aids —

Glyphosate0.75 lb ae

Paraquat0.3 to 0.5

Saflufenacil0.022 to 0.044

Sodium chlorate6

22 oz RoundupWeatherMax, Roundup

Original Max orRoundup PowerMax

1.2 to 2 ptGramoxone Inteon

1 to 2 oz Sharpen

1 gal Defol 6


Below: Symptoms of Assert injury to a young sunflower plant.

flower growth and under the right environmental conditions.For growers using a Clearfield or ExpressSun variety,

Beyond and Express will do a good job of controlling wildmustard. With non-herbicide-tolerant varieties, however, theonly option other than Assert is Spartan — and Spartan onlysuppresses mustard (40-50% control, according to NDSU).

While Assert is an important component of the sunflowerherbicide arsenal, use of this product also carries risk of seri-ous crop injury — particularly if applied under high tempera-ture and high humidity. Variety, growth stage, weather con-ditions, humidity, spray volume and additives all can influ-ence the herbicide’s safety for sunflower. Damage can rangefrom plant stunting to head deformation.

North Dakota State University advises applying Assertonly when air temperature (Fahrenheit) plus relative humiditytotals less than 150. NDSU also cautions against usingAssert on sunflower that is under drought or heat stress.

Recent years’ research by Brian Jenks, weed scientist withthe NDSU North Central Research Extension Center atMinot, has investigated several facets of sunflower cropinjury and yield after treatment with this herbicide. In 2009specifically, Jenks looked at Assert when applied with NIS,compared to a tank mix with a grass herbicide (Select®) andoil adjuvant (MSO); at the influence of an early application(four- to six-leaf stage) versus a late one (10-leaf stage); andat the effect of spray boom height above the sunflowercanopy. Study results can be viewed at www.ag.ndsu.edu/NorthCentralREC/weed-science-research. �

Avoiding Crop Injury WhenUsing ‘Assert’ for Mustard

Pho

to: R

ich

Zol

linge

r /

ND

SU

Numerous producers have applied the postemergent her-bicide Assert® to control infestations of wild mustard in theirsunflower. And it works. Grower experience and universitystudies through the years have confirmed the effectiveness ofAssert on mustard when applied at the proper stage of sun-

Weed Control In Sunflower - National Sunflower … across the country are accus-tomed to the...

Documents

Transcript of Weed Control In Sunflower - National Sunflower … across the country are accus-tomed to the...