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Corn Herbicides '99 Weigh your risks

How adverse to risk are you? Would you alternate Roundup Ready corn and soybeans annually in the same field? Would you go total post in both corn and soybeans?Whatever the case, challenge yourself to do what the most innovative, profit-driven farmers do: Experiment and don't sit still. Explore new and different mechanical and herbicide weed control practices to seek a more effective program that registers higher numbers on the yield monitor.

What's hot for 1999. Some university researchers and marketing executives don't see Roundup Ready (RR) capturing a large number of corn acres like it did in soybeans, primarily because of application timing. "Our research shows corn growers like a soil-applied approach for weeds and so do custom applicators because they don't want their rigs sitting idle until post corn application season," says Rob Schrick, Rhone-Poulenc's product lead for Balance herbicide. "Applicators have soybean acres ready at the same time corn needs spraying, and they just can't get all the acres in."

Monsanto estimates 3 to 4 million acres of RR corn in 1999. Aside from promoting two Roundup applications on RR corn, Monsanto also promoting cut rates of its preemergent herbicides for growers looking to reduce potential risk.New Chemistry. Balance herbicide from Rhone-Poulenc is a soil-applied tool for control of waterhemp, woolly cupgrass, velvetleaf and wild proso millet. For 1999, it is labeled for use in 16 states, but not in Minnesota, Wisconsin and Michigan because of an EPA request for more off-site movement studies in surface water and from physical drift. Schrick believes that these states will be added to the label, but probably not until 2001.

Best fit for this low-dose (2 oz./acre) product is as a foundation herbicide to control 40 broadleaf weeds and grasses (including ALS and triazine-resistant weeds). "Rarely used as a standalone, it'll be tank mixed with atrazine (up to 11/2 lbs./acre) or with a reduced rate (up to 50% less) of almost any preemergent herbicide, such as Harness, Surpass, Dual, Frontier, Axiom (which also is sold as a premix called Epic) and others," Schrick says. "It also has a good fit in any tillage system because of its strong burn-down capabilities (when mixed with crop oil or MSO) and 8 to 10 weeks residual.

"Of the farmers who have tried Balance, the number one attribute they like is its recharge ability, followed by its weed control spectrum, resistant weed control and low dose chemistry," Schrick says. "We have seen a lot of recharge over the last couple years. A farmer will get a half-inch rain or more that recharges the herbicide activity, and the weeds (2 in. tall or smaller) that did happen to emerge turn white and die."

Application timing is from 14 days prior to planting up to crop emergence. "And we're hoping to add an addendum to the label that will allow application up to 30 days before planting if using RR or Liberty Link corn," Schrick adds.Balance will be offered, as part of a joint marketing agreement, in Bayer's new Epic herbicide, a premix of the active ingredients in Balance and in Bayer's new Axiom. Epic is a soil-applied product for grass and broadleaf weed control, applied up to 14 days before planting at rates from 8 to 15 oz./acre, depending on soil texture (12 oz. average rate).

"We see strengths with Epic especially in the northern Corn Belt to control velvetleaf, woolly cupgrass, fall panicum, small seeded broadleaf weeds and all key grasses," says Inci Dannenberg, Bayer's product marketing manager. When asked of its challenges, she recommended a tankmix with a low rate of atrazine to get morningglories, cocklebur, sunflower, smartweed and giant ragweed.Rhone-Poulenc's Schrick likens an 11-oz. rate of Epic as a replacementfor Bicep, and the 15-oz. rate as a replacement for Bicep followed by Marksman.Axiom, new from Bayer last April, offers good residual (spray up to 45 days before planting), good control of key grasses and some small seeded broadleaf weeds, but will need a tankmix partner for difficult weeds (see chart).In the new-chemistry, postemergent category, two herbicides are ready: Distinct from BASF and Aim from FMC.

Distinct is a premix of a low rate of dicamba (Banvel) plus a new mode-of-action ingredient called diflufenzopry. "It is self-sufficient on broadleaf weeds, but we anticipate an Accent tankmix label to control grasses, although it has some activity on grass to help these herbicides work better," says Robert Simpson, corn marketing manager for BASF. "When applied on 4- to 24-in. corn, with less than 10 in. being the target, this post product provides enough residual control to last through canopy, without the application timing or carryover complications of many conventional products." The company anticipates receiving registration in late February.

Aim herbicide from FMC also offers new chemistry for fast-acting post broadleaf weed control. Approved for use in September as one of the first reduced risk products, it is being marketed as a $4/acre tankmix additive to control six of the toughest broadleaf weeds that other products often miss: velvetleaf, redroot pigweed, black nightshade, common lambsquarter, and ivyleaf and pitted morning glories.

"Many products have escapes on these five weeds. Aim is designed to make a lot of tankmix partners out there better," says Mike Snyder, FMC's product manager for Aim. Applied at only 1/3 oz./acre on 4-in. weeds, it is claimed to be "death on velvetleaf." One word of caution though: Aim regularly causes speckling of corn leaves, but the manufacturer claims that the speckling goes away in 7 to 14 days without harming yield. And the label says do not mix with crop oil or an EC (oil-based) formulation.

Herbicide resistance. Last year RR corn hybrids were only available from DeKalb. This year at least 80 of the 170 licensed companies will have at least one RR corn hybrid, except for Pioneer, Northrup King and Cargill which do not have agreements with Monsanto. Holden's will be supplying germ plasm to many smaller companies requesting it.

This year growers can use sequential in-crop applications of Roundup Ultra of 24 or 32 oz./acre, not to exceed 64 oz. total, which can now be applied on corn up to 30 in. tall (V-8 stage). But timing is critical. Or, you can apply a half-rate of a Monsanto preemergence corn herbicide followed by a Roundup application as needed.

"With the timing you need, to avoid early weed competition, the initial Roundup application must be made before weeds are 4 in., says Norm Probst, corn technical manager for Monsanto. "Then, due to this early application, you're going to need to make a second application because you'll usually have a second flush of weeds. That second application would come about the time you'd be putting on soybean products. So you may want to consider the flexibility of using residual herbicides if they fit your operation better."

AgrEvo, which claimed to capture 2 million acres worth of Liberty Link in 1998, has added a new premix of Liberty and atrazine for 1999 called Liberty ATZ. "We added this premix because the combination adds more than either one alone," says Bill Bertges, AgrEvo's Midwest field development manager. "Our 32 oz./acre rate contains 8/10 lb. of atrazine and the 40-oz. rate uses 11/4 lbs. atrazine. And by adding AMS you improve absorption.

"Our fit with Liberty has been in waterhemp and woolly cupgrass country, and we work well on other tough weeds such as wirestem muhly, quackgrass and nutsedge (with Dual or atrazine down)," he says.

Cyanamid's Lightning herbicide, for use on IMI corn, is claimed to have covered 11/2 million acres in 1998. "We have no major label changes, other than adding drop nozzles when spraying 20+ in. of corn in the southern Corn Belt to get Johnsongrass," says Barney Bernstein, Lightning product manager. "The best change is on the seed side, where we'll have more Bt/IMI stacked hybrids available."

The latest premixes. Celebrity from BASF is a co-pak bag that combines leading grass and broadleaf post products - 2/3 oz./acre of nicosulfuron (Accent) and 6 oz./acre of dicambate (Banvel) - and covers 8 acres without measuring. It works best applied early post, when broadleaves and grasses are less than 3 and 4 in. tall, respectively.

Leadoff from DuPont contains the same active ingredients found in Frontier and atrazine, and is the same as Guardsman herbicide from BASF. It is designed for use as a preplant, from several weeks before planting up to corn emergence - either in a one-pass program or two-pass where Leadoff is followed by Basis Gold.

NorthStar from Novartis is a premix of the active ingredients in Beacon and Banvel, targeted to control 31 broadleaves and five grasses in the Corn Belt north of I-80. The company recommends using a soil-applied grass herbicide such as Dual II Magnum or Bicep II Magnum followed by NorthStar at 5 oz./acre on 4 to 12 in. tall corn.

Spirit, also from Novartis, contains the same active ingredients as Exceed (Beacon and Peak), but with 50% less Peak to reduce carryover concerns. It is targeted for use south of I-80 and north of I-70 where you can rotate to soybeans 10 months after application. The company recommends applying 1 oz./acre post (prior to June 30) following a soil-applied grass herbicide such as Dual II Magnum or Bicep II Magnum.

1999 corn herbicide update - Post applied

Aim Site of action: 14 FMC$4/acre

Label rate is 1/3 oz./acre on 1- to 4-in. broadleaf weeds. Application windowextends up to the eight-leaf collar stage or 24- in. tall corn.

NEW PRODUCTRegistered for use last September, this post broadleaf herbicide offers a newmode of action due to a unique active ingredient, carfentrazone-ethyl. And it is one of the first products classified as reduced risk by the EPA.


Used alone it controls velvetleaf, redroot pigweed, black nightshade, commonlambsquarter and ivyleaf and pitted morningglories. Biggest strength comes whenused as an economical tankmix partner for improved control of weeds such asALS- and triazine-resistant weeds, waterhemp, pigweeds, common cocklebur andmore. Check the label for tankmix partners, because it is not compatible with ECformulations and crop oil concentrate. Some corn leaf burn or speckling mayoccur, but the company says there is no impact on yield.

Celebrity Site of action: 2+4 BASF $23/acre

It is most effective when applied early post (less than 3-in. tall broadleaves and 4-in. grasses), and used with a non-ionic surfactant, UAN, or ammonium sulfate.


Registered for use last March, this is a bagged, co-pak premix of sodium salt ofdicamba (Clarity/Marksman) and nicosulfuron (Accent). There is no need to figurerates; each bag covers eight acres.


It offers grass and broadleaf weed control in one post product, without need fortankmixing. It offers control of tough weeds such as foxtail, woolly cupgrass,cocklebur, lambsquarters, waterhemp and Canada thistle. And since it offers anon-ALS mode of action on broadleaves, it gives growers another weedresistance management tool.

Distinct Site of action: 4 BASF Not available until product registration

Recommended rate is 6 oz./acre when corn is 4 to 10 in. tall. The knockdownrate is 4 oz./acre on 10- to 24-in. corn.


Distinct is a premix of the active ingredients sodium salt of dicamba (Banvel) and a new mode-of-action ingredient called diflufenzopyr. Registration is pending for the 1999 season.


It provides good control of most significant broadleaf weeds like waterhemp,ALS- and triazine-resistant weeds, Canada thistle, pigweed, lambsquarter,morningglory, velvetleaf and cocklebur, along with some suppression of grasses.Distinct can be used in a program with a pre or post grass herbicide for total grass and broadleaf control. The manufacturer claims that it offers residual control up through crop canopy, a wide application window, and fast action on weeds (as little as 4 hrs.). The lower rates of dicamba should reduce crop injury potential compared to competing products.

NorthStar Site of action: 2+4 Novartis$10/acre

The company recommends using a soil-applied grass herbicide such as Dual IIMagnum or Bicep II Magnum followed by a post application of NorthStar at 5oz./acre on corn between 4 and 12 in. tall.


Approved by EPA last fall, this premix of primisulfuron (Beacon) and dicamba(Banvel) is primarily targeted for use in the Corn Belt north of I-80.


It controls 31 broadleaf weeds, including waterhemp and Canada thistle, and fivegrasses, including shattercane and quackgrass. With two different chemistries and two modes of action, it is a good tool to manage/prevent ALS andtriazine-resistant weeds. There are no pH or organic matter restrictions, andsoybeans can follow within 8 months after an application.

Spirit Site of action: 2 Novartis $11/acre

The company boasts that only 1 oz./acre of Spirit is needed following asoil-applied program of Dual II Magnum or Bicep II Magnum. Postemergentapplications must be made prior to June 30. When Spirit is applied after that date, you must rotate to corn, sorghum, or small grains. Read the label for specifics.


Approved for use last year, this premix contains the same active ingredients asExceed (Beacon + Peak), but it has a 50% lower rate of prosulfuron (Peak) toreduce carryover concerns and a higher rate of Beacon for improved grasscontrol. Use is targeted on corn grown south of I-80 and north of I-70, where you can rotate to soybeans 10 months after application.


It controls 34 broadleaf weeds and shattercane, while suppressing 15 otherbroadleaf weeds and grasses. It features up to three weeks residual control and is safe to use on corn from 4 to 24 in. tall.

SITES OF ACTION: 2. ALS/AHAS; 4. Synthetic auxins; 14. Protoporphyrinogen oxidase.

1999 corn herbicide update - Soil Applied

Axiom DFSite of action: 5+15Bayer$17.50 to $18.50/acre (17-oz. rate)

Rate ranges from 13 to 23 oz./acre depending on soil texture, organic matter,

tillage practice and application timing. A 17-oz. rate is claimed to provideconsistent control on most medium Midwest soils. It can be applied under anytillage system up to 45 days before planting and is compatible with liquid fertilizer.

The dry flowable formulation is available in 25-lb. containers or in its new patented Accu-Bin pneumatic delivery system that holds 1,000 lbs. of product to treat 800 to 1,000 acres.


This soil-applied grass (and selected broadleaf) herbicide for both corn andsoybeans received federal approval last April. It is a combination of new chemistry (an oxyacetamide herbicide) that interferes with seed germination and seedling development, and a low rate of metribuzin (active ingredient in Sencor).


Claimed to be a good grass-control foundation product, it also adds control ofsome small seeded broadleaves like lambsquarter, pigweed, and tall and commonwaterhemp. For challenging grasses such as shattercane, sandbur, woollycupgrass, yellow nutsedge and wild proso millet, or tough broadleaf weeds suchas velvetleaf, nightshade, common ragweed, sunflower, jimsonweed, mustard orsmartweed, a tankmix is needed.

BalanceSite of action: 28Rhone-Poulenc$16/acre for 2 oz./acre rate

Apply it preplant surface or incorporated up to 14 days prior to planting until crop emergence. Standard rate is 2 oz./acre. It provides residual control for 8 to 10 weeks, and control can be "recharged" with a 1/2-in. rain, allowing it to control existing weeds up to 2 in. tall. Depending on weed spectrum, it can be tank mixed with all popular soil-applied herbicides at reduced rates (up to 50%).


This new preemergent herbicide contains new chemistry and a new mode ofaction. It received EPA approval last September for use in 16 states initially(Wisconsin, Minnesota and Michigan are excluded in the Midwest).


Balance is claimed to control more than 40 broadleaf weeds and grasses, with itsbest fit on velvetleaf, tall waterhemp, woolly cupgrass and wild proso millet. For fields with a history of yellow foxtail, cocklebur, sunflowers, wild buckwheat, giant ragweed or morning glories, a tank-mix partner or subsequent use of a post product and/or cultivation may be needed, especially on late-emerging weeds (like cupgrass and waterhemp).

EpicSite of action: 15+28Bayer and Rhone-Poulenc$23 to $25/acre

Apply 8 to 14 oz./acre (12 is average) depending on soil texture. Apply 14 daysprior to planting.


Epic is a new premix containing one of the active ingredients in Axiom (flufenacet)and the active ingredient in Balance (isoxaflutole). This soil-applied product controls grasses and broadleaves in field and silage corn; it was approved for use last November.


Epic fits well in the Corn Belt due to strengths on velvetleaf, woolly cupgrass, fall panicum, small seeded broadleaves, and all key grasses. Challenges includemorningglories, cocklebur, sunflower, smartweed, shattercane and nut sedges.

LeadoffSite of action: 5+15DuPontOne pass = $18 to $20/acreTwo pass = $21 to $22/acre

For one pass, apply 41/2 to 5 pints/acre 45 days before planting up to 8-in. tall corn. For two pass, use 11/2 pints/acre, followed by 14 oz./acre of Basis Gold, approximately 3 to 5 weeks after corn emergence.


Approved for use last October, Leadoff is a premix of Frontier and atrazine,which can be applied preplant, PPI, preemergence or early postemergence.BASF markets the same product, called Guardsman.


The manufacturer claims that it offers residual control of a broad spectrum of grass and broadleaf weeds when used in a two-pass program with Basis Gold. It can also be used alone as a replacement for Extrazine II.

SITES OF ACTION: 2. ALS/AHAS; 5. Photosystem II (PS); 15. Unknown; 28.4-hydroxy-phenyl-pyrurate-dioxygenase.

1999 corn herbicide update - Herbicide/Seed Combo

Liberty ATZSite of action: 5+10AgrEvo $16 to $20/acre

The best soil/post program is a reduced rate of a preemerge herbicide (or 1 to11/2 lbs. atrazine/acre) followed by a post application of Liberty ATZ (32 to 40oz./acre) plus AMS (3 lbs./acre). For total post application, apply Liberty ATZ(32 to 40 oz./acre) plus AMS (3 lbs./acre). Apply before corn is 12 in. tall andweeds are 4 in., in general.


Approved for use in September by the EPA, this new premix of Liberty plusatrazine controls more than 100 grass and broadleaf weeds when used withLiberty Link or other warranted glufosinate-resistant corn.


This nonselective herbicide controls a broad spectrum of small grasses andbroadleaves in 2 to 4 days, including foxtails, cocklebur, velvetleaf, tallwaterhemp, pigweeds and especially ALS-resistant weeds. Atrazine will supplysome residual control depending on soil texture, organic matter and use rate.

Roundup Ultra (for Roundup Ready corn)Site of action: 9Monsanto$15 to $20/acre plus $6/acre technology fee, depending on soil-applied productsor sequential Roundup Ultra treatments.

New sequential applications have been added for 1999. Apply a reduced rate (50to 75%) of any Monsanto residual herbicide preemergence followed by RoundupUltra in-crop. Or tank mix a reduced rate (50 to 75%) of Harness, Harness Xtra,or Xtra 5.6L before corn exceeds 11 in. tall; or with Micro-Tech, Partner orBullet postemergence (before corn exceeds 5 in. tall) with Roundup Ultra.Atrazine has been added to the approved list of tankmixes with Roundup Ultra.


For 1999 use on Roundup Ready (RR) corn, up to two in-crop applications cannow be made until the V8 stage of corn (8 leaves with collars) or until the cropreaches 30 in. tall. The maximum rate also has been increased to 64 oz./acre, with a maximum of 32 oz./application.


It offers effective control of more than 100 grasses and broadleaf weeds and vines. There are three aspects to consider with this program: Volunteer RR corn in RR soybeans the following year will need added chemistry with Roundup for control; do not graze livestock or feed any RR corn grain/silage following sequential Roundup Ultra applications; regulatory export approval of RR corn grain to certain countries may not be fully achieved by harvest, so grain must be used for on-farm livestock feed or sold to domestic-use markets only.

SITES OF ACTION: 5. Photosystem II (PS); 9. EPSP synthase; 10. Glutamine synthetase;15. Unknown.

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