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Managing Weeds 

Weed identification is the key to an effective corn weed management program. Incorrect identification of problem weeds can mean the difference between profit and loss. Although a weed’s life cycle, including its method(s) of reproduction, is the most important identifying characteristic, it is sometimes necessary to know the exact species before selecting weed management measures.

Corn growers should make a weed inventory to aid in the selection of weed control programs. By tailoring control programs to fit the problems in each field, growers can minimize weed control costs while maximizing yields and profits. An inventory can be made by scouting fields two or three times during the year and recording the types (such as broadleaf annuals or annual grasses) of weeds present in each field.

The first observation should be made by the time corn is 3 or 4 inches tall. These early-season observations reveal how effective preplant or preemergence herbicides, if used, have been and suggest the possible need for cultivation or for postemergence herbicide applications. A second look at the fields in midsummer (before the corn is waist high) can provide information on the overall effectiveness of weed control practices and provide clues on how the program might be adjusted in future years. This also is a good time to record the types and numbers of weeds present and to map the location of special problem areas in the field. Additional notes on weed types and numbers can be taken at harvest to complete the weed inventory.

Weed Management Methods
Although herbicides can provide effective weed management, corn growers should not depend on herbicides alone. Growers should use good cultural practices so the corn is competitive with any weeds and should integrate chemical control programs with cultivation, especially with difficult-to-control weeds or when weather conditions reduce herbicide effectiveness.

The first step in cultural weed control is the selection of a corn hybrid that is adapted to local growing conditions. Timely planting along with proper fitting in tilled situations or proper adjustment of no-tillage planters ensures rapid germination and a competitive advantage for the corn. Another cultural practice that favors rapid establishment of corn is proper band application of fertilizer at planting.

All primary (plowing) and secondary (fitting) tillage operations help provide a weed-free seedbed. Cultivation of row crops is an effective way to control annual weeds between corn rows. Band application of herbicides over the row at planting, combined with one or two cultivations, provides good control of annual weeds such as common lambsquarters and foxtails. Although rotary hoes effectively destroy weed seedlings in small corn, a row cultivator adjusted to minimize pruning of corn roots should be used after corn is 5 or 6 inches tall. Creeping perennials such as common milkweed and quackgrass are not adequately controlled by one or two cultivations. These weeds regrow from rhizomes (underground stems) following cultivation and are controlled with tillage only if the operations are repeated over long periods. Biennial (wild carrot, etc.) and simple perennial (dandelion, etc.) weeds do not persist in fields that are plowed but can be a problem in reduced and zone/no-tillage fields.

A variety of herbicides are available for preplant, preemergence, and/or postemergence weed control in corn. These herbicides vary in their effectiveness in controlling different weeds (Table 3.7.1) and in the length of time they remain active in the soil. Some corn herbicides, such as *atrazine and Princep, can carry over to affect triazine-sensitive rotational crops such as small-seeded forage legumes, small grains, and soybeans. Knowledge of the weeds present, herbicide effectiveness, and rotational plans should be considered when selecting herbicides.

Cost of chemical weed control dictates that herbicides be applied when they will provide maximum return. Label guidelines for the timing of herbicide applications are based on research and are geared for maximum weed control and minimum crop injury. The labeled application timings for corn herbicides are shown as shaded cells in Table 3.7.2.

Factors Affecting Soil-Applied Herbicides
To be effective, soil-applied herbicides must be available for uptake by the roots and/or shoots of germinating weed seedlings. This means that they must be dissolved or suspended in the soil solution. Soil properties that affect the availability and activity of soil-applied herbicides include soil texture, organic matter level, and pH. All should be considered when determining herbicide rates.

Soil texture is determined by the relative percentages of sand, silt, and clay in a soil. Names describing texture such as loamy sand and clay loam are assigned to soils depending on these percentages. Clay particles are negatively charged and have a large surface area. As a result, soils high in clay content (heavy soils) have the capacity to adsorb or tie up herbicides and generally require higher herbicide rates than coarse-textured or light soils.

Organic matter content also affects adsorptive capacity of soils. Although un-decomposed plant and animal residues can influence herbicide performance, the well-decayed, fine organic matter particles known as humus are of greatest importance. Like clay particles, humus particles are negatively charged but exhibit an even greater capacity to adsorb or tie up herbicides than clay. Consequently, herbicide rates also have to be adjusted to the soil organic matter level.

Rates for soil-applied herbicides in the chemical weed control tables (Tables 3.7.3, 4.11.1 and 6.7.2) are for medium-textured (loam) soils with organic matter levels of 3 to 4 percent. Fine-tuning the rates for other soils can be done by consulting the herbicide label for different soil textures and for varying organic matter levels.

Soil pH can also affect the availability of some soil-applied herbicides. This is important for the triazine herbicides (*atrazine and Princep). These herbicides are most strongly adsorbed (tied up and unavailable for uptake by weeds) on clay and organic matter particles at low pH levels. Although the amount of triazine adsorption increases at all pH levels below 7.0, adsorption is most dramatic at pH levels of 6.0 and below. This is an important consideration for contin-uous zone/no-tillage fields where the surface inch of the soil profile may have a lower pH than is reflected in the results of a normal soil sample analysis. It may be helpful to check the pH in the top inch of the soil profile with a soil pH kit in fields that have been in zone/no-tillage for extended periods.

Soil pH also affects availability of †Python WDG (flumetsulam) and soil applications of *†Hornet WDG (clopyralid + flumetsulam). These herbicides should not be applied to areas where soil pH is greater than 7.8 as this may result in unacceptable crop injury. In addition, soil applications of †Python WDG or *†Hornet WDG should not be made to soils with more than 5% organic matter if soil pH is less than 5.9 as reduced weed control will result.

Herbicide Resistance Management
Triazine-resistant biotypes or strains of common lambsquarters, smooth pigweed, common ragweed, and common groundsel have been confirmed in New York State. Populations of these weeds were originally controlled with one or more of the triazine herbicides (*atrazine and Princep) at normal use rates; however, shifts to weed populations dominated by the triazine-resistant strains have occurred in many locales. These triazine-resistant strains are not controlled with extremely high triazine use rates. In addition, there is cross-resistance among the different triazine herbicides used in corn, soybeans (Sencor), and alfalfa (Sencor and Velpar).

This situation has prompted refinements in the control guidelines for annual broadleaf weeds in field corn. Triazine herbicides have played, and will continue to play, an important role in field corn weed control programs; however, effective control programs for these triazine-resistant strains will involve the use of crop rotation and cultivation along with herbicide rotation and/or use of herbicide combinations that include herbicides with different sites of action (how they affect weeds). These practices will also delay development of weed populations that are resistant to triazine and other herbicide groups.

Rotating herbicides with different sites of action and the use of tank mixes or sequential applications that involve herbicides with different sites of action are key elements in herbicide resistance management plans. To do this most effectively, everyone involved in decisions about weed management must have site of action classification for herbicides readily available. The Weed Science Society of America (WSSA) has approved a numbering system to classify herbicides by their site of action (Mallory-Smith, C.A. and Retzinger, E.J. 2003. Revised classification of herbicides by site of action for weed resistance management strategies. Weed Technol. 17:605-619). In this system, a group number is given to all herbicides with the same site of action. To further efforts in management of existing herbicide-resistant weed populations and to delay or avoid development of new herbicide-resistant weed populations, these “GROUP NUMBERS” are included in the “Chemical weed control tables in each crop section of this guide. Since herbicide resistance management is most effective when practiced across all crops in rotation, “GROUP NUMBERS” for all herbicides in the Cornell Guide For Integrated Field Crop Management can be found in Table 8.2.1. Mode of action/site of action and chemical families for site of action groups can be found in Table 8.2.2.

Weed Control in Zone/No-Tillage Corn
Weed control in zone/ no-tillage corn is more difficult than in reduced or conventionally tilled and planted fields for two reasons. First, some weed control options are eliminated in zone/ no-tillage cropping systems. Second, some weeds are more aggressive and/or more difficult to control in zone/ no-tillage situations. Effective control programs require proper identification of the existing and potential weed problems and knowledge of herbicides available. Chemical weed control in zone/ no-tillage corn may involve the following:

1.     Control of existing vegetation, before or at the time of planting, with a burndown herbicide. Herbicides used for this purpose include *Gramoxone Inteon or the various formulations of glyphosate including Roundup products, Durango DMA, Touchdown Total, etc. If burndown applications are made in combination with residual (preemergence) herbicides, they eliminate competition from existing vegetation long enough to get the corn established and to allow for rainfall activation of the residual herbicides. If residual herbicides are not used, burndown treatments provide a window for total postemergence weed control programs to be applied. With herbicide-resistant corn, like glyphosate-resistant (Roundup Ready) or Liberty Link hybrids, burndown and residual herbicides may be applied early postemergence in one-pass.

2.     If residual herbicides are not applied with the burndown application, weed control in zone/no- tillage corn may require preemergence or early postemergence herbicide applications to control weeds that emerge after planting. In addition, postemergence herbicides may be required to control escaped weeds such as dandelion.

Zone/no-tillage burndown guidelines are given in Table 3.7.4. Refer to Table 3.7.3 for preemergence or total postemergence weed management guidelines for field corn.

Prepackaged Herbicide Mixtures
There are many prepackaged herbicide mixtures for field corn. Although it is usually known which herbicides are included, questions do arise about the relative amounts of each herbicide in these mixtures. Information about the active ingredients in some of these products is summarized in Table 3.7.5.

Prepackaged herbicide mixtures eliminate the inconvenience of tank mixing herbicides to obtain broad spectrum (grass and broadleaf) weed control needed in most fields. Not only do they make spraying easier, but they can eliminate some of the problems associated with container disposal. Finally, these mixtures often can be purchased for less than the cost of equivalent amounts of the individual products. The disadvantage of these premixes is that the user sacrifices some flexibility in adjusting the rates of each herbicide to what is needed in a given situation.

 *Atrazine Application Rates

*Atrazine applications for corn are restricted to a maximum of 2.5 pounds active ingredient per acre (lb. ai/A) per calendar year. In addition, there is a per-application maximum of no more than 1.6 or 2 lb. ai/A depending on soil erodibility (as defined by NRCS) and the amount of crop residue cover.

For preplant and preemergence applications on highly erodible soils with more than 30 percent crop residue cover, use up to 2 lb. ai/A (4 pt./A) per application. For highly erodible soils with less than 30 percent crop residue cover, use 1.6 lb. ai/A (3.2 pt./A). On soils that are not highly erodible, use up to 2 lb. ai/A (4 pt./A). For postemergence applications, a maximum of 2 lb. ai/A (4 pt/A) may be applied if no *atrazine was applied before corn emergence. If a postemergence treatment is required following a preplant or preemergence application, the total *atrazine applied may not exceed 2.5 lb. ai/A (5 pt./A) per calendar year.

Calculating the lb. ai/A of *atrazine is relatively simple when using products that contain *atrazine only. It may be difficult to calculate the total amount of *atrazine being applied when using prepackaged herbicide mixtures. This is especially true if both preplant/preemergence and postemergence premix products are being used. Table 3.7.6 gives common labeled application rates of each premix product along with the lb. ai/A of *atrazine being applied.


 

Table 3.7.1. Effectiveness of selected corn herbicides on annual weeds.

Broadleaf Annual Weeds

Herbicides

Wild Buckwheat

Common Lambsquarters

Wild Mustard

Redroot Pigweed

Common Ragweed

Velvetleaf

Preplant-incorporated

 

 

 

 

 

 

 

*†Dual II Magnum/*†Cinch

Poor

Poor

Poor

Fair

Poor

None

Preemergence

 

 

 

 

 

 

 

*AAtrex/*Atrazine1

Excel

Excel1

Excel

Excel1

Excel1

Fair

 

Callisto

Poor

Excel

Good

Excel

Fair

Excel

 

*†Dual II Magnum/*†Cinch

Poor

Poor

Poor

Good

Poor

None

 

*†Micro-Tech

Poor

Fair

Poor

Good

Poor

None

 

*†Outlook

Poor

Poor

None

Good

Poor

None

 

Princep1

Good

Good1

Good

Good1

Good1

Fair

 

Prowl/Pendimax

Fair

Excel

Fair

Fair

Poor

Good

Postemergence

 

Accent Q

–––

Poor

Good

Good

Poor

Poor

 

Aim

–––

Good

Fair

Good

Poor

Excel

 

*Atrazine + oil1

Excel

Excel1

Excel

Excel1

Fair1

Good

 

Banvel/Clarity

Excel

Excel

Good

Good

Good

Good

 

*Beacon

–––

Fair

Good

Good

Excel

Good

 

Buctril

Good

Excel

Fair

Poor

Fair

Good

 

Callisto

Poor

Excel

Good

Excel

Fair

Excel

 

Impact

–––

Excel

Excel

Excel

Excel

Excel

 

Laudis

Fair

Excel

Excel

Excel

Excel

Excel

Table 3.7.1. Effectiveness of selected corn herbicides on annual weeds.

Herbicides

Wild Buckwheat

Common Lambsquarters

Wild Mustard

Redroot Pigweed

Common Ragweed

Velvetleaf

 

NorthStar

Good

Good

Good

Good

Excel

Good

 

Permit

–––

Poor

Fair

Good

Excel

Excel

 

Prowl/Pendimax

–––

Good

Poor

Good

None

Excel

 

Resolve Q

–––

Fair

Good

Good

Fair

Fair

 

Resource

–––

Poor

Fair

Poor

Fair

Excel

 

Spirit

–––

Good

Good

Good

Excel

Good

 

*Status

Excel

Excel

Good

Good

Good

Good

 

Steadfast Q

–––

Fair

Good

Good

Poor

Good

 

Yukon

–––

Excel

Excel

Excel

Excel

Excel

Annual Grass Weeds

Herbicides

Barnyardgrass

Large Crabgrass

Foxtails

Fall Panicum

Witchgrass

Corn Tolerance

Preplant-incorporated

 

 

 

 

 

 

 

*†Dual II Magnum/*†Cinch

Good

Good

Good

Good

Good

Good

Preemergence

 

 

 

 

 

 

 

*AAtrex/*Atrazine1

Good

Poor

Fair

Poor

Excel

Excel

 

Callisto

None

Fair

None

None

None

Excel

 

*†Dual II Magnum/*†Cinch

Excel

Excel

Excel

Excel

Excel

Good

 

*†Micro-Tech

Excel

Excel

Excel

Excel

Excel

Good

 

*†Outlook

Excel

Excel

Excel

Excel

Excel

Good

 

Princep1

Good

Good

Good

Good

Good

Excel

 

Prowl/Pendimax

Excel

Excel

Excel

Excel

Excel

Good

Postemergence

 

 

 

 

 

 

 

Accent Q

Good

Fair

Good

Fair

–––

Good

 

Aim

None

None

None

None

None

Good

 

*Atrazine + oil1

Poor

Fair

Poor

Fair

Good

Good

 

Banvel/Clarity

None

None

None

None

None

Fair

 

*Beacon

Poor

Poor

Fair

Fair

–––

Good

 

Buctril

None

None

None

None

None

Good

 

Callisto

None

Good

None

None

None

Excel

 

Impact

Good

Good

Fair

Fair

–––

Good

 

Laudis

Good

Good

Good

None

-----

Good

 

NorthStar

Poor

Poor

Fair

Fair

–––

Fair

 

Permit

None

None

None

None

None

Good

 

Resolve Q

Good

Fair

Good

Good

–––

Fair

 

Prowl/Pendimax

Fair

Fair

Fair

Fair

Fair

Good

 

Resource

None

None

None

None

None

Good

 

Spirit

None

None

None

None

None

Good

 

*Status

Poor

Poor

Poor

Poor

Poor

Excel

 

Steadfast Q

Good

Fair

Good

Good

Good

Good

 

Yukon

None

None

None

None

None

Good

1Effectiveness ratings for *atrazine and Princep are not accurate for triazine-resistant lambsquarters, pigweed, and ragweed.

*Restricted-use pesticide; may be purchased and used only by certified applicators or used by someone under the direct supervision of a certified applicator.

†Not for use in Nassau and Suffolk Counties; pesticide labels that indicate “Not for use on Long Island, N.Y.” mean that use is prohibited in Nassau and Suffolk Counties only.

 

Table 3.7.2. Labeled application timings for corn herbicides (shaded cells).

Corn Herbicides

EPP**

PPI**

PRE**

SPK**-2 Leaf VE-V1

EPO** 4–5 Leaf V2-V3

MPO** 6–7 Leaf V4-V5

LPO** 8+ Leaf V6+

Maximum Height Broadcast

*AAtrex/*Atrazine

 

 

 

 

 

 

 

12 in.

Accent Q

 

 

 

 

 

 

 

 

20 in.

Aim

 

 

 

 

 

 

 

V8

Banvel/Clarity

 

 

 

 

 

 

 

36 in.

Basagran

 

 

 

 

 

 

 

 

Basis

 

 

 

 

 

 

 

 

6 in.

*Beacon

 

 

 

 

 

 

 

20 in.

*†Bicep II Magnum

 

 

 

 

 

 

 

5 in.

*†Bicep Lite II Magnum

 

 

 

 

 

 

 

5 in.

Buctril

 

 

 

 

 

 

 

before tassel

*†Bullet

 

 

 

 

 

 

 

5 in.

Callisto

 

 

 

 

 

 

 

30 in.

2,4-D

 

 

 

 

 

 

 

8 in.

*†Dual II Magnum/*†Cinch

 

 

 

 

 

 

 

5 in.

Express

 

 

 

 

 

 

 

 

*†G-Max Lite

 

 

 

 

 

 

 

12 in.

*†Guardsman MAX

 

 

 

 

 

 

 

12 in.

*†Halex GT

 

 

 

 

 

 

 

30 in.

*†Hornet WDG

 

 

 

 

 

 

 

20 in.

Ignite 280

 

 

 

 

 

 

 

24 in

Impact

 

 

 

 

 

 

 

 

Laudis

 

 

 

 

 

 

 

 

Lorox/Linex

 

 

 

 

 

 

 

.

*†Lexar

 

 

 

 

 

 

 

12 in.

*†Lumax

 

 

 

 

 

 

 

 5 in.

*Marksman

 

 

 

 

 

 

 

8 in.

*†Micro-Tech

 

 

 

 

 

 

 

5 in.

NorthStar

 

 

 

 

 

 

 

 

20 in.

Option

 

 

 

 

 

 

 

 

 

V6

*†Outlook

 

 

 

 

 

 

 

12 in.

Permit

 

 

 

 

 

 

 

layby

Princep

 

 

 

 

 

 

 

 

Prowl/Pendimax

 

 

 

 

 

 

 

30 in.

†Python

 

 

 

 

 

 

 

 

1 in.

Resolve Q

 

 

 

 

 

 

 

 

20 in.

Resource

 

 

 

 

 

 

 

V10

Roundup (glyphosate)

 

 

 

 

 

 

 

30 in.

Sencor

 

 

 

 

 

 

 

 

*Shotgun

 

 

 

 

 

 

 

8 in.

Spirit

 

 

 

 

 

 

 

24 in.

*Status

 

 

 

 

 

 

 

36 in.

Steadfast Q

 

 

 

 

 

 

 

 

20 in.

*†Stinger

 

 

 

 

 

 

 

24 in.

Yukon

 

 

 

 

 

 

 

36 in.

*Restricted-use pesticide; may be purchased and used only by certified applicators or used by someone under the direct supervision of a certified applicator

†Not for use in Nassau and Suffolk Counties; pesticide labels that indicate “Not for use on Long Island, N.Y.” mean that use is prohibited in Nassau and Suffolk Counties only.

**EPP=Early Preplant, PPI=Preplant Incorporated, PRE=Preemergence, SPK=Spike, EPO=Early Postemergence, MPO=Mid-Postemergence, LPO=Late Postemergence

 

 

 

Table 3.7.3. Chemical weed control in corn.

Weed Situation

Amount of Product(s) per Acre

Remarks and Limitations

Conventional corn hybrids

PRE Programs Annual grass and broadleaf weeds

3.0–3.75 qt. *†Bullet

GROUP 5 and 15 HERBICIDES • Apply preemergence or early postemergence. If used postemergence, apply before weeds pass the 2-leaf stage and before corn is 5 in. tall. *†Bullet is not for use in Nassau and Suffolk Counties.

 

3 pt. *†G-Max Lite

GROUP 5 and 15 HERBICIDES • Apply preemergence or early postemergence to corn up to 12 in. tall. *†G-Max Lite is not for use in Nassau and Suffolk Counties.

 

1.5 qt. *†Bicep Lite II Magnum or 1.5 qt. *†Cinch ATZ Lite

GROUP 5 and 15 HERBICIDES • Apply preemergence or early postemergence to corn up to 5 in. tall. A lower rate of *†Bicep Lite II Magnum or *†Cinch ATZ Lite should be used on sandy and/or low organic matter soils. *†Bicep Lite II Magnum and *†Cinch ATZ Lite are not for use in Nassau and Suffolk Counties.

 

1.5 qt. *†Bicep Lite II Magnum or 1.5 qt. *†Cinch ATZ Lite
+ 1 qt. Princep 4L

GROUP 5 and 15 HERBICIDES • Preemergence only. Use with heavy infestations of crabgrass or fall panicum. *Atrazine and (or) Princep carryover may injure triazine-sensitive rotational crops. *†Bicep Lite II Magnum and *†Cinch ATZ Lite are not for use in Nassau and Suffolk Counties.

 

2.5–3.0 qt. *†Lumax

GROUP 5, 15 and 27 HERBICIDES • Apply preemergence or early postemergence before corn reaches 5 in. in height. Use 2.5 qt./A if soil organic matter content is less than 3 percent and 3 qt./A if soil organic matter content is 3 percent or greater. The addition of 1 pt./A of *atrazine will improve common ragweed control.. *†Lumax is not for use in Nassau and Suffolk Counties.

 

3.0-3.5 qt.*†Lexar

GROUP 5, 15, AND 27 HERBICIDES • Apply preemergence or early postemergence before corn reaches 12 in. in height. Use 3 qt./A if soil organic matter is less than 3% and 3.5 qt./A if soil organic matter is 3% or greater. *†Lexar provides twice as much *atrazine/A as *†Lumax (see Table 3.7.6 for the amount of *atrazine at labeled rates of each product). This additional *atrazine should improve common ragweed control. *†Lexar is not for use in Nassau and Suffolk Counties.

 

3 pt. Prowl H2O
or 3.6 pt. Prowl 3.3 EC
or 3.6 pt. Pendimax 3.3
+ 1 qt. *Atrazine 4L1

GROUP 3 and 5 HERBICIDES • Apply preemergence. Prowl/Pendimax should not be applied preplant incorporated for corn. Plant corn at least 1 1/2 in. deep in fields with adequate seedbed preparation to provide good coverage of the corn seed. Good choice if velvetleaf or triazine-resistant lambsquarters are problems.

POST Programs
Emerged annual grass and broadleaf weeds

 

1.5 oz. Steadfast Q
+ 4 fl. oz. Banvel
or 4 fl. oz. Clarity

GROUP 2, and 4 HERBICIDES • Apply early postemergence with crop oil concentrate or nonionic surfactant and ammonium nitrogen fertilizer to hybrids with a relative maturity (RM) rating of 77 days or more. For best results, apply when annual weeds are 1-2 in. tall and before corn is 12 in. tall. A good choice if foxtails or fall panicum and annual broadleaf weeds have emerged. Not very effective against crabgrass. Rotational interval is 10 months or longer (depending on soil pH) for alfalfa, clovers, and several other crops. Do not apply Steadfast if corn was treated with Counter 15G (any application method).

 

0.75 fl. oz. Impact
+ 1 pt *Atrazine 4L

GROUP 27 and 5 HERBICIDES • Apply early postemergence with methylated seed oil (MSO) or crop oil concentrate and ammonium nitrogen fertilizer when annual weeds are 1 - 2 in. tall. May be tank mixed with half rates of preemergence herbicides shown above under PRE Programs for added residual weed control. Use COC if tank mixing with Prowl rather than MSO. Rotation interval following Impact application is 3 months for small grains and 9 months for alfalfa, peas, potatoes, and soybeans.

 

3 fl. oz. Laudis
+ 1 pt *Atrazine 4L

GROUP 27 and 5 HERBICIDES • Apply early postemergence with methylated seed oil (MSO) and ammonium nitrogen fertilizer when annual weeds are 1 - 3 in. tall. May be tank mixed with half rates of preemergence herbicides shown above under PRE Programs, except Prowl/Pendimax combinations, for added residual weed control. Rotation interval following Laudis application is 4 months for small grains, 8 months for soybeans, and 10 months for alfalfa, potatoes, and snap beans.

Problem Weed
Quackgrass

22–44 fl. oz. Roundup PowerMax

or 24-48 fl. oz. Durango DMA

or 24-48 fl. oz. Touchdown Total

GROUP 9 HERBICIDES • Apply these or other glyphosate products as a foliar spray in the spring or fall when quackgrass is at least 8 in. tall (4- to 5-leaf stage and actively growing). Fall applications should not be made in fields that have been tilled during the summer or mowed after August 15. Delay tillage for at least 3 days after spraying. The low rates may not provide long-term quackgrass control.

 

1.5 oz. Steadfast Q
or 0.76 oz. *Beacon

GROUP 2 HERBICIDES • Apply postemergence when quackgrass is 4 to 8 in. tall and corn is between 4 and 20 in. A nonionic surfactant or a crop oil concentrate must be used. Do not apply Steadfast Q or *Beacon if corn was treated with Counter 15G (any application method). Rotational intervals for alfalfa and several other crops are 10 months or longer (depending on soil pH) for Steadfast Q and are 8 months for *Beacon.

Problem Weed
Yellow nutsedge, annual grass and broadleaf weeds

1.33–1.67 pt. *†Dual II Magnum + 1.67 qt. *Atrazine 4L1

GROUP 5 and 15 HERBICIDES • Apply preplant-incorporated. Use the high rate of *†Dual II Magnum on heavy (fine-textured) soils. *†Bicep II Magnum can be substituted for this tank mixture. Do not plant spring-seeded small grains or small-seeded legumes and grasses the year following application or injury may occur. *†Dual II Magnum is not for use in Nassau and Suffolk Counties.

Problem Weed
Yellow nutsedge

0.66-1 oz. Permit

GROUP 2 HERBICIDE • Apply postemergence when nutsedge is 2-4 in. tall. A crop oil concentrate or a nonionic surfactant must be used. Rotational interval is 9 months for alfalfa, clovers, and several other crops.

 

4 - 6 oz. Yukon

GROUP 2 and 4 HERBICIDES • Apply postemergence when nutsedge is 2-4 in. tall. A crop oil concentrate or a nonionic surfactant must be used. This pre-mix combination of halosulfuron (the active ingredient in Permit) and dicamba (the active ingredient in Banvel, Clarity, etc.) will provide better control of common lambsquarters, than Permit alone. Rotational interval is 9 months for alfalfa, clovers, and several other crops.

Problem Weed
Velvetleaf

2.5–3.0 qt. *†Lumax

GROUP 5, 15, and 27 HERBICIDES • Apply preemergence or early postemergence before corn reaches 5 in. in height. Use 2.5 qt./A if soil organic matter content is less than 3 percent and 3 qt./A if soil organic matter content is 3 percent or greater. The addition of 1 pt./A of *atrazine will improve common ragweed control. *†Lumax is not for use in Nassau and Suffolk Counties.

 

3.6 pt. Prowl 3.3 EC
or 3.6 pt. Pendimax 3.3
+ 1 qt. *Atrazine 4Ll

GROUP 3 and 5 HERBICIDES • Apply preemergence or early postemergence before corn is 12 in. tall. Do not apply postemergence treatments in liquid fertilizer or following preemergence Prowl applications. Do not apply preplant-incorporated. Plant corn at least 1 1/2 in. deep in fields with adequate seedbed preparation to provide good seed coverage.

 

1.0–1.5 pt. Buctril

GROUP 6 HERBICIDE • Apply early postemergence when velvetleaf is 2–4 in. tall and corn is in the 4- to 6-leaf stage. Buctril may be tank mixed with low rates of *atrazine (1–2 pt./A) to increase activity. Will not control grasses, so should be used with preplant or preemergence herbicide combinations.

 

4-8 fl. oz. Banvel.
or 4-8 fl. oz. Clarity

GROUP 4 HERBICIDES • Apply early postemergence when velvetleaf is 1–2 in. tall. Will not control grasses, so should be applied to fields previously treated with preplant or preemergence herbicides. Do not apply after corn is 30 in. tall.

 

2 oz. *†Hornet WDG
+ 2 fl. oz. Banvel
or 2 fl. oz. Clarity

GROUP 2 and 4 HERBICIDES • Apply early postemergence when weeds are 1–3 in. tall and corn from the spike stage to 20 in. tall. All applications of *†Hornet WDG must include 0.25% (v/v) nonionic surfactant or 1% (v/v) of crop oil concentrate. *†Hornet WDG is not for use in Nassau and Suffolk Counties.

 

0.5 fl. oz. Aim EW

GROUP 14 HERBICIDE • Apply postemergence for velvetleaf up to 18 in. tall. Use a nonionic surfactant at 2 pt./100 gal. (0.25% v/v) of spray solution.

 

4–6 fl. oz. Resource

GROUP 14 HERBICIDE • Use 4 oz./A for velvetleaf up to 5-leaf stage and 6 oz./A for velvetleaf up to 6-leaf stage. Apply with 1 pt./A crop oil concentrate. As a directed spray using drop nozzles, 8 oz./A will control velvetleaf up to 10-leaf stage.

Problem Weeds

Triazine-resistant common lambs-quarters or smooth pigweed

2.5–3.0 qt. *†Lumax

GROUP 5, 15, and 27 HERBICIDES • Apply preemergence or early postemergence before corn reaches 5 in. in height. Use 2.5 qt./A if soil organic matter content is less than 3 percent and 3 qt./A if soil organic matter content is 3 percent or greater. The addition of 1 pt./A of *atrazine will improve common ragweed control. *†Lumax is not for use in Nassau and Suffolk Counties.

 

3.6 pt. Prowl 3.3 EC
or 3.6 pt. Pendimax 3.3
 + 1 qt. *Atrazine 4L1

GROUP 3 and 5 HERBICIDES • Apply preemergence or early postemergence until corn is 12 in. tall. Do not apply postemergence treatments in liquid fertilizer or following preemergence Prowl applications. Do not apply preplant-incorporated. Plant corn at least 1 1/2 in. deep in fields with adequate seedbed preparation to provide good seed coverage.

Problem Weeds
Triazine-resistant common lambs-quarters, smooth pig-weed, or common ragweed

4-8 fl. oz. Banvel
or 4-8 fl. oz. Clarity

GROUP 4 HERBICIDE • Apply early postemergence when weeds are 1–2 in. tall. Will not control grasses, so should be applied to fields previously treated with preplant or preemergence herbicides. Do not apply after corn is 30 in. tall.

2 oz. *†Hornet WDG
+ 2 fl. oz. Banvel
or 2 fl. oz. Clarity

GROUP 2 and 4 HERBICIDES • Apply early postemergence when weeds are 1–3 in. tall and corn from the spike stage to 20 in. tall. All applications of *†Hornet WDG must include 0.25% (v/v) nonionic surfactant or 1% (v/v) of crop oil concentrate. *†Hornet WDG is not for use in Nassau and Suffolk Counties.

Problem Weeds

Triazine-resistant common lambs-quarters or common ragweed

1–1.5 pt. Buctril

GROUP 6 HERBICIDE • Apply early postemergence when weeds are 2–4 in. tall and corn is in the 3- to 8-leaf stage. Will not control grasses, so should be used with preplant or preemergence combinations.

Problem Weeds

Triazine-resistant common lambs-quarters or smooth pigweed

3 fl. oz. Callisto

GROUP 27 HERBICIDE • Apply postemergence to weeds less than 5 in. tall. Add crop oil concentrate to spray solution at 1 gal./100 gal. (1.0% v/v) and 28% UAN at 2.5% (v/v) or AMS (ammonium sulfate) at 8.5 lb./100 gal. Corn may be treated up to 30 in. tall or up to the 8-leaf stage.

Problem Weeds

Triazine-resistant smooth pigweed only

3-3.75 qt.*† Bullet

GROUP 5 and 15 HERBICIDES • Apply preemergence. *†Bullet is not for use in Nassau and Suffolk Counties.

3 pt. *†G-Max Lite

GROUP 5 and 15 HERBICIDES • Apply preemergence or early postemergence to corn up to 12 in. tall. *†G-Max Lite is not for use in Nassau and Suffolk Counties.

 

1.5 qt. *†Bicep Lite II Magnum
or 1.5 qt. *†Cinch ATZ Lite

GROUP 5 and 15 HERBICIDES • Apply preemergence. A lower rate of Bicep Lite II Magnum should be used on sandy and/or low organic matter soils. *†Bicep Lite II Magnum and *†Cinch ATZ Lite are not for use in Nassau and Suffolk Counties.

Problem Weed
Triazine-resistant common groundsel

1–1.5 pt. Buctril

GROUP 6 HERBICIDE • Apply early postemergence when weeds are 2–4 in. tall and corn is in the 3- to 8-leaf stage. Will not control grasses, so should be used with preplant or preemergence combinations.

Problem Weeds
Broadleaf perennials: milkweed, field bindweed, hedge bindweed, hemp dogbane, horsenettle, Jerusalem artichoke

8 fl. oz. Banvel
or 8 fl. oz. Clarity

GROUP 4 HERBICIDES • Apply postemergence when weeds are at, or near the bud stage. Banvel will not control grasses, so should be applied to fields previously treated with preplant or preemergence herbicide combinations. This treatment may follow early postemergence Banvel applications used for broadleaf annual weeds and should be repeated 2 or 3 successive seasons for best results. Do not apply after corn is 30 in. tall.

Glyphosate-resistant (Roundup Ready) corn hybrids

Emerged grass and broadleaf weeds

22 fl. oz. Roundup PowerMax
or 24 fl. oz. Durango DMA
or 24 fl oz. Touchdown Total

GROUP 9 HERBICIDES • For use with glyphosate-resistant (Roundup Ready) corn only. Apply these or other glyphosate products early postemergence in a tank mix with 50 percent of the labeled rate of an appropriate residual premix or tank-mix combination when weeds are 2-4 in. tall. See above under PRE Programs for conventional corn hybrids for examples of residual premix or tank-mix combinations.

 

3.6-4 pt *†Halex GT

GROUP 9, 15, and 27 HERBICIDES • Apply early postemergence when weeds are 2-4 in. tall until corn is 30 in. tall. *†Halex GT must be applied with a non-ionic surfactant and ammonium sulfate. *†Halex GT is not for use in Nassau and Suffolk Counties.

 

22 fl. oz. Roundup PowerMax
or 24 fl. oz. Durango DMA
or 24 fl oz. Touchdown Total
+ 1.25 oz. Resolve Q

GROUP 2 and 9 HERBICIDES • Apply Resolve Q with these or other glyphosate products early postemergence when weeds are 1-2 in. tall. If the glyphosate product contains a built-in adjuvant system, no additional surfactant is needed. Rotation interval followimg Resolve Q application is 3 months for winter cereals and 10 months for alfalfa, soybeans, and many other crops.

Problem Weed

Quackgrass
Pre-plant approach

22–44 fl. oz. Roundup PowerMax

or 24-48 fl. oz, Durango DMA

or 24-48 fl. oz. Touchdown Total

GROUP 9 HERBICIDES • Apply these or other glyphosate products as pre-plant foliar sprays in the spring or fall when quackgrass is at least 8 in. tall (4- to 5-leaf stage and actively growing). Fall applications should not be made in fields that have been tilled during the summer or mowed after August 15. Delay tillage for at least 3 days after spraying. The low rates may not provide long-term quackgrass control.

Problem Weed

Wirestem muhly

22 fl. oz. Roundup PowerMax
or 24 fl. oz. Durango DMA
or 24 fl. oz. Touchdown Total

GROUP 9 HERBICIDES • For use with glyphosate-resistant (Roundup Ready) corn only. Apply 50 percent of the labeled rate of an appropriate residual herbicide program preemergence to suppress annual weeds. Follow with a postemergence application of glyphosate when wirestem muhly is 8 in. tall and corn is no more than 30 in. tall.

Problem Weed

Yellow nutsedge, emerged grass and broadleaf weeds

22 fl. oz. Roundup PowerMax
or 24 fl. oz. Durango DMA
or 24 fl. oz. Touchdown Total
+ 0.33-0.66 oz. Permit
or 2-4 oz. Yukon

GROUP 2, 4, and 9 HERBICIDES • Apply postemergence when nutsedge and other weeds are 2 – 4 in. tall.

Liberty Link Corn Hybrids

Emerged annual grass and broadleaf weeds

22 fl. oz. Ignite 280 SL
+ 1.5 pt. *Atrazine 4L 

GROUP 5 and 10 HERBICIDES • For use with Liberty Link corn only. Apply early postemergence when annual weeds are 2 to 4 in. tall. Ignite 280 SL must be applied between dawn and 2 hours before sunset with a spray grade AMS (ammonium sulfate) at 3 lb./A. Tank mixes with reduced (half) rates of other residual herbicides may be desirable depending on weed spectrum.

1One qt. of *atrazine 4L is equivalent to 1.11 lb. *AAtrex 90.

*Restricted-use pesticide; may be purchased and used only by certified applicators or used by someone under the direct supervision of a certified applicator.

†Not for use in Nassau and Suffolk Counties; pesticide labels that indicate “Not for use on Long Island, N.Y.” mean that use is prohibited in Nassau and Suffolk Counties only.

• Refer to Section 3.7.3 for information on herbicide resistance management and site of action groups.

 

 

 

Table 3.7.4. Burndown for zone/no-tillage corn.

Weed Situation

Amount of Product(s) per Acre

Remarks and Limitations

Legume-grass sod control initiated in fall

44 fl. oz. Roundup PowerMax

or 48 fl. oz. Durango DMA

or 48 fl. oz. Touchdown Total

+ 1 pt. 3.8 lb./gal. 2,4-D

GROUP 4 and 9 HERBICIDES • Apply these or other glyphosate products plus 2,4-D as a foliar spray in fall when grasses are at least 8 in. tall (4- to 5-leaf stage) and actively growing. A reduced rate of glyphosate or an application of *Gramoxone Inteon may be needed to enhance burndown of germinating weeds before or at planting in the spring. If alfalfa, dandelions, or other perennial broadleaf weeds persist, apply 1/2 pt./A Banvel or Clarity postemergence before corn is 30 in. tall.

Legume-grass sod control at planting

44 fl. oz. Roundup PowerMax

or 48 fl. oz. Durango DMA

or 48 fl. oz. Touchdown Total

+ 1 pt. 3.8 lb./gal. 2,4-D

GROUP 4 and 9 HERBICIDES • Apply these or other glyphosate tank mixes when grasses are at least 8 in. tall (4- to 5-leaf stage) at least 7 days before planting. May be tank mixed with residual herbicides registered for early preplant use. If alfalfa, dandelions, or other perennial broadleaf weeds persist, apply 1/2 pt./A Banvel or Clarity postemergence before corn is 30 in. tall.

Previously cropped with cover crop of rye, barley, wheat, or ryegrass

20 fl. oz. Roundup PowerMax or

24 fl. oz. Durango DMA or 24 fl. oz. Touchdown Total

or 3-4 pt. *Gramoxone Inteon

GROUP 9 or 22 HERBICIDES • Apply from 7 days before planting up to and at the time of planting. When using *Gramoxone Inteon for burndown, add a nonionic surfactant to the spray tank to enhance penetration and total kill.

Previously cropped with no cover crop

 

Same as with cover crop if significant weed cover is present at planting. If weed cover is minimal, a burndown herbicide may not be needed depending on what other herbicides are being applied.

Problem Weed
Dandelion

22 fl. oz. Roundup PowerMax or

24 fl. oz. Durango DMA or 24 fl. oz. Touchdown Total + 1 pt. 3.8 lb./gal. 2,4-D LVE

GROUP 4 and 9 HERBICIDES • Apply in fall or in spring prior to planting corn. Addition of crop oil concentrate may enhance dandelion control.

 

0.5 oz. Express

+ 1 pt. 3.8 lb./gal. 2,4-D LVE

GROUP 2 and 4 HERBICIDES • Apply in fall to actively growing dandelions or in spring at least 14 days before planting corn. Add crop oil concentrate according to label.

*Restricted-use pesticide; may be purchased and used only by certified applicators or used by someone under the direct supervision of a certified applicator.

• Refer to Section 3.7.3 for information on herbicide resistance management and site of action groups.

 

 

Table 3.7.5. Components of some prepackaged corn herbicide mixtures.

Product

Formulation

Active Ingredients of Each Herbicide per Gallon

*†Bicep II Magnum/*†Cinch ATZ

5.5L

2.4 lb.*†Dual II Magnum

+

3.1 lb. *atrazine

*†Bicep Lite II Magnum/*†Cinch ATZ Lite

6L

3.33 lb.*†Dual II Magnum

+

2.67 lb. *atrazine

*†Bullet

4L

2.5 lb. *†Micro-Tech

+

1.5 lb. *atrazine

*†G-Max Lite

5L

2.25 lb. *†Outlook

+

2.75 lb. *atrazine

*†Guardsman Max

5L

1.7 lb. *†Outlook

+

3.3 lb. *atrazine

*†Lexar

3.7L

1.74 lb. *†Dual II Magnum

+

0.224 lb. Callisto +1.7 lb. *atrazine

*†Lumax

3.94L

2.68 lb. *†Dual II Magnum

+

0.268 lb. Callisto + 1 lb. *atrazine

*Marksman

3.2L

1.1 lb. dicamba

+

2.1 lb. *atrazine

*Shotgun

3.25L

1.0 lb. 2,4-D

+

2.25 lb. *atrazine

*Restricted-use pesticide; may be purchased and used only by certified applicators or used by someone under the direct supervision of a certified applicator.

†Not for use on Long Island, N.Y. not for use in Nassau and Suffolk Counties; pesticide labels that indicate “Not for use on Long Island, N.Y.” mean that use is prohibited in Nassau and Suffolk Counties only.

 

Table 3.7.6. Pounds active ingredient per acre (lb. ai/A) of *atrazine with common labeled rates of herbicide premixes.

Product

Formulation

Amount of Product per Acre

lb. ai/A of *Atrazine

*†Bicep II Magnum or

5.5L

1.6 qt.

1.24

*† Cinch ATZ

 

2.1 qt.

1.63

*†Bicep Lite II Magnum or

6L

1.1 qt.

0.73

*† Cinch ATZ Lite

 

1.5 qt.

1

*†Bullet

4L

3.75 qt.

1.41

 

 

4.5 qt.

1.68

*†G-Max Lite

5L

2.5 pt.

0.86

 

 

3.0 pt.

1

*†Guardsman Max

5L

3.0 pt.

1.24

 

 

4.0 pt.

1.65

*†Lexar

3.7L

3.0 qt.

1.31

 

 

3.5 qt.

1.52

*†Lumax

3.94L

2.5 qt.

0.63

 

 

3.0 qt.

0.75

*Marksman

3.2L

2.0 pt.

0.52

 

 

3.5 pt.

0.92

*Shotgun

3.25L

2.0 pt.

0.56

 

 

3.0 pt.

0.84

*Restricted-use pesticide; may be purchased and used only by certified applicators or used by someone under the direct supervision of a certified applicator.

†Not for use in Nassau and Suffolk Counties; pesticide labels that indicate “Not for use on Long Island, N.Y.” mean that use is prohibited in Nassau and Suffolk Counties only.