Weed Control in No-Till Systems         
Revised by Glenn Nice, Bill Johnson, T. Bauman                 

A no-till planted field does not have to mean a field full of weeds. No-tillage systems use herbicide applications instead of cultivation for weed control. A greater reliance on herbicides requires attention to detail--types of weeds, weather trends, cropping patterns, soil type--in order to control weed populations without adversely affecting the environment. The first few years of no-tillage may require higher herbicide inputs. However, many long-term growers claim once no-till is established, herbicide costs generally decrease and become competitive with conventional systems.

Successful weed control in no-tillage requires:

  • accurately identifying weeds
  • proper timing of herbicide treatments
  • scouting and monitoring fields for problem areas
  • spot spraying herbaceous and woody perennials
  • keeping fence rows and field borders free of aggressive weeds
  • assuring even distribution of crop residue after harvest

Shift in Weed Species

Without deep tillage weed seeds stay near the soil surface instead of being buried too deep for germination. Small-seeded broadleaf weeds and annual grasses can germinate under crop residue as shown in Figure 1. Large-seeded weeds, such as velvetleaf and common cocklebur, need deeper soil placement to germinate. With continued no-tillage large-seeded weed populations tend to decline. Both simple perennial and creeping perennial weeds multiply in a no-tillage system. Creeping perennials also tend to be a problem in conventional tillage systems although tillage controls simple perennials. Table 1 lists the weeds commonly found in no-till planted fields (see page 2).

Weed Control Strategies in No-tillage

Early preplant

For the best results apply early preplant herbicide treatments before germination of summer annual weeds. The timing of these treatments range from ten to 45 days prior to planting of the crop, see Tables 2 and 3. Applying herbicides early in the season, when rains are more frequent, insures activation of the herbicides. Early application also helps spread out the spring work load. With timely herbicide applications, the fields will be free of weeds at planting, eliminating the need for a burndown treatment. Early killing of weeds also discourages insects attracted to weedy fields, such as black cutworm moths.

dandelion
Figure 1. An uneven covering of residue can interfere with the effectiveness of herbicide applications. Large clumps of residue shield weeds and grasses from herbicides. 
Weeds in no-tilled fields tend to germinate throughout the season. Maintain season-long weed control with early pre-plant treatments of "full season" residual herbicides or split treatments of herbicides with medium longevity. Split applications often include applying 1/3 of the labeled herbicide rate early and the remaining 2/3 at planting. Many early preplant herbicides have burndown activity on small weeds (1" to 3"). Adding a crop oil or surfactant to the herbicide mix improves their control. Weeds greater than 3", such as winter or early summer annuals, may be present at the time of early preplant applications. Abundant weed growth may require a burndown herbicide, such as glyphosate + 2,4-D, paraquat, or 2,4-D.
Table 1. Common Weeds in No-till Systems

Annual Weeds
Summer Annuals
Simple Perennials
Creeping Perennials
Common chickweed
Common lambsquarteres
Common pokeweed
Canada thistle
Henbit
Pigweed
Common dandelion
Hemp dogbane
Purple deadnettle
black nightshade
Wild four'o clock
Jerusalem artichoke
Cressleaf groundsel
Common ragweed
Curly dock
Bindweeds
Downy brome
Giant ragweed
Common milkweed
Wild mustard
Annual smartweed
Biennials
Honeyvine milkweed
Shepherdspurse
horseweed/marestail
Wild carrot
Trumpetcreeper
Prickly lettuce
Foxtail
Common mullien
Bigroot morningglory
horseweed/marestail
Fall panicum
Poison hemlock
Horsenettle
Crabgrass
Common burdock
Ground cherry
Swamp smartweed
     
Yellow nutsedge
     
Johnsongrass
     
Quackgrass
     
Wirestem muhly
     
Trees

Weeds in no-tilled fields tend to germinate throughout the season. Maintain season-long weed control with early pre-plant treatments of "full season" residual herbicides or split treatments of herbicides with medium longevity. Split applications often include applying 1/3 of the labeled herbicide rate early and the remaining 2/3 at planting. Many early preplant herbicides have burndown activity on small weeds (1" to 3"). Adding a crop oil or surfactant to the herbicide mix improves their control. Weeds greater than 3", such as winter or early summer annuals, may be present at the time of early preplant applications. Abundant weed growth may require a burndown herbicide, such as glyphosate + 2,4-D, paraquat, or 2,4-D.

Burndown

Burndown herbicides control emerged weeds before or just after planting, but prior to crop emergence. These herbicides can be combined with early preplant or preemergence treatments. Paraquat (e.g. Gramoxone Inteon) works well in combination with residual herbicides. A tank mix of glyphosate (eg. Roundup Weathermax) and 2,4-D broadens the spectrum of weed control. The weed species present, size, life cycle, and herbicide efficacy determines what and how much herbicide to apply.

Preemergence

The success of preemergence herbicide treatments depends on rainfall to activate the herbicide soon after spraying. Without moisture, herbicide performance suffers. Herbicides that are soil-applied after planting are often preferred over treatment prior to planting. Planter row-cleaners or "trash-whippers" can move herbicide-treated soil from the row to the row middles, creating weed problems in the untreated zone.
Two types of preemergence herbicide programs are common in no-tillage:

  1. a full season program--where herbicides control weeds throughout most of the growing season, or
  2. a short residual program--where the crop shades out later germinating weeds. Postemergence treatments may be necessary for weed escapes.
Table 2. Early Preplant Herbicides for Corn

Herbicide Days Before Planting
Atrazine 30-45 (split applications, do not exceed total maximum allowd rates); less than 30; less than 14 on coarse soils.
Balance Pro, Epic, Radius 30 in a pre + post program (split with 60% first followed by 40% or single); 21 days
Banvel, Clarity, Marksman  
Dual II Magnum, Outlook, Harness, Micro-Tech 30-45 (split); less than 30 (split or single)
Gaurdsman Max, Harness Xtra 30-45 (split); less than 30 (split or single) up to 30
Lariat Less than 30 (single); less than 45 (split)
Pursuit (imi corn hybrids only) May be applied EPP (number of days not mentioned in label)

*These herbicides will burndown small (1-3") broadleaf weeds. Add crop oil or surfactant for improved control. If weeds are smaller than 3" or one of the early preplant (EPP) treatments are applied then add a burndown herbicide such as Gramoxone Inteon, glyphosate (Roundup Weathermax, Touchdown, etc) 2,4-D according to label directions
**Split applications = 2/3 rate EPP and 1/3 at planting. Single applicaitons = total rate applied EPP

Postemergence

Postemergence treatments work well in a no-tillage system where no soil-applied treatments are planned and also in fields where perennial weeds, such as johnsongrass or Canada thistle are a problem. Soil type or the amount of crop residue present generally does not affect postemergence treatments. Postemergent application does depend on proper timing and correct identification of the target weeds. Successful total postemergence programs occur in fields that are weed-free when planted.

No-tilling into sod

No-tilling in to old hay fields, set-aside, or idle land presents a special challenge. To get a good kill of both grass and legume sods takes advanced planning. Generally products like glyphosate (e.g. Roundup) easily kill grass sod in the fall. Spring applications require higher rates of Roundup than fall applications for better kill. Spring treatments of Gramoxone Inteon plus atrazine can provide good control of a mixed stand of grass and legumes before planting corn. The sod needs to be actively growing with sufficient growth for translocative herbicides, such as glyphosate, dicamba (e.g. Banvel) and 2,4-D to be effective. Sod must be at a certain height and environmental condition before it is sprayed. The herbicide application may delay planting. Corn planted into a legume sod has more control options than for soybeans. Growth regulator herbicides, such as 2,4-D and dicamba, used postemergence in corn control escaped legumes, but not in soybeans.

Crop competition and Mulches

Quick canopy closure provides shade and controls late germinating weeds. However, recent research done by Bill Johnson in Indiana fields with common lambsquarters suggested 80% of common lambsquarter below the canopy still produced seed.  Poor crop stands, wide rows, and limited shoot growth result in weedy crops. Without cultivation crop competition becomes an important segment of weed control in no-tillage. Another form of weed control often utilized in no-tillage systems is the establishment of a cover crop prior to planting corn or soybeans. After killing the cover crop with nonselective herbicides the resulting dead mulch serves as a "barrier" to several kinds of small-seeded weeds. Rye and wheat seeded in the fall are the two most common types of cover crops (Figure 2). Not only does the dead rye or wheat straw help smother emerging weed seedlings, but many researchers report the presence of allelopathic chemicals leached from the straw suppress weeds.

Perennial Weeds in No-tillage

Both simple and creeping perennial weeds can become a problem in no-tillage systems. Simple perennials produce a shoot annually from a main taproot, like dandelion. Simple perennials rarely survive in full-till systems. Creeping perennials, such as Canada thistle, reproduce by underground vegetative structures that provide these weeds with both competitive and survival advantages. Creeping roots, rhizomes, and tubers store food and provide numerous buds capable of generating new plants. Creeping perennials can be a problem in both conventional tillage and no-tillage systems.

Perennial weeds, both grasses and broadleaves, can be difficult to control with herbicides in a cropping system. Herbicide rates used in corn and soybeans are not high enough to provide good control of the root system of most perennial broadleaf weeds. Translocated herbicides must be applied at the proper stage of weed growth for optimum control. Generally, perennials effectively move the herbicide into their root system when sprayed prior to full bloom in the spring or when new growth appears in the fall.
Table 3. Early Preplant Herbicides for Soybeans

Herbicide Days Before Planting
Command 3ME Prior to frield green-up and before April 1
Canopy DF, Lorox Plus Up to 30
Canopy EX At least 45
Dual II Magnum 30-45 (split); less than 30 (split or single)
Outlook, Prowl up to 45
Scepter, Lexone 0-30

*These herbicides will burndown small (1"-3") broadleaf weeds. Add crop oil or surfactant for improved control. If weeds are taller than 3" or one of the other EPP treatments are applied then add a burndown herbicide such as Gramoxone Inteon, glyphosate (Roundup Weathermax, Touchdown, etc.), or 2,4-D according to label directions.
**Split applications = 2/3 of labeled rate EPP and 1/3 rate at planting.

For broadleaf perennial control in corn, the use of growth regulator herbicides such as 2,4-D, dicamba, and clopyralid (e.g. Stinger) give "top-kill" as well as provide some control of the root system. Some perennial grass species can be controlled with nicosulfuron (e.g. Accent), and primisulfuron (e.g. Beacon)

Increasing the crop competition to weeds by narrowing the rows and using a postemergence herbicide provide some control of broadleaf perennial weeds in soybeans. Several grass-specific herbicides labeled for soybeans work on perennial, weedy grass species. With any herbicide program, complete control of an entire perennial root system is unlikely with one herbicide application. Follow-up applications the next season(s) are necessary to achieve the desired level of control. Controlling perennial weeds in no-till systems takes persistence.

Controlling perennial weeds with herbicides often calls for special application methods

  • Use wipe-on applicators to apply nonselective translocated herbicides, such as glyphosate (e.g. Roundup Weathermax) to weeds taller than the crop
  • Spot treat to control or suppress perennials prior to planting, in the crop, and at preharvest.
  • Monitor fences rows, field borders, and other non-crop areas. Spray perennial weeds that can spread into fields.
  • Remove by hand simple perennial weed such as pokeweed and curly dock. A large portion of the root or crown must be removed.

Herbicide Tolerant Crops

Crops have now been developed that are resistant or highly tolerant to certain herbicides. Examples of herbicide tolerant crops include Pursuit tolerant (imi) corn, STS soybeans, Roundup Ready soybeans, Poast Compatible corn, and Liberty Link corn and in the next couple of years dicamba tolerant. These special crops provide an option for controlling "hard-to-control" weeds in no-tillage systems. For example, Synchrony STS, a premix of Classic and Pinnacle, provides good top-kill of common milkweed. Roundup Ready soybeans, corn, and alfalfa allows the use of glyphosate products (Roundup Weathermax, Touchdown, etc), a non-selective herbicide, to be applied postemergence to the crop and weeds. Higher labeled use rates and split applications of Roundup will help to control various perennial weeds in no-till soybeans that have been missed with standard herbicide programs. Contact a local seed dealer for more information.

Summary

Changes in tillage influence weed populations. Annual grasses, small-seeded broadleaves, and perennial weeds become more prevalent with no-tillage - while large-seeded broadleaves decline over time. Correct identification of weeds and their life cycles are essential when selecting the proper herbicides for their control. Without tillage, dependency on herbicides to control weeds increases. Preplant herbicide treatments, with or without burndown herbicides, must provide a weed-free field at planting and several days beyond. Early weed control allows the crop to become established without weed competition. Control grass or legume sods. In the fall before planting a crop the following spring. For optimum control, treat perennial weeds prior to flowering or when new growth shows in the fall.

For more information

The following table--Problem Weeds in No-till--recommends herbicide treatments to control specific weeds. For more information on weed control in cropping systems, refer to "Weed Control Guidelines for Indiana", WS-16, or the Purdue University "Herbicide Selector" computer program. Both can be obtained from your county Purdue Cooperative Extension office.

References

"Weeds of the North Central States," NCR-281. University of Illinois.
"2007 Weed Control Guide for Ohio and Indiana," WS-16. Purdue University and The Ohio State University.

Problem Weeds In No-Till (For weed response tables and more information on herbicides see the Weed Control Guide for Ohio and Indiana [WS-16], www.btny.purdue.edu/Pubs/WS/WS-16/

Weed Crop Herbicide Remarks*

Annuals - apply herbicide to weeds that are small and actively growing
Horseweed/ marestail (*ALS, triazine, glyphosate resistance in region) Corn / Soybean glyphosate (0.1 lb ae) +
2,4-D (1 pt/A)
BURNDOWN or FALL: Glyphosate + 2,4-D treatment with a nonionic surfactant 0.5% v/v in 10 gallons of water per acre when the weeds are 6" or less in height. Read specific glyphosate product’s label on whether additional surfactant is allowed. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. If the 2 pt/A rate is used then wait 30 days before planting soybean and 14 days for corn.
    Gramoxone Inteon (2-4 pt/A) + 2,4-D (1 pt/A) BURNDOWN: apply to horseweed while in the rosette stage.
  Corn Banvel / Clarity / Sterling
(1 pt/A)
POST: use 0.5 pt/A on coarse soils and soils with less than 2% organic matter. Apply to horseweed that is small and actively growing. Apply from spike to 8" corn, use 0.5 pt/A on corn that is 8" to 36" or 15 days from tassle. COC, UAN, or AMS can be added to increase postemergence control.
    Atrazine (1 lb ai/A) + 2,4-D (1-2 pt/A) or Banvel (1 pt/A) BURNDOWN: This treatment will also give residual control. Use 0.5 pt/A on coarse soils and soils with less than 2% organic matter.
    Atrazine and/or 2,4-D or Banvel (label rates) BURNDOWN: This treatment will also give residual control.
  Soybean Gramoxone Inteon + Sencor / Lexone (Label rates) BURNDOWN: apply when weeds are very small and actively growing.
    Canopy (4 to 7 oz/A - soil and pH dependent) + 2,4-D (1 pt/A) BURNDOWN: apply when weeds are less than 3" tall. Add a COC to the spray mix. When using the 2,4-D at 1 pt, wait 7 days before planting soybean.
    FirstRate (0.3 oz/A) POST: can be applied up to 50% bloom when horseweed is no larger than 6 inch. Can be tank mixed with glyphosate.
    glyhosate (1 lb ae/A) + 2,4-D (1 pt/A) + FirstRate BURNDOWN: Apply to horseweed that are 6" or smaller. Wait 7 days before planting soybean.
  Roundup Ready Corn/Soybean glyphosate ( 1.1 lb ae/A) POST: apply before soybean are 50% bloomed and corn is in the v8 stage (30" tall). Apply from emergence to V8 (30") RR corn and from emergence through flowering in RR soybean. There are glyphosate resistant horseweed populations in the Mid-west.
  Roundup Ready Soybean glyphosate (1.1 lb ae/A) + FirstRate (0.3 oz/A) or Classic (0.25-0.33 oz/A) POST: apply after first trifoliate. Read glyphosate label on whether or not to use COC or NIS, some glyphosate labels will not allow the addition of surfactants.
       

Cressleaf groundsel (butterweed) Corn / Soybean glyphosate (0.75 lb ae/A) + 2,4-D (1 pt/A) FALL or BURNDOWN: apply in the rosette stage. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean.
    glyphosate (1.5 lb ae/A) + 2,4-D (1 pt/A) BURNDOWN: application before planting to weeds in the rosette stage or shortly after bolting. 2,4-D alone does not effectively control. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean.
  Corn 2,4-D (1 pt/A) + Gramoxone Inteon (3 pt/A) + atrazine (1 lb ai/A) BURNDOWN: apply in the rosette stage. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. Add a COC to improve control
  Soybeans Canopy EX (1.1 oz/A) + 2,4-D (1 pt/A) FALL or BURNDOWN: apply to weeds in the rosette stage. Can be applied 7 days before planting. Add a COC to improve control. Higher rates of Canopy EX can be applied to medium and fine textured soil if composite soil pH is 7 or less.
    Lorox (0.5 to 1.5 lb/A) + Sencor (0.5 to 0.75 lb/A) PRE: rates are dependent on soil texture and organic matter. Apply to cressleaf groundsel up to 6 inches.
    2,4-D (1 pt/A) + Gramoxone Inteon (3 pt/A) + Sencor DF (2/3 to 1 lb/A) BURNDOWN: When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. Add a COC or NIS to improve control. Some soybean varieties may be sensitive to Sencor, consult your seed dealer before applying.
       

Prickly lettuce Corn / Soybean glyphosate (0.75 lb ae/A) + 2,4-D (1 or 2 pt/A) BURNDOWN: apply the glyphosate + 2,4-D treatment in 10 gallons of water per acre when the weed is 6" or less tall. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. If the 2 pt/A rate is used then wait 30 days before planting soybean and 14 days for corn.
  Corn Atrazine (1 lb ai/A) + Banvel (0.5 to 1 pt/A) Apply as a burndown treatment before planting to weeds that are less than 2" tall. Add a COC with the atrazine treatments. Use the 0.5 pt on coarse soils.
    Balance Pro (1.5 to 3 fl oz/A) + atrazine (1 lb ai/A) BURNDOWN or PRE: apply with COC and fertilizer to maximize burndown activity. Balance Pro rates are dependent on soil texture and organic matter. Plant at lease 1.5 inches deep.
    Simazine 4L (1 qt/A) + 2,4-D (1 or 2 pt/A) + NIS (0.5% v/v) FALL: apply after harvest but before ground freezes.
  Soybean Canopy, Lorox Plus, Sencor / Lexone (labeled rates) Apply before planting as a burndown treatment when weeds are less than 3" tall. Add a COC to the spray mix.
  Roundup Ready Corn/Soybean glyphosate (0.5 to 0.75 lb ae/A) POST: apply when prickly lettuce is no more than 4 (0.5 lb ae/A) to 12" (0.75 lb oz/A). Apply from emergence to V8 (30") RR corn and from emergence through flowering in RR soybean.
       

Mustards Corn / Soybean glyphosate (0.75 lb ae/A) + 2,4-D (1 pt/A or 2 pt/A) FALL or BURNDOWN: apply with a nonionic surfactant (0.5% v/v) in 10 gallons of water per acre when the weeds are 6" or less tall. For the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. If the 2 pt/A rate is used then wait 30 days before planting soybean and 14 days for corn.
    Gramoxone Inteon (1.5-4 pt/A, depending on size) BURNDOWN: Apply in a minimum of 20 GPA.
  Corn Atrazine (2 lb ai/A) + COC (0.5% v/v) BURNDOWN: apply before planting when weeds are 3" or less.
    Lumax (2.5-3 qt) or Lexar (3-3.5 qt) PRE: apply to weeds 3" (Lumax) or 5 (Lexar) inches tall. A nonionic surfactant may be added. Do not apply POST to corn that has been treated with organophosphate insecticides.
    Autumn (0.3 oz/A) or Simazine 4L (1 qt/A) or Basis (1/3 - 1/2 oz/A) + 2,4-D (1 or 2 pt/A) + NIS (0.5% v/v) for simazine and COC (1% v/v) for Basis FALL: apply after harvest but before ground freezes. Do not apply Basis to coarse soils with less than 1% organic matter. Use 0.5% v/v nonionic surfactant when using simazine, or 1% v/v COC when using Basis or Autumn. Add 1.5 to 3 lb/A AMS when using Autumn.
  Soybean Canopy DF (2.25 - 7 oz/A fall, 4 - 7 oz/A spring) or Canopy EX + 2,4-D (0.5 pt/A) FALL or BURNDOWN: rate is dependent on soil pH and organic matter. Apply to 1 to 3" weeds. Canopy can be applied up to 45 days before planting. NIS (0.25% v/v) or COC (1% v/v). Canopy EX can be applied 7 (1.1 oz/A) or 14 (> 1.1 oz/A) days before planting soybean. Wait at least 7 days before planting with they use of 2,4-D at this rate.
       

Perennials - apply translocative herbicides to bloom and/or on fall regrowth
Bindweed Corn 2,4-D ester (2 pt/A before planting or 0.75-1 pt/A after crop emergence) or 2,4-D amine (1-1.5 pt/A) PRE or POST: apply to postemergence bindweed in spring when leaves are fully expanded or apply pre-harvest after brown silk stage in corn. The ester formulation is preferred. Use drop nozzles when corn is over 8" tall. For the 2,4-D at 1 pt, wait 7 days before planting corn. If the 2 pt/A rate is used then wait 14 days before planting corn.
    Distinct (4 to 6 oz/A) POST: rate is size dependent, 6 oz/A can be applied on 4 to 10 inch corn and 4 oz/A can be applied on 10 to 24 inch corn. Applications above 8 inch corn increase risk of injury. Add 0.25% v/v noniconic surfactant + 5 lb/100 gal AMS.
    Banvel / Clarity (0.5-1 pt/A) Use the 0.5 pt rate of Banvel or Clarity postemergence on sandy soils. On corn between 8 and 36" use Banvel at 0.5 pt/A. Risk of injury increases when corn is greater than 8 to 10 inches tall.
    NorthStar (5 oz/A) or Yukon (6 - 8 oz/A) POST: apply when bindweed is less than 6 inches long. Apply when corn is 4 to 20 inches tall and use drop nozzles when corn is 20 to 36 inches. Applications must stop at least 15 days before tassel emergence. Add 0.25 - 0.5% v/v nonionic surfactant or 1% v/v COC + 2 - 4 lb/A AMS
  Corn (Clearfield) Lightning (1.28 oz/A) + Distinct (4 - 6 oz/A) POST: apply to 1 - 3 inch bindweed. Rate is size dependent, 6 oz/A can be applied on 4 to 10 inch corn and 4 oz/A can be applied on 10 to 24 inch corn. Applications above 8 inch corn increase risk of injury. Add 1% v/v COC + 5 lb/100 gal AMS.
  Soybeans Ultra Blazer (2 pt/A), Cobra (12.5 oz/A), Reflex (1.25 pt/A), FlexStar (1 - 1.5 pt/A) or with Basagran (1 - 2 pt/A) POST: Vines may be suppressed by these postemergence applications. Apply when vines are 12 to 18 inches long. Control can be improved by adding 2 fluid ounces/a of 2,4-DB. See specific label for surfactant, some combination can increase crop injury.
  Roundup Ready Soybean glyphosate (> 1.125 lb ae/A) POST: Will control or suppress the weed. Repeat application may be necessary.
       

Bigroot morningglory Corn 2,4-D amine (1 pt/A) 2,4-D ester (0.5-0.75 pt/A) POST: Use on actively growing plants that have sufficient vine growth to absorb the herbicide (10"-24"). Suppression giving 50 to 70% control.
  Soybean Cobra (12.5 oz/A) Postemergence. Limited suppression of vines mostly.
  Roundup Ready Corn/Soybean glyphosate (0.75-1.1 lb ae/A) POST: Will control or suppress the weed. Apply when vines are 3" - 6", use higher rate on longer vines. Repeat applications may be necessary. Apply from emergence to V8 (30") RR corn and from emergence through flowering in RR soybean.
       

Canada thistle Corn Stinger (0.3 - 0.67 pt/A) POST: Apply broadcast or spot treatment on Canada thistle shoots that are 4" to bud stage. Do not apply after the corn is 24" tall; do not apply more than 0.67 pt/a per year.
    Hornet WDG (5 floz/A) + Stinger (4 floz/A) PRE or POST: apply when Canada thistle shoots that are 4" to bud stage. The rate provided deliver close to 0.25 lb/a of clopyralid, the active ingredient in Stinger. Do not exceed 0.25 lb/A of clopyralid in one year. Do not to soils that have a pH greater than 7.8 or less than 5.9.
    Banvel/Clarity 0.5-1 pt/a or 2,4-D amine 1 pt/a or ester 0.5-0.75 pt/a POST: Use the 0.5 pt rate of Banvel or Clarity postemergence on sandy soils. On corn between 8"- 36 " use Banvel at 0.5 pt/a. Mostly suppression of shoots.
    Beacon (0.76 oz/a) or Exceed (0.88 oz/a) POST: apply when corn height is between 4" - 20" tall (Beacon) or 4" - 48 (Exceed), and to Canada thistle plants between 2" - 9" tall (Beacon) or 1" - 6" (Exceed). Mostly shoot suppression.
    Laddok S-12 ( 2.33 pt/a) Shoot suppression only. Apply postemergence when Canada thistle is 8" - 10" tall. Use with 2 pt/a COC.
    Buctril 1.5 pt/a or Buctril/atrazine 2 - 3 pt/a POST: Shoot suppression only. Apply to weeds From 8" tall to the bud stage or up to tassel emergence on corn. Do not add spray additives.
  Soybeans Basagran (2 pt/A), Ultra Blazer (1 - 1.5 pt/A), Cobra (12.5 floz/A), Reflex (1.25 pt/A North I-70, 1.5 pt/A South of I-70), FlexStar (1.3 pt/A North I-70, 1.6 pt/A South of I-70) POST: suppression of surface shoots. Apply to from 8" to bud (Basagran), before the 6 leaf stage (Cobra), . Most effective when used in conjunction with narrow rows, i.e., crop shading. See specific label for surfactant, some combination can increase crop injury.
  Roundup Ready Corn glyphsoate (0.75 lb ae/A) Will control or suppress the weed. Apply when Canada thistle is in the bud stage. Do not exceed 1.5 lb ae/A in-crop applications. Application must be made before RR corn is V8 (30" tall).
  Roundup Ready Soybean Corn - glyphosate (0.75 lb ae/A)
Soybean - 1.125 lb ae/A
Will control or suppress the weed. Repeat application may be necessary. Apply when Canada thistle is in the bud stage. Do not exceed 2.25 lb ae/A/in-crop application in RR soybean.

Common milkweed and Hemp dogbane Corn 2,4-D ester (0.5-0.75 pt/A) or 2,4-D amine (1-1.5 pt/A) Apply postemergence. Use drop nozzles when corn is taller than 8".
    2,4-D amine (1 - 2 pt/A) or ester (1 - 2 pt/A) Apply mid- to late-season after corn silks have turned brown and plants are actively growing and have adequate foliage.
    Banvel/Clarity (0.5 to 1 pt/A) See Canada thistle comments
    Beacon (0.38 oz/A)+ 2,4-D or Banvel or Exceed 0.88 oz/a + 2,4-D or Banvel Apply postemergence to corn and to small milkweed/hemp dogbane plants. See label for corn height.
  Corn/Soybeans glyhosate 33% solution (dependent on product) Apply with wiper applicator (rope-wick or sponge) only when there is a sufficient height differential between weed and crop.
    glyphosate 1-2% solution (dependent on product) Spot treat plants that are actively growing. Will kill crop where treated if not glyphosate tolerant.
  STS Soybean Synchrony STS (0.85 oz/A) For shoot suppression of common milkweed. Use only on STS soybean varieties. See label for rate of adjuvant.
  Roundup Ready corn glyphosate (0.75 lb ae/A) Will control or suppress the weed. Repeat application may be required. Applications in bloom stage will provide the most consistent control. Do not exceed 1.5 lb ae/A in-crop applications. Application must be made before RR corn is V8 (30" tall).
  Roundup Ready Soybean glyphosate (1.1-1.5 lb ae/A) Will control or suppress the weed. Repeat application may be required. Applications in bloom stage will provide the most consistent control. Do not exceed 2.25 lb ae/A in-crop applications.

Honeyvine milkweed Corn 2,4-D ester (0.5-0.75 pt/A) or 2,4-D amine (1 pt/A) or Banvel (0.5-1 pt/A) or Banvel + 2,4-D at half rates Apply postermergence. the ester formulation of 2,4-D is preferred; however, a combination of 2,4-D and Banvel may be better than 2,4-D used alone. Check Banvel label for restrictions.
    Beacon (0.76 oz/A) or Beacon + 2,4-D or Banvel (labeled rates) Apply Postermergence. Suppression of shoots only.
    Yukon (6-8 oz/A) May be applied up over the top or with drop nozzles up to 36" corn. Use to suppress plants that are 1 to 6"
    NorthStar (5 oz/A) Apply broadcast to corn 4 to 20" tall, use drop nozzles corn V6 or taller than 20". Use to suppress plants that are 1 to 6".
  Roundup Ready corn glyphosate (0.75 - 1 lb ae/A) Make a second application if necessary. Control may be variable. Do not exceed 1.5 lb ae/A in-crop applications. Application must be made before RR corn is V8 (30" tall). Best results may occur when weed is flowering .
  Roundup Ready soybean glyphosate (1.1-1.5 lb ae/A) Will control or suppress the weed. Repeat application may be required. Do not exceed 2.25 lb ae/A in-crop applications. Best results may occur when weed is flowering .

Jerusalem artichoke Corn Banvel/Clarity (0.5-1 pt/A) or Banvel + 2,4-D at half rates Apply postemergence when weeds are 8" - 16 " tall. Use the 0.5 pt rate of Banvel or Clarity on sandy soils. On corn between 8" - 36" use Banvel at 0.5 pt/a.
    Stinger 0.25 - 0.5 pt/a Apply postemergence to weeds up to the 5-leaf stage. Do not apply more than 0.67 pt/a per year if retreatment is necessary. Do not apply to corn taller than 24".
    Beacon 0.76 oz/a Apply postemergence to 1" -4" tall Jerusalem artichoke plants.
    Spirit (1 oz/A) + dicamba Will provide fair to good control on 6" or less tall Jerusalem artichoke. Apply when corn is 4 to 20" tall, use drop nozzles when corn is above 20" up to 24" tall.
    WideMatch (1.3 pt/A) + dicamba Apply before Jerusalem artichoke is greater than 5 leaves. Apply over the top before corn V5, drop nozzles are required if above V5.
    Hornet (3-5 oz/A) + dicamba Rate is soil dependent. Apply preplant, preemergence, or at the spike stage of corn.
    Northstar (5 oz/A) Apply to 1 to 4" tall Jerusalem artichoke. Apply broadcast to corn 4 to 20" tall, use drop nozzles corn V6 or taller than 20".
  Clearfield corn Lightning (1.28 oz/A) + dicamba  
  Liberty Link corn Liberty (34 floz/A) + atrazine (1 lb ai/A) Will provide suppression.
  Soybeans Pursuit (4 floz or 1.44 oz DF/a) or Classic (0.75 oz/a) Apply Pursuit postemergence to weeds that are 6"- 8" tall and Classic to weeds less than 8" tall. See label for rate of surfactants.
  STS Soybeans Synchrony STS 0.85 oz/a Apply postemergence to weeds that are 2"-6" tall. Use only on STS soybean varieties. See label for rate of adjuvant.
  Roundup Ready corn glyhosate (0.75 lb ae/A) Can suppress. Repeat applications will be needed. Do not exceed 1.5 lb ae/A in-crop applications. Application must be made before RR corn is V8 (30" tall).
  Roundup Ready   soybean glyphosate (1.1-1.5 lb ae/a) Will control or suppress the weed. Repeat application may be necessary. Do not exceed 2.25 lb ae/A in-crop applications.
  Corn/Soybean glyphosate 1 - 1.5% v/v Spot treat plants that are actively growing. Will kill crop where treated.
       

Swamp smartweed Corn Banvel/Clarity (0.5-1 pt/a) Use the 0.5 pt rate of Banvel or Clarity postemergence on sandy soils. On corn between 8" -36" use Banvel at 0.5 pt/a.
Trumpetcreeper Corn/Soybeans glyphosate (1-1.5 lb ae/a or 1.5% v/v) Spot treat in crop (will kill crop where treated). Or apply after harvesting corn, or as a preharvest application in soybeans. Weeds should be actively growing.
  Corn Banvel/Clarity 1 pt/a Apply as a postemergence treatment when corn is between spiking and 8" tall. Mostly suppression of vines.
  Soybeans Cobra, Blazer, Reflex, FlexStar Apply postemergence. Top suppression only. Most effective when used in conjunction with narrow rows, i.e., crop shading.
  Roundup Ready corn/soybean glyphosate (0.75 lb ae/A [corn] 1-1.5 lb ae/A [soybean]) Will control or suppress the weed. Repeat applications will be necessary. See label for sequential treatment rates.
Pokeweed Corn Banvel, Beacon, Exceed or Permit (labeled rates) Apply as a postemergence treatment when weed is small and actively growing. Apply when corn is 8" to 36" tall at least 15 days before tassel.
    Callisto (3 oz/A), Celebrity Plus, Northstar, Yukon, Spirit Apply when plants are less than 12 inches tall.
    Lightning (rate) Apply when plants are less than 12 inches tall in Clearfield corn.
  STS Soybean Synchrony STS (0.5 oz/A)  
  Soybean Classic + Harmony GT  
  Corn/Soybean Glyphosate (1-2% v/v) Spot treat weeds that are less than 24" tall after harvest to new growth.
  Roundup Ready corn/soybean Glyphosate (1.1 lb ae/A) Apply when pokeweed are at least 8" and up to 24" tall.
Dandelion Corn/Soybean 2,4-D ester (1-2 pt/A) Apply before planting. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. If the 2 pt/A rate is used then wait 30 days before planting soybean and 14 days for corn. Control of dandelion with 2,4-D improves as air temperature increases.
  Corn 2,4-D ester 0.75 pt/A Apply as a broadcast postermergence treatment. See label for height restrictions.
Brambles Corn/Soybean 2,4-D ester 0.75 pt/A Apply before planting. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. If the 2 pt/A rate is used then wait 30 days before planting soybean and 14 days for corn.
    glyphosate (0.77-1.1 lb ae/A or 1.5% v/v) Apply as a broadcast or spot treatment prior to planting. Also apply as a spot treatment in crop (will kill crop where treated)
  Corn Banvel/Clarity, 2,4-D (labeled rates) Mostly suppression of top growth. Apply as a broadcast postemergence treatment. Apply when corn is 8" to 36" tall at least 15 days before tassel.
  Roundup Ready Corn/Soybean glyphosate (0.75 lb ae/A [corn] and 1 lb ae/A [soybean]) Apply as a broadcast treatment before soybean are 50% bloom and corn is V8 stage (30").
Curly dock Corn/Soybean glyphosate (0.77-1.1 lb ae/A) + 2,4-D (1-2 pt/A) Apply as a broadcast of spot treatment prior to planting. When using the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. If the 2 pt/A rate is used then wait 30 days before planting soybean and 14 days for corn.
  Corn Banvel/Clarity (0.5-1 pt/A) Apply as a broadcast postemergence treatment. Apply from emergence 36" tall at least 15 days before tassel.
  Roundup Ready Corn/Soybean glyphosate [soybean] (1.1 lb ae/A [corn], 1-1.5 lb ae/A) Will control or suppress the weed. Repeat application may be necessary. See label for sequential treatment rates.
Yellow nutsedge Corn Laddock 5-12 (2.33 pt/A) Apply postemergence, suppression only. Add 2pt/A COC.
    Permit (1.33 oz/A) Apply postemergence to weeds that are 4"-12" inches tall. Add a nonionic surfactant to the spray mix.
    Outlook, Harness, Surpass, TopNotch Soil-applied treatment. Use higher rate for given soil type.
  Corn/Soybean Lasso, Dual II Magnum, Outlook Soil-applied treatment. Use higher rate for given soil type.
    Basagran (2 pt/A) Apply posteremergence 1.5-2 pt/A when plants are 6"-8" tall. Reapply 7-10 days later if needed. Add 2 pt/A COC with each application.
  Soybean Classic (0.5-0.75 oz/A) Apply postemergence. See label for adjuvant rates.
  STS Soybean Synchrony STS 0.85 oz/A Apply postemergence on weeds 3" tall. Use only on STS soybeans varieties. Use 1-2% COC, or 0.25-0.5% NIS. Use the higher rate of adjuvant in dry arid conditions. AMS at 2 lb/A can be added.
Rhizome johnsongrass Corn/Soybean glyphosatre (0.75-1.5 lb ae/A) Apply in the fall prior to when johnsongrass is in the boot to head stage. Apply before ground freezes.
  Corn Accent (1.33 oz/A) as a single or split application Apply postemergence to 8-18" tall johsongrass. Use NIS surfactant at 0.25% v/v or 1% COC.
    Beacon (0.76 oz/A) as a single or split application Apply to johnsongrass when it is 8-16" tall. Add NIS surfactant at 0.25% or COC at 0.25-1% v/v.
  Soybean Assure II (10 oz/A) Apply postermergence to johnsongrass when it is 10"-12" tall. For regrowth retreat with additional 7 oz/A to of 6"-10" of regrowth.
    Fusilade DX (12 oz/A) Apply postermergence to johnsongrass 8-18" talll and retreat 6-12" regrowth at 8 oz/A. Use COC or NIS.
    Fusion (10-12 oz/A) Apply postemergence to johnsongrass from 8-18" tall. Retreat 6-12" regrowth at 8 oz/A. Use COC and NIS.
    Poast Plus (1.5 pt/A) Apply postemergence to johnsongrass 15-25" tall. Use Dash or COC. Retreat at the same rate.
    Select Max (12-32 floz/A) Apply to johnsongrass when it is 4 to 10" tall. Add COC at 1% and AMS at 2 lb/A.
  Roundup Ready Corn/Soybean glyphosate (0.75 lb ae/A - corn and 0.75-1.1 lb ae/A - soybean) Repeat application may be necessary, see label for sequential rates.
    glyphosate (33% v/v) Apply with wiper applicator (rope-wick or sponge) only when there is a sufficient height differential between weed and crop.
Quackgrass Corn Accent (0.67 oz/A) Apply postemergence to 4" - 10" tall quackgrass or apply tip to 1.33 oz/a (in split application) on quackgrass up to 6" tall. Use a nonionic surfactant at 1 qt per 100 gallons of spray or COC at 4 qt per 100 gallons of spray. See label for restrictions.
    Beacon (0.76 oz/A) Apply postemergence to quackgrass when 4" - 8" tall. Control of this species is not immediate and symptoms may take several days to develop. Add nonionic surfactant or COC.
    Exceed 0.88 oz/a + Beacon or Accent (label rates) See label for instructions.
  Corn/Soybeans glyphosate (1 lb ae/A) Apply prior to planting in spring or after harvest in the fall. Weeds should be actively growing and greater than 8" tall.
  Soybeans Assure II (10 oz/A) Apply postemergence when quackgrass is 6" - 10" tall. For regrowth apply 7 oz. when quackgrass is 4 to 8 inches tall. Add COC.
    Fusilade DX (12 oz/A) Apply postemergence to 6" - 10" quackgrass and to 4" - 8" tall regrowth at 8 oz/a. Use COC or nonionic surfactant.
    Fusion (12 oz/A) Apply postemergence to quackgrass 6"- 40" tall. Treat regrowth with 8 oz/a. Use COC or nonionic surfactant.
    Poast Plus (2.25 pt/A) Apply postemergence to quackgrass 6"- 8" tall and retreat at 1.5 pt/a for regrowth. Use Dash or COC at 2 pt/a.
    Select Max (12-32 floz/A) Apply postemergence to quackgrass 4" - 8" tall and on regrowth as well. Add COC.
  Roundup Ready corn/soybean glyphosate (0.75-1.1 lb ae/A) Will control or suppress the weed. Repeat application may be necessary. See label for sequential treatment rates.
Wirestem muhly Soybeans Assure II (8 oz/A) Apply postemergence when wirestem muhly is 4" - 8" tall. For regrowth, apply 7 oz/a. Add COC.
    Fusilade DX (12 oz/A) Apply postemergence to 4" - 12" wirestem muhly and apply to regrowth at same size and rate. Use COC or nonionic surfactant.
    Fusion (8 oz/A) See Fusilade DX comments.
    Poast Plus (2.25 pt/A) Apply postemergence to wirestem muhly up to 6" tall and retreat at same rate for regrowth. Use Dash or COC.
    Select Max (1 pt/A) Apply postemergence to 4" - 8" wirestem muhly and retreat at same rate for regrowth. Add COC.
  Corn Accent (0.67 oz/A) See quackgrass comments.
    Beacon (0.76 oz/A) Apply postemergence. Suppression only.
  Corn/Soybeans glyphosate (0.75-1 lb ae/A) See quackgrass comments.
  Roundup Ready corn/soybean glyphosate (0.75 lb ae/A) Repeat application may be necessary. See label for sequential treatment rates.
     
Small Grain Cover Crop    
Rye or Wheat Corn/Soybeans glyphosate (0.75 lb ae/A) Apply prior to planting. Add a nonionic surfactant at 0.5% v/v and apply in 10 gallons of water per acre.
    Gramoxone Extra (1.5 - 3 pt/A) Apply prior to planting. Add a nonionic surfactant or COC and depending on the size of the apply in a minimum of 20 gallons of water per acre.
  Corn Atrazine + Gramoxone Extra (label rates) Apply as a burndown treatment prior to planting. Add a NIS or COC.
       
Grass/legume Sods    
Orchardgrass or Fescue Sod Corn/Soybean glyphosate 0.77 lb ae/A in fall; 1.5 lb ae/A in spring Grass sod is easier to control with glyphosate when applied in the fall before a killing frost. Higher rates of glyphosate are required to kill grass sod in the spring before planting.
  Corn Atrazine + Gramoxone Extra (label rates) Apply as a burndown treatment before planting. Add a COC. May require a postemergence application of atrazine if label allows.
  Soybean Sencor/Lexone + Gramoxone Extra (label rates) Apply as a burndown treatment before planting. Add a COC. May require a postemergence treatment of Poast Plus for control or suppression of regrowth.
Alfalfa sod Corn/Soybeans glyphosate (0.77-1 lb ae/A) Apply as a burndown treatment to actively growing alfalfa in the fall before a killing frost. For spring applications: apply 2.5 - 3 qt/a to alfalfa sod with sufficient growth.
  Corn

Banvel (0.5 pt/a) and/or
2,4-D (1 - 2 pt/a), or Banvel + atrazine

Apply as a burndown in the spring before planting. Sufficient growth of the alfalfa is required for good control.
  Soybeans 2,4-D ester 2 pt/A Apply as a burndown at least 30 days before planting. Control alfalfa before planting soybeans.
Clover sod Corn/Soybean glyphosate (0.5 - 1 lb ae/A) + 2,4-D ester (1 pt/A) Apply as a burndown before planting. For the 2,4-D at 1 pt, wait 7 days before planting corn or soybean. If the 2 pt/A rate is used then wait 30 days before planting soybean and 14 days for corn.
  Corn Atrazine Apply as a burndown treatment before planting. Add COC. May require a follow-up, postemergence treatment of 2,4-D or Banvel/Clarity
    Banvel (0.5 pt/A) and/or
2,4-D (1 to 2 pt/A) or Banvel + atrazine (label rate)
Apply as a burndown in the spring before planting.
  Soybean 2,4-D ester 2 pt/A Apply as a burndown at least 30 days before planting soybean. Control clover before planting.
       


* Burndown - application of herbicide on postemergent weeds but before planting the crop. FALL - applications made after harvest but before the ground freezes. PRE - herbicides applied before the crop and weeds emerge. POST - herbicide applied after the crop and weeds have emerged.
   
References:
1. Mark M. Loux, Jeff M. Stachler, William G. Johnson, Glenn R.W. Nice, and Thomas T. Bauman. 2007 Weed Control Guide for Ohio and Indiana. The Ohio State University Extension and Purdue University Extension. WS-16.
2. Scott A. Nolte, Bryan G. Young and Gordan R. Roskamp. 2002. Common pokeweed control in corn and soybean. North Central Weed Science Society Abstracts. 57:122.
3. Loux, M., J. Stachler, B. Johnson, G. Nice, V. Davis, and D. Nordby. 2006. Biology and Management of Horseweed. [http://www.ces.purdue.edu/extmedia/GWC/GWC-9-W.pdf]
4. Dan Childs, Thomas Jordan, and Meril Ross. Weed Control in No-till Systems. Purdue University.
REV 12/2007
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture Cooperating. H.A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the Acts of May 8 and June 30, 1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to our programs and facilities.