Fall Control of Chickweed and Horseweed

November 30, 2011 in Uncategorized

Chickweed is a common weed of small grains in Delaware.  Control is usually accomplished with a herbicide application in the spring, thought fall applications are becoming more common.  Marestail is another weed we see growing in small grains, but mostly a problem in full season soybeans.  Below is more information of these two weeds:

With the recent stretch of nice fall weather, we continue to get questions about control of certain winter annual weeds, namely common chickweed and horseweed/marestail.
Horseweed has been a growing concern the past several years and although we have conducted research on this weed, Mark Loux and his colleagues at Ohio State have some helpful insight on this specific species. Instead of reinventing the wheel, here are a few highlights and references to his articles for further information.

  • Keep cost of fall herbicide treatments in the range of $4–12/acre. Glyphosate + 2,4–D can be an initial low cost option to consider that provides control of a relatively broad spectrum of weeds.
  • Products that contain chlorimuron (e.g., Canopy) tend to provide the most residual horseweed control into spring. (Keep in mind there are areas in Delaware, Maryland and in the Midwest that have ALS+glyphosate—resistant horseweed, so chlorimuron or other ALS herbicides would not provide control in these situations.)
  • Fall only burndown/residual applications generally do not provide enough control of horseweed into next season. Two-pass burndown programs (fall followed by spring applications) are better at obtaining season-long horseweed control.
  • If applying a fall burndown, make sure to select the correct product depending on what crop you intent to plant next spring. For example, don’t apply a Canopy product if you plan to plant corn.

horseweed

(Photos of horseweed taken in early November. Curran, Penn State)

For more details on the above points, please review articles about horseweed management from Ohio State:
Fall Herbicide Treatments – Focus on Marestail Management
http://corn.osu.edu/newsletters/2010/2010-30/fall-herbicide-treatments-2013-focus-on-marestail-management/?searchterm=marestail
Do We Need a Systems Approach to Marestail Management?
http://corn.osu.edu/newsletters/2011/2011-03/do-we-need-a-systems-approach-to-marestail-management/?searchterm=marestail
What We Learned About Marestail in 2010
http://corn.osu.edu/newsletters/2011/2011-03/what-we-learned-about-marestail-in-2010/?searchterm=marestail
Common chickweed in another weed we have been hearing more about not only in small grains but in forage crops as well. In wheat, barley, and oats, unless it is ALS-resistant, Harmony Extra (or equivalent generic product) is one of the better options. (On as side note, if you have horseweed in small grains, Harmony Extra usually provides good control.) If you are one of the unfortunate who have an ALS-resistant chickweed population then programs that include Starane (fluroxypyr) appear to be providing the best control. We are currently conducting a couple studies on ALS-resistant chickweed in small grains, so we hope to have a better handle on this by next spring.
If chickweed is a problem in alfalfa, then some options include Pursuit, metribuzin, Chateau, and Gramoxone. Only Pursuit and metribuzin are labeled for use in alfalfa/grass mixtures. Also, as we get later in the year, products like Pursuit tend not to be as effective due to colder conditions that affect weed growth. If you are struggling with chickweed in grass hay or pasture, a combination of dicamba (Clarity, Banvel, others) plus 2,4–D will provide some suppression (70–80% control). This tank-mixture works better on chickweed in the fall compared to spring applications where it typically provides only about 50–60% control.
 
Source:

Lingenfelter, Dwight.  2011. Tidbits on Fall Control of Chickweed and Horseweed.  Field Crop News, Vol. 11:31, November 8, 2011.  Penn State Extension.  Online. http://extension.psu.edu/field-crop-news/archives/2011/november-8#f

Marestail Control for Next Year’s Soybeans

October 7, 2009 in Uncategorized

The following is a good article on marestail control for next year’s soybean crop. Fall treatments can have a role but cannot take the place of preplant treatments in the Spring.

Post-emergence control of many marestail populations in the soybean growing season is close to impossible due to herbicide resistance. The goal of a marestail management program is to ensure that the combination of fall and spring burndown and residual herbicides results in a weed-free seedbed at the time of soybean emergence, and little to no emergence of marestail between soybean emergence and crop canopy closure. Even the most effective marestail management programs can fail to completely achieve this, but they often keep the populations low enough in the soybeans that they are not problematic.

Marestail plants that emerge in late summer or fall are easily controlled with a fall herbicide treatment. However, it’s essential to realize that a fall herbicide treatment is not likely to accomplish everything that’s needed in an effective marestail management program. An effective program does not necessarily involve application of herbicide in the fall. A combination of the appropriate burndown and residual herbicides applied in April can adequately control marestail, even those that emerged the previous fall. So, one option in fields where other winter weeds are not a problem is to skip the fall herbicide treatment and apply a combination of burndown and residual herbicides in April when marestail are still small.

In those marestail-infested fields requiring a fall herbicide treatment for management of other winter annual annual weeds or dandelion, it is essential not to apply all of the residual herbicide in the fall. This also applies to those fields that are typically so wet that soybeans cannot be planted until mid to late May. In this situation, the goal of a fall residual herbicide treatment might be just to ensure that marestail are not too large when burndown herbicides are finally applied in May. Regardless of the type of herbicides applied in fall, an effective rate of a residual herbicide should still be applied in the spring, to maximize control of marestail that emerges in May and June. The most effective residual herbicides for spring application include two modes of action, to ensure effectiveness on ALS-resistant marestail. Examples: Envive, Valor XLT, Gangster, Sonic, Authority First, and Canopy DF + metribuzin. However, it should not be necessary to apply something this broad-spectrum or costly in the fall. We suggest one of the following approaches:

1. Apply a combination of glyphosate and 2,4-D in the fall, followed by application of residual herbicide in the spring prior to soybean emergence. At the time of soybean planting, the field is likely to be infested with marestail that emerged earlier in spring, so include effective burndown herbicides (2,4-D, Gramoxone, glyphosate, or Ignite or some combination as appropriate based on herbicide resistance, plant size and time until soybean planting) to control emerged plants.

2. Apply 2,4-D with Canopy DF or EX at fairly low rates (e.g. 1 oz of EX or 2 oz of DF) in the fall, followed by application of residual herbicide in the spring (with burndown herbicides if the residual from fall does not hold marestail through planting). It is possible to follow the fall Canopy application with a spring application of a chlorimuron-containing herbicide, as long as the total does not exceed the maximum labeled rate of chlorimuron for the soil type.

3. In ALS-resistant populations where Canopy will fail to provide any residual control of marestail, it may be possible to substitute a combination of 2,4-D with metribuzin in the fall. This combination should control most emerged winter annuals, but can be weak on dandelion. Follow with application of residual herbicide in the spring (with burndown herbicides if the residual from fall does not hold marestail through planting).

The idea here is to apply an herbicide treatment in the fall that adequately controls emerged weeds, provides some residual if desired, but does not break the bank and allows use of the majority of the residual herbicide in the spring. Options 2 and 3 would be most suitable for fields that are wet well into spring, where the goal is to control at least some of the marestail that emerge in early spring. Canopy certainly provides substantially longer residual than metribuzin, but use of metribuzin preserves the option to plant corn the following spring.

Adapted from “Fall and Spring Herbicide Treatments for Management of Marestail – How to Use the Residual Herbicide?” by Mark Loux in the current issue of the Crop Observation and Recommendation Network Newsletter from the Ohio State University http://corn.osu.edu/index.php?setissueID=325

Large Marestail Control in Fields to go into Soybeans

June 18, 2009 in Uncategorized

There are many fields to go into soybeans that have not been able to be planted and marestail is getting very large. Control of large marestail can be difficult, especially with glyphosate resistant types. The following are some recommendations.

Many soybean fields have not yet been planted due to the wet weather and marestail is getting very tall. Ideally, we would target marestail when it is small with 2,4-D or dicamba or paraquat ahead of planting. With large marestail, 2,4-D and paraquat are not effective and higher rates of dicamba that would be effective will result in a long waiting period to plant soybeans due to soil activity and possible damage to the beans. This means that you will need to consider other options.

For large marestail in fields to go into soybeans one option is Ignite (glufosinate). Remember that Ignite is weak on grasses so it will need to be mixed with another material. A second option is using a high rate of Classic (chlorimuron) or Synchrony on STS beans.

Growers should note that we are starting to see marestail resistant to the ALS herbicides (Classic or Synchrony are in that category) in addition to glyphosate resistant marestail. If you have marestail resistant to both then Ignite is the best option.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County.

Controlling Marestail Escapes in Soybeans

June 3, 2009 in Uncategorized

The followng is a short article on controlling marestail escapes in soybeans.

Is it possible to control marestail in emerged soybeans? In numerous no-till soybean fields, omission of 2,4-D ester in burndown treatments resulted in a failure to control marestail, and soybeans have now emerged. As many growers know from previous experience, it can be almost impossible to adequately control marestail plants that have recovered from earlier treatments with herbicide. The best case here is that the marestail plants are not herbicide-resistant, and the soybeans are Roundup Ready, which allows use of a high rate of glyphosate or a combination of glyphosate plus FirstRate or Classic. Resistance to glyphosate and/or ALS inhibitors will limit the effectiveness of these treatments. Control is more difficult in non-GMO soybeans, since FirstRate and Classic are the only options. These two herbicides are not that good on large marestail anyway. All (yes – all) other postemergence soybean herbicides have essentially no activity on marestail, and usually cannot be counted on to even slow the growth of marestail.

Information from Mark Loux, the Ohio State University.

Don’t Forget About Glyphosate Resistant Marestail

April 30, 2009 in Uncategorized

Glyphosate (Roundup) resistant marestail can be found throughout Delaware. Don’t forget to use use another herbicide prior to planting soybeans to control these resistant marestail plants. The following is a short article on the subject.

The majority of marestail usually emerges in the fall, it can also emerge in spring and early summer. Marestail is more easily controlled when small in late fall or early spring. As it matures and bolts in the spring and early summer, herbicides become less effective at killing this weed. In addition to glyphosate resistance, it looks like our first cases of marestail resistant to the ALS inhibitors (Classic FirstRate, etc.) are being found on Delmarva (they are being tested at this time). At this point in time (late April or early May), the most economical treatments for control include 2,4-D ester at 1 to 2 pints/acre in combination with glyphosate or Gramoxone. Even 2,4-D ester should be applied to small plants (less than 2 inch rosettes) to ensure effective control. Dicamba (Banvel or Clarity at 6 to 8 oz/acre) can also be used but must be applied at least 30 days in front of soybean planting. A primary goal for horseweed management in soybean (or corn) should be effective control of emerged plants prior to planting.

Information from a number of sources including Penn State and UD.

Control Marestail Before Planting Soybeans

March 20, 2009 in Uncategorized

We have glyphosate resistant marestail across the state. For soybeans, you need to take steps to control marestail before planting and assume that you have herbicide resistant marestail. The following are some recommendations.

Existing horseweed plants should be controlled before they exceed 6 inches in height. While glyphosate remains effective on many other weed species, tank-mix partners or alternative herbicides are needed to provide adequate burndown control of glyphosate-resistant horseweed. Dicamba, paraquat, and 2,4-D are other herbicides that can be used to control horseweed prior to corn or soybean planting. Research has repeatedly demonstrated improved control of emerged horseweed from applying two- or three-way herbicide tank mixtures as compared with single-herbicide burndown treatments.

Both amine and ester formulations of 2,4-D are labeled for burndown applications prior to soybean planting, but the ester formulation is usually preferred over the amine formulation. The low water solubility of an ester reduces the potential for it to be moved into the soil by precipitation, where it could cause severe injury to germinating soybean seed. Also, the ability of esters to better penetrate the waxy leaf surfaces of weeds often results in improved control of large weeds and during periods of cool air temperatures. The labels of many 2,4-D ester formulations (3.8 lb acid equivalent per gallon) allow applications of up to 1 pint per acre 7 days prior to soybean planting; increasing the rate to more than 1 pint increases the waiting interval to 30 days.

Distinct and Clarity are dicamba-containing products labeled for preplant applications in corn (Clarity only) or soybean (both products). Corn is much more tolerant of dicamba than soybean, so additional use precautions must be followed when using dicamba prior to soybean planting. For example, both labels indicate that a waiting interval and precipitation event must occur between dicamba application and soybean planting. An application of Clarity, at 4 to 16 fluid ounces per acre, must be followed by at least 1 inch precipitation and a waiting interval of 14 days (for applications of up to 8 fluid ounces) or 28 days (for applications between 8 and 16 fluid ounces) before planting soybean. The Distinct label allows 2 to 4 ounces per acre to be applied, followed by a minimum of 1 inch precipitation and a waiting interval of 30 days before soybean planting. If you plan to use dicamba as part of your burndown herbicide program in 2009, keep these intervals and precipitation requirements in mind so as to make timely applications that preclude planting delays.

Information adapted from an article in the March 9, 2009 edition of the University of Illinois Bulletin for IPM.

Controlling Weed Escapes in Roundup Ready Beans

July 17, 2008 in Uncategorized

The following is a good article on controlling weed escapes in Roundup Ready soybeans from the Ohio State University.

This is the time of year when we get phone calls about rescuing weed control in Roundup Ready soybean fields, and we hear most often about marestail, giant ragweed, and lambsquarters. Less than adequate weed control after several herbicide applications can often be attributed to failure to use the appropriate combination of herbicides and application timings for the weed population. However, adverse weather, crop replants, and slow crop development can also negatively impact weed control programs. Weeds that survive into mid-season can also be indicative of herbicide resistance, or a developing herbicide resistance problem. Before spending additional money on a late-season POST herbicide application, it’s important to consider what the goal of the application is, and whether any effective herbicide options remain based on what has already been applied this season.

For example, a marestail plant that has survived previous application of glyphosate plus an ALS inhibitor (FirstRate or chlorimuron) is not likely to be controlled by additional herbicide applications. A late-season application that does not control marestail will also fail to suppress it enough to make harvest any easier. On the other hand, small soybeans that are infested with late-emerging marestail plants, which have not been subject to a prior herbicide treatment, may merit an additional application where the marestail is known to be still sensitive to glyphosate or ALS inhibitors. Where someone is determined to treat marestail that have survived previous application, our recommendation is typically going to be something like a full rate of FirstRate or Classic plus up to 1.5 lbs ae/A of glyphosate. The cost of this, up to $25 or more based on current glyphosate prices, has to be weighed against its possible effectiveness.

For both lambsquarters and ragweeds, it is possible that a second POST application of glyphosate will control plants that survived a previous application. However, as we have stated in previous C.O.R.N. articles, this is most likely to occur where the first application greatly suppressed the weeds (70 to 80% control at least), and the second glyphosate treatment is applied about 3 weeks of the first. Where the previous glyphosate application had little effect on the weeds, an alternative to glyphosate would be required in the second application for control of ragweeds. There are essentially no consistently effective alternatives to glyphosate for control of large lambsquarters.

Choices for ragweeds include FirstRate, Classic, Cobra/Phoenix and Flexstar, and the decision here should be based on several factors. Classic or FirstRate would generally be the most effective option where the population is known to be still sensitive to ALS inhibitors. Where ALS resistance is known or suspected, we would suggest use of Cobra or Phoenix. Use of Flexstar should generally be curtailed as we move later into the season, since it has more restrictive guidelines for crop rotation. Where the glyphosate had substantial activity on the weeds in the first application, the second application should generally contain glyphosate plus one of the alternatives mentioned here. Keep in mind the following also: 1) expectations should be lowered for late-season applications to large weeds – plant death may not occur, but harvest problems may at least be reduced; 2) maximum labeled rates of the alternative to glyphosate are likely to be needed; 3) spray adjuvants should be optimized for the alternative; and 4) spray coverage should be maximized through use of slower application speeds, higher volumes, and nozzles that provide a greater number of relatively small droplets (for example, extended range flat fans instead of ai nozzles). As stated previously, the possible merits of a late-season application to large weeds have to be weighed against the cost and risk of soybean injury.

Reprinted in part from “Late-Season POST Herbicide Applications in Soybeans” by Mark Loux in the July 14, 2008 edition of the Crop Observation and Recommendation Network newsletter from the Ohio State University.

Management of Glyphosate-Resistant Horseweed (Also Called Marestail) in No-Till Soybeans

January 4, 2008 in Uncategorized

We had too many soybean fields in Kent County that had marestail escapes in 2007. With much of the marestail being glyphosate (Roundup) resistant, other control strategies are needed in no-till. The following is an article on the subject.

Local extension specialists do not recommend the use of glyphosate (Roundup, Touchdown, and others) for preplant weed control with Roundup Ready soybeans. Glyphosate will be used at least once after the soybeans are planted, and it is always good management to vary the mode of action of herbicides used for controlling weeds. Glyphosate-resistant horseweed has been identified throughout the mid-Atlantic region in a very short period of time. Horseweed seed are very small and have a tuft of hairs (called pappus) that allows them to be blown by wind for long distances. Its rapid spread has resulted in the need to treat all horseweed as glyphosate-resistant plants.

Dicamba (Banvel, Sterling, Clarity) or 2,4-D based programs provide the best opportunity for successful horseweed control in no-till soybean. Dicamba at 6 to 8 oz/A or 2,4-D at 32 oz/A plus Gramoxone Inteon at 2 pt/A must be applied at least 30 days before soybean planting. These applications can be made while horseweed plants are small and easier to control. 2,4-D at 16 oz/A plus Gramoxone Inteon at 3 pt/A can be applied from seven to 30 days before planting, but the 2,4-D rate is lower and horseweed is bigger, so control will not be as good as the 30 day before planting program. Do not rely solely on paraquat for horseweed control on a yearly basis.

A number of weed species have developed resistance in Ohio over a short period of time to the type of herbicide chemistry in FirstRate and Classic. Horseweed plants in Ohio have developed resistance to these herbicides, and it is likely that it could happen in the mid-Atlantic region as well. For this reason, the use of FirstRate (contains the active ingredient cloransulam) for preplant horseweed control is not recommended by extension specialists in the mid-Atlantic region. FirstRate should be reserved for postemergence use, when needed, to provide suppression of escaped horseweed plants. Canopy or Synchrony XP (which contain chlorimuron, the active ingredient in Classic) should only be used prior to planting soybeans when burndown applications have been delayed too long to use dicamba or 2,4-D based programs, and should not be used in consecutive years.

Spring tillage is an alternative and is a very effective option for controlling horseweed.

Risk for selecting glyphosate-resistant horseweed is greater when soybeans are planted on a frequent basis. Planting soybeans one out of two years appears to lessen the risk of developing glyphosate resistance, but does not eliminate the risk. If soybeans are planted more frequently than three out of six years, periodic use of tillage is recommended. Tillage in two out of six years is encouraged to minimize the impact of developing glyphosate-resistant biotypes.

Other weed species in the mid-Atlantic region can develop resistance to glyphosate. Also, it is likely that a shift in the weed population may develop when glyphosate does not adequately control some of the weed species present. As a result, it is recommended that you use a variety of tactics for weed control. Frequent use of Roundup Ready soybeans (more frequently than three out of six years) is discouraged. Rather, use of non-glyphosate based weed control programs (a soil-applied preemergence herbicide program followed by an appropriate postemergence herbicide when needed) should be used periodically in combination with tillage and crop rotation when and where possible. It is not advisable to use Roundup Ready crops repeatedly in the same fields on an annual basis. As a general rule, do not use Roundup Ready crops in the same field two years in a row.

From the factsheet “Management Of Glyphosate-Resistant Horseweed (Also Called Marestail) In No-Tillage Soybeans” Prepared by Mark VanGessel, University of Delaware; Bradley Majek, Rutgers University; Ronald Ritter, University of Maryland

Control Marestail

September 22, 2007 in Uncategorized

Marestail was a very bad problem in soybean fields in Kent County this year. The following is an article on how to control marestail starting this fall.

We are continuing to see an explosion of horseweed or marestail in many areas of the state this summer. Horseweed in present in agricultural fields throughout the state, and is a frequent species along roadsides and in noncropland. This time of year, the seeds are moving with the wind in hopes of landing in an opportune location where they can germinate and begin the next generation. We don’t know how much of this horseweed is herbicide resistant, but rest assured that the resistance problem continues to grow and spread.

As everyone knows, the biggest problem has occurred in no—till Roundup Ready soybeans where glyphosate is used exclusively as the weed control tool. Even with two well—timed glyphosate applications, resistant horseweed may/will not be effectively controlled. Horseweed can emerge in the fall as well as in spring and early summer. Emerged horseweed is more easily controlled when small in late fall or early spring. As it matures and bolts in the spring and early summer, herbicides become less effective at killing this weed (this is true even for glyphosate susceptible biotypes and also for 2,4–D). In addition to glyphosate resistance, populations in Ohio and Indiana are also resistant to the ALS inhibitors (Classic FirstRate, etc.). We are also hearing reports of FirstRate failure in Pennsylvania. At this point, the most economical treatments for control includes 2,4–D ester at 1 to 2 pints/acre probably in combination with glyphosate or possibly Gramoxone. A primary goal for horseweed management in soybean should be effective control of emerged plants prior to planting.

Here are some important principles for horseweed control:

2,4–D ester should be included in herbicide treatments if at all possible. In the spring time, apply at least 30 days before planting at 1 qt/A.

Herbicides applied in the fall will control emerged horseweed, but may not adequately control spring emerging plants. Residual herbicides such as Canopy, Valor, or Sencor applied in the fall can control horseweed through soybean planting. In trials, Canopy products (Canopy, Canopy EX, Canopy XL, etc.) have been the most consistent fall applied products for general winter annual weed control before soybeans. Include 2,4–D with the fall application and glyphosate if grassy weeds are present.

Spring herbicides should be applied when horseweed plants are no more than 4 to 6 inches tall. Horseweed seedlings or rosettes (April) are easiest to kill.

Spring applications prior to May should include a residual herbicide to control later–emerging plants.

Mark VanGessel at Delaware has demonstrated some promising results with fall seeded cover crops such as cereal rye. The Delaware research suggests that horseweed is not very competitive when other plants such as cereal rye are growing in the field. A fall seeded cover crop may not only provide winter cover, hold nutrients, and other important benefits, but could also help reduce horseweed establishment and success.

From the September 19 issue of Penn State Field Crop News “Consider Horseweed/Marestail Management Now” by Bill Curran, PSU Weed Specialist

Control Marestail

September 10, 2007 in Uncategorized

There are too many marestail escapes in soybeans this season. Any fields that are to go into soybeans next year should be targeted to control this problem weed. The following is an article on the subject.

We are seeing an explosion of horseweed or marestail in Delaware. This time of year, the seeds are moving with the wind in hopes of landing at an opportune location where they can germinate and begin the next generation. Horseweed was a common site throughout Delaware in soybean fields this summer, but also along roadsides and other non-crop areas. Some of this marestail is likely glyphosate resistant.

The biggest problem of resistance has occurred in no-till Roundup Ready soybeans where glyphosate is used exclusively as the weed control tool. Even with two well-timed glyphosate applications, resistant horseweed may/will not be effectively controlled. While the majority of horseweed usually emerges in the fall, it can also emerge in spring and early summer. Horseweed is more easily controlled when small in late fall or early spring. As it matures and bolts in the spring and early summer, herbicides become less effective at killing this weed. In addition to glyphosate resistance, populations in the country are also becoming resistant to the ALS inhibitors (Classic FirstRate, etc.) and we should expect this also in Delaware. At this point in time, the recommended treatments for control include 2, 4-D ester at 1 to 2 pints/acre, in combination with Gramoxone. Even 2, 4-D ester should be applied to small plants (less than 2 inch rosettes) to ensure effective control. In Delaware, dicamba (Banvel or Clarity at 6 to 8 oz/acre) can also be used at least 30 days in front of soybean planting (see recommendations below). A primary goal for horseweed management in soybeans should be effective control of emerged plants prior to planting. Here are some important principles for horseweed control:

>2,4-D ester should be included in herbicide treatments if at all possible.

>Herbicides should be applied when horseweed plants are no more than 4 to 6 inches tall. Horseweed seedlings or rosettes (April) are easiest to kill.

>Herbicides applied in the fall will control emerged horseweed, but may not adequately control spring emerging plants. Residual herbicides, Canopy, Valor, or Sencor, applied in the fall can control horseweed through soybean planting.

>Spring applications, prior to May, should include a residual herbicide to control later-emerging plants.

University of Delaware, Maryland, and Rutgers recommendations focus on not using glyphosate in the burndown and recommend Gramoxone combinations. Timing is important. The early pre-plant programs may require an additional application of Gramoxone at planting due to later emerging weeds or horseweed that was not completely controlled. The less than 7 day programs should not be used in consecutive years because of concerns for resistance and split applications are preferred over the single more risky application.

Spring application more than 30 days before planting — Apply Gramoxone Inteon at 2 pt/acre plus dicamba (Banvel or Clarity at 6 to 8 oz/acre) or 2, 4-D ester at 1 qt/acre + NIS (the Clarity label requires a minimum of 1″ of rainfall followed by 14 days before soybean planting).

Less than 30 days, but more than 7 days before planting – Apply Gramoxone Inteon at 3 pt/acre + 1 pt 2,4-D ester + NIS.

Less than 7 days before planting — A.) Apply Gramoxone Inteon at 3.8 pt/acre + NIS, 3 to 5 days before planting followed by Gramoxone Inteon at 2 pt/acre + NIS at planting or B.) Apply Gramoxone Inteon at 3.8 pt/acre + Canopy or Synchrony XP at 1.5 to 2.5 oz/acre + NIS.

Mark VanGessel at the University of Delaware has demonstrated some promising results with fall seeded cover crops such as cereal rye. The Delaware research suggests that horseweed is not very competitive when other plants such as cereal rye are growing in the field. A fall seeded cover crop may not only hold nutrients and provide winter cover and other important benefits, but could also help reduce horseweed establishment and success.

Extracted and modified from the Penn State Field Crop News, September 19, 2006 issue