MSU Extension

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.  

The 2008 Weed Control Guide for Field Crops, Extension Bulletin E-434 is now available online at http://www.msuweeds.com/publications/2008_weed_guide/. It is also available in print at the MSU Extension Bulletin office by calling (517)353-6740 or your county Extension office.

The 2008 Weed Control Guide provides the latest up-to-date information on weed management recommendations in corn, soybeans, small grains, forages, dry edible beans, potatoes, sugar beets and sorghum. Other features include: an up-to-date table on the current glyphosate products that are labeled for use in Michigan, information on rain-free periods of different herbicides, instructions on how to submit a sample to the diagnostic clinic, and a complete table on crop rotation restrictions. Additionally, a new glossary of restricted use pesticides (RUP), groundwater advisories, signal words, and restricted entry intervals (p. 152-155) is included in this year’s guide. This information will be extremely helpful in the record keeping process of commonly used herbicides. Seven fact sheets on the control of hard-to-control weeds are included in the guide (p. 161-169). The fact sheets contain the most current recommendations for control of dandelion, controlling grasses in winter wheat, white campion (white cockle), horseweed (marestail), wild carrot, Canada thistle, common pokeweed and hemp dogbane. Information on the new herbicides for the 2008 Weed Control Guide is updated below.

Corn (p. 18-47)

This year there has been some significant changes to the rotation restrictions for products that contain the active ingredient acetochlor. The rotational options for straight acetochlor products Harness, Surpass, Breakfree, Volley, Degree and Topnotch have been expanded to four months for wheat and to next spring (nine months) for soybean, oats, barley, rye, dry beans, sugar beets and potatoes. For the acetochlor products that also contain atrazine, Harness Extra, Keystone, Keystone LA, FulTime, Breakfree ATZ, Breakfree ATZ Lite, Degree Extra and Fultime, the rotation restrictions are nine months for soybean and 15 months for alfalfa, dry beans, wheat, oats and potatoes. Although the rotation restriction has also been shortened for sugar beets, we are still recommending 21 months before rotating to sugar beets.

There were several new herbicides added to the corn section. These products include Breakfree (p. 19), Breakfree ATZ (p. 41), Breakfree ATZ Lite (p. 41), Halex GT (p. 36, 41), Rage D-Tech (p. 40, 42), SureStart (p. 42) and Status (p. 25).

Breakfree 6.4EC (acetochlor + safener) is a new herbicide marketed by DuPont and is similar to the acetochlor product Surpass. Breakfree controls several annual grass species and some small seeded broadleaf weeds, like pigweed. The typical use rate recommended for Michigan is 2 pt/A, however this rate can vary depending on soil type and organic matter.

Breakfree ATZ 5.25L andBreakfree ATZ Lite 5.5L are two new premixes marketed by DuPont that contain Breakfree (acetochlor + safener) and atrazine. These products are similar to Keystone and Keystone LA. The major difference between Breakfree ATZ and Breakfree ATZ Lite is the amount of atrazine in these premixtures. For example, the typical use rate for Breakfree ATZ is 2.2 qt/A. At this rate, BreakFree ATZ would contain 2 pt/A of Breakfree and 1.2 qt/A of Atrazine 4L. The typical rate for Breakfree ATZ Lite is 2 qt/A, which would contain 2 pt/A of Breakfree and 0.75 qt/A of Atrazine 4L.

Halex GT 4.38L (mesotrione + glyphosate + s-metolachlor) is a new premixture marketed by Syngenta for early postemergence application in glyphosate-resistant corn only. Halex GT combines the residual activity of Dual Magnum and Callisto with Touchdown HiTech for control of broadleaf and grass weeds in glyphosate-resistant corn including common and giant ragweed, waterhemp, lambsquarters, pigweeds and foxtails. The typical use rate of Halex GT ranges from 3.6 to 4.0 pt/A that can be applied from emergence up to 30 inches tall corn or the 8-leaf stage, whichever is the most restrictive. The 3.6 pt/A rate of Halex GT contains 1 pt/A of Dual Magnum, 3 fl oz/A of Callisto and 24 fl oz/A of Touchdown HiTech. Halex GT must be applied with a non-ionic surfactant (NIS) at 0.25 percent v/v and ammonium sulfate at 17 lb/100 gal is recommended. The addition of 0.25 to 0.5 lb/A atrazine may provide additional control of hard-to-control weeds and in areas with heavy weed pressure. Be aware that there are restrictions for using organophosphate (OP) insecticides with Halex GT.

Rage D-Tech 4.06EW (carfentrazone-ethyl + 2,4-D ester) is a new premixture marketed by FMC. This combination of Aim and 2,4-D ester can be used for burndown prior to corn planting or postemergence applications from spike to 8-inch tall corn. For burndown uses, Rage D-Tech can be applied at 0.75 pt/A with a crop oil concentrate (COC) at one percent v/v. At this rate, Rage D-Tech will contain 0.82 fl oz/A of Aim and 0.78 pt/A for 2,4-D ester. For postemergence use, do not apply more than 8 fl oz/A of Rage D-Tech plus a non-ionic surfactant (NIS) of 0.25 percent v/v.

SureStart 4.16EW (acetochlor + flumetsulam + clopyralid) is a new premix of Surpass + Python + Stinger marketed by Dow AgroSciences for preplant, preemergence, or early postemergence applications up to 11-inch tall corn prior to applying glyphosate in glyphosate-resistant corn or Liberty application in Liberty Link corn. The typical use rate of SureStart ranges from 1.5 to 2.0 pt/A depending on soil texture and organic matter content. SureStart at 1.75 pt/A contains 1.03 pt/A of Surpass, 2.7 fl oz/A of Stinger, and 0.52 oz/A of Python. SureStart will provide initial control of annual grasses, pigweeds, common ragweed, and common lambsquarters. Be aware that there are restrictions for use with OP insecticides and if the soil pH is greater than 7.8 or organic matter is less than 1.5 percent.

Status 56WG (dicamba + diflufenzopyr + safener) is a new postemergence herbicide being marketed by BASF. Status contains the herbicide Distinct plus a new safener which allows for postemergence applications from four to 36-inch tall corn or from 2-collar (V2) to 10-collar (V10) corn, whichever is the most restrictive. Status use rates range between five to 10 oz/A, higher use rates will make replanting more restrictive. Status requires the use of a NIS, COC, or methylated (MSO) + AMS (2.5 lb/A). Status provides excellent control of common lambsquarters, pigweed, common and giant ragweed and smartweed. Status contains dicamba, so special precautions need to be taken to avoid vapor and particle drift. Do not apply Status if temperatures exceed 85°F.

Soybeans (p. 48-84)

Formulation changes, label changes, new premixtures and one new active ingredient are some of the changes to the soybean section. This year in the market place there are new formulations of Harmony, Express and Harmony Extra. This is important because along with these new formulations there will still be the old formulations in the market. The new formulations will all be soluble granules (SG) and will be referred to as TotalSol formulations. The new formulation of Harmony (thifensulfuron) is Harmony TotalSol 50SG which is a 50 percent formulation. This formulation is replacing the 75 percent XP formulation of Harmony GT. The new formulation for Express XP (tribenuron) is Express TotalSol 50SG and the new formulation of Harmony Extra XP (thifensulfuron + tribenuron) is Harmony Extra TotalSol 50SG. The use rates for the new formulations are 1.5-times the applications rates of the old formulations. For example, if you applied 0.08 (1/12) oz/A of Harmony 75XP, you would now use 0.12 (1/8) oz/A of the new TotalSol formulation of Harmony 50SG. If you used 0.33 oz/A of Express 75XP in the past, you would now use 0.5 oz/A of Express TotalSol 50SG. Finally, if you used 0.6 oz/A of Harmony Extra 75XP, you would now use 0.9 oz/A of Harmony Extra TotalSol 50SG.

Unity 75DF is a new product marketed by Gowan Company. Unity is a similar formulation of thifensulfuron as the old formulation of Harmony GT. Therefore, the typical use rate for Unity 75DF is 0.08 (1/12) oz/A and it should be applied with NIS and AMS.

Although Canopy EX 29.5DG is not a new herbicide to the soybean market, recent label changes will allow for it to be used differently than it has in the past. Canopy EX is a premixture of Classic (chlorimuron) plus Express (tribenuron) that has been typically used in the fall or early spring (45 d prior to planting) for control of winter annual weeds and residual control of certain summer annual weeds. Canopy EX can now be applied within 7 days of planting soybean if the use rate is 2.2 oz/A or less and can be applied within 14 days of planting with use rates of 2.2 to 3.3 oz/A. As with all chlorimuron products, use rates and rotational restrictions are dependent on soil pH.

Authority MTZ 45DF (p.54 and 70) is a new premixture of Spartan (sulfentrazone) and Sencor (metribuzin) marketed by FMC Corporation. Authority MTZ can be applied in the fall, early preplant, preplant or preemergence. The application rate of Authority MTZ depends on its intended use. Authority MTZ can be used from eight to 12 oz/A as a foundation treatment prior to glyphosate in glyphosate-resistant soybean or at higher rates up to 20 oz/A for longer residual weed control. At the higher rates, chances of soybean injury are greater and certain soybean varieties have been found to be sensitive to the active ingredients in Authority MTZ. Consult your local seed provider about varietal sensitivities. Authority MTZ at the 10 oz/A rate contains 3.6 oz/A of Spartan and 3.6 oz/A of Sencor. Authority MTZ will provide control of some winter annual weeds and provides residual control of common lambsquarters, eastern black nightshade, pigweeds, smartweed, velvetleaf, common ragweed and horseweed (marestail). Authority MTZ should not be applied to emerged soybeans. Rotation restrictions and precautions for Authority MTZ are similar to restrictions for Spartan and Sencor.

Valor XLT 40.3DG (p. 55 and 72) is a new premixture marketed by Valent Agricultural Products. Valor XLT contains Valor (flumioxazin) and Classic (chlorimuron) and can be applied in the fall, early preplant, preplant or preemergence. The typical use rate of Valor XLT is 3 oz/A (1.76 oz/A of Valor and 1.24 oz/A of Classic), unless the soil pH is greater than 6.8. If the soil is pH ranges from 6.9 to 7.6, Valor XLT should only be applied at 2.5 oz/A or less. Do not use Valor XLT if soil pH is greater than 7.6. Valor XLT will provide control of some winter annual weeds and provides residual control of common lambsquarters, common ragweed, eastern black nightshade, pigweeds, smartweed, velvetleaf, wild mustard, and horseweed (marestail). Valor XLT should not be applied to emerged soybeans and should not be tank-mixed with chloroacetamide containing products like: s-metolachlor (Dual Magnum), dimethenamid-P (Outlook), alachlor (Intrro), or flufenacet (Define) or severe soybean injury can occur. Rotation restrictions and precautions for Valor XLT are similar to restrictions for Valor and other chlorimuron containing products.

Envive 41.3DG (p. 55 and 72) is a new premixture marketed by DuPont. Envive is similar to Valor XLT in that it contains Valor (flumioxazin) and Classic (chlorimuron); however Envive also contains the herbicide Harmony (thifensulfuron). Envive can be applied in the fall, early preplant, preplant or preemergence. The typical use rate of Envive is 3.5 oz/A (2 oz/A of Valor, 1.28 oz/A of Classic, and 0.208 oz/A of Harmony SG), unless the soil pH is greater than 7.0. If the soil pH ranges from 7.1 to 7.6, Envive should only be applied at 2.5 oz/A or less. Do not use Envive if soil pH is greater than 7.6. Envive will provide control of some winter annual weeds and provides residual control of common lambsquarters, common ragweed, eastern black nightshade, pigweeds, smartweed, velvetleaf, wild mustard, and horseweed (marestail). Envive should not be applied to emerged soybeans and should not be tank-mixed with chloroacetamide containing products like: s-metolachlor (Dual Magnum), dimethenamid-P (Outlook), alachlor (Intrro), or flufenacet (Define) or severe soybean injury can occur. Rotation restrictions and precautions for Envive are similar to restrictions for Valor, Harmony, and other chlorimuron containing products. Similar to Envive, DuPont also has a new product called Enlite 47.86DG. Enlite contains the same active ingredients as Envive, but has a lower ratio of chlorimuron (Classic) in the premixture. Envive will be the product predominately sold in Michigan.

Rage D-Tech 4.06EW (p. 70) is a new premixture that can be used as a burndown treatment prior to planting soybean. Rage D-Tech should be applied at 0.75 pt/A with a crop oil concentrate (COC) at one percent v/v and AMS, sevens days or more prior to planting. Do not plant soybean if the seven days interval has not been met. Rage D-Tech at 0.75 pt/A contains 0.82 fl oz/A of Aim and 0.78 pt/A for 2,4-D ester. More time is needed prior to planting soybean if the Rage D-Tech rate is increased.

ET 0.2L (p. 70) is a new herbicide marketed by Nichino America, Inc. that can be applied with glyphosate in a burndown application prior to planting soybean. ET (pyraflufen) is a new active ingredient used at rates from 0.5 to 2.0 fl oz/A. ET is a contact herbicide without residual activity and is only effective on broadleaf weeds. ET should be applied with a NIS or COC. Visual symptoms appear soon after ET application. ET is not a stand alone product and should be tank-mixed with glyphosate and/or 2,4-D ester. Do not apply to emerged soybean.

Autumn 0.1 DG (p. 70) has received a label for fall only applications prior to planting soybean. Autumn (iodosulfuron) at 0.3 oz/A will control existing vegetation of certain weeds and provide some residual weed control. Autumn requires the addition of COC and AMS for effective control. Tank-mixtures with 2,4-D ester or glyphosate are recommended to improve control of existing weeds.

Small grains (p. 85-97)

One new herbicide active ingredient was added to the small grains section. The active ingredient pinoxaden is in the products Axial 0.83L and Axial XL 0.42L. The difference between these two products is that Axial XL has a built-in adjuvant and Axial needs to be applied with the adjuvant Adigor at 9.6 fl oz/A. These herbicides are primarily used for grass control in wheat and therefore probably do not have much of a fit on most of our wheat acres. However, in areas where windgrass is a problem, Axial or Axial XL would be an option for control. Axial and Axial XL can be applied to wheat at the 2-leaf to pre-boot stages. Weeds should be actively growing and at the 1-to-5-leaf stage. The use rate for Axial is 8.2 fl oz/A, and the rate for Axial XL is 16.4 oz/A. In the printing of the 2008 Weed Control Guide, there was an error in the ratings of Axial and Axial XL on page 97. In this table, annual grass control should be rated as excellent (E) and field bindweed control should be rated as no control (N).

Dry edible beans (p. 109-117)

The major changes to the dry edible bean section include the addition of several new glyphosate formulations and Aim as preharvest options. Currently, there are several new glyphosate formulations labeled for preharvest applications in dry edible beans. Consult product labels for legal applications and remember that glyphosate should only be used to control weeds prior to harvest, not as a desiccant. Glyphosate can only be applied when beans are in the hard dough stage (30 percent moisture or less).

Aim 1.9EW (p. 116) at 1 to 2 fl oz/A plus MSO at one percent v/v can be used as a preharvest treatment when the dry edible bean crop is mature. This means that at least 80 percent of the pods are yellowing and mostly ripe and no more than 40 percent (bush-type beans) or 30 percent (vine-type beans) of the leaves are still green. In our trials, Aim has not been as effective as glyphosate of Gramoxone Inteon. Dry beans cannot be harvested within seven days of application.

Potatoes (p. 118-125)

Similar to the dry bean section, the major changes in the potato section include additional options for vine desiccation. Aim 1.9EW (p. 124) at 3.2 fl oz/A with MSO, COC, or NIS can be used as a vine desiccant. Aim rates up to 5.8 fl oz/A can be used for desiccation and sequential applications may be needed. Do not apply more than 11.6 fl oz/A of Aim per year. In our trials, Aim has not been as effective as Reglone or Rely, and it is important to remember that potatoes cannot be harvested within seven days of application. Additionally, there is a new formulation of Rely 1L (glufosinate), Rely 200 1.67L. Rely 200 should be applied once at 29 fl oz/A. Do not harvest potatoes any sooner than nine days after Rely 200 application.

Sugar beets (p. 126-134)

A new section on weed control in Roundup Ready sugar beets was added to the guide. This section can be found on page 133 and outlines general recommendations, use rates and precautions for glyphosate use in Roundup Ready sugar beet.

Glyphosate formulations (p. 138-139)

This year there are several new glyphosate formulations that can be used in Roundup Ready (glyphosate-resistant) crops. The table on pages 138 and 139 contains a list of all products that were labeled for use in Michigan as of the printing of the 2008 Weed Control Guide. This table contains the manufacturer of the product, formulation, product equivalent rates, and whether a surfactant needs to be included for maximum weed control.

Dr. Sprague's work is funded in part by MSU's AgBioResearch.