NDSU Crop and Pest Report
Weeds


ISSUE 5   June 3 2004

CAN ALL GLYPHOSATES BE APPLIED ON RUR CORN II?

There have been several calls about which brands of glyphosate that can be applied on RUR corn II hybrids. RUR corn II hybrids are new for 2004 and have increased resistance to glyphosate over the original RUR corn hybrids. There are only a few glyphosate brands that specifically mention and contain directions for use on RUR Corn II hybrids (NK603, Sprayflex), such as RU UltraMax, RU UltraMaxII, RU WeatherMax, Glyphomax, Glyphomax Plus. There may be others glyphosate brands labeled for use on RUR corn II.

Glyphosate brands allowing application RUR corn should be applied to RUR corn up to 30 inches or 8 collars at a maximum single application rate of 32 fl oz of a 3 lb ae/gal formulation or 22 fl oz of 4.5 lb ae/gal formulation. Glyphosate brands allowing application RUR corn II should be applied to RUR corn up to 24 inches or 8 collars but allows drop nozzle application to corn from 24 to 48 inches and applied at a maximum single application rate of 20 to 26 fl oz/A for annual weeds and up to 40 fl oz/A for perennial weeds for RU UltraMax or at 16 to 22 fl oz/A for annual weeds and up t 32 fl oz/A for perennial weeds for RU UltraMax II. See page 22 of the 2004 ND Weed Control Guide for additional information.

The question has been asked, can generic glyphosate brands that allow use on RUR corn be applied on RUR corn II hybrids even if directions for use on RUR corn II are not included in the label? After consultation with the ND DOA and Monsanto, there a combined agreement that any glyphosate brand labeled on RUR corn can be applied to RUR corn II hybrids but the application information and restrictions contained on the label must be followed. In summary, use glyphosate according to its label directions and not according a different glyphosate brand that may list other use directions.

 

HERBICIDE UPDATE PART III

Accent and Steadfast (DuPont)

Mode of action: ALS inhibitor
a.i.:
nicosulfuron / nicosulfuron + rimsulfuron
Crops: Corn.
Comments: Accent and Steadfast: Label recommends applications to corn less than 12 inches tall.

Spray Adjuvants - Use of nitrogen fertilizer-based adjuvants are not required if prohibited on tank mix partner labeling. This change was made to accommodate tank mixtures with Lumax herbicide, which prohibits nitrogen fertilizer.

Rates for MSO adjuvant were widened to include 0.5 % v/v. This change was made to accommodate the so-called MSO/OS adjuvants such as Dyne-Amic.

The prohibition against using MSO adjuvants with tank mixtures containing Callisto herbicide has been modified. Current Callisto labeling prohibits the use of MSO with postemergence rates of herbicide (3 oz). The proposed ACCENT label accommodates this prohibition, but authorizes the use of 0.5% v/v MSO when used in tank mixture with up to 1.5 oz Callisto.

Tank Mix Applications - Specific language recommending Lumax herbicide (S-metolachlor + mesotrione + atrazine) has been added for additional control of crabgrass section. The recommendation differs slightly from the generic recommendation for preemergence grass herbicides in that the rates are limited to no more than 2 pts of Lumax product (roughly 1/3 x labeled rate, equivalent rates = 11 oz Dual II Magnum, 2.1 oz Callisto, 4 oz atrazine), the nitrogen fertilizer requirement was dropped, and the height limit on corn is 5 inch maximum.

Crop Rotation Table - A separate crop rotation table has been prepared for ACCENT used at a maximum of 0.67 oz. Crop rotation intervals for alfalfa, red clover, potato, sunflower and canola have been changed to 10 months (with footnote qualifiers for cumulative moisture and geography). Since the original intervals were based on a total seasonal use rate of 1.0 oz. a.i. nicosulfuron, re-crop data for nicosulfuron was re-examined based on the label rate of 0.67 oz/A and re-crop data for Steadfast was re-examined based on a maximum use rate of 0.75 oz/A.

In addition, a footnote on the original 1.33 oz maximum use rate table was modified allowing 10 month rotation to sugarbeets at sites in MN south and east of the RR valley with soil pH <7.5 and a maximum use rate of 0.67 oz ACCENT. This change brings the label into agreement with existing language on the STEADFAST label.

Tank mixtures of Yukon herbicide (halosulfuron + dicamba) have been added for additional control of yellow nutsedge.

Define (Bayer)

Mode of action: Unknown
a.i.: flufenacet
Crops: Field, silage, and seed corn.
Comments: Reduced rates of both DF (6 to 12 oz/A) and SC (7.5 to 15 fl oz/A) formulations have been registered for POST application up to V5 stage (5 collars) but do not exceed a 75 day preharvest interval. This label allows POST application which is similar products like soil-applied herbicides like acetochlor (Surpass/Harness) 0 to 11 inch corn, alachlor (Lasso) 0 to 5 inch corn, dimethenamid-p (Outlook) 0 to 12 inch corn, pendamethalin (Prowl H2O) 0 to 30 inch corn, and s-metolachlor (0 to 40 inch corn.

The value of adding any one of these preemergence herbicides to a POST program is the residual activity to prevent/reduce other weed flushes. Non of these products will control emerged weeds when applied POST. If grass weeds have emerged, apply Define with POST grass products like Option or Steadfast to conventional corn or with Liberty on Liberty Link corn or with glyphosate on RUR corn. Yellow foxtail is a grass weed often missed by Accent, Steadfast, and Option if applied past the 2 or 3 inch stage. NDSU research has shown near complete and season long yellow foxtail control when Option at 1.5 oz/A was mixed and applied with Define at 8 to 9.6 oz/A + recommended adjuvants. Additional research is being conducted in 2004 to determine if the enhanced yellow foxtail control applies to Define applied with other POST grass herbicides and if other acetanilide herbicides improve grass control similar to Define. Apply early in postemergence programs to allow maximum control from the POST grass herbicide, to protect yield and avoid early season crop competition from heavy densities of grasses, and take advantage of the residual nature by controlling the additional flushes of grass that may emerge after application.

Equip (Bayer)

Mode of action: ALS inhibitor
a.i.:
foramsulfuron (Option) and iodosulfuron
Crops: Corn
Comments: Some may have seen advertisements for Equip in some ag magazines. Both ingredients are ALS inhibitors. While it may have national registration it is not being actively marketed in ND because of the long rotational crop restriction due to the iodosulfuron component. Alfalfa, potato, peas, beans, sunflower, sugarbeet, and other vegetable crops is 18 months.

Starane (Dow/UAP)

Mode of action: Plant growth regulator
a.i.: fluroxypyr
Crops: New registration on corn through the 5-leaf stage.
Comments: Dow has retained the rights to market the product. Apply 0.67 pt/A to labeled broadleaf weeds before 8 inches tall. No additional adjuvants are needed unless recommended by a tank-mix partner. Starane’s strength has been kochia control but also controls chickweed, cocklebur, purslane, ragweed, hemp dogbane and may suppress nightshade and wild buckwheat. See label for tank-mix options to improve broadleaf weed control. Starane is rain-fast within 1 hour.

WideMatch M (Dow)

Mode of action: Growth Regulator
a.i.:
Co-pack: WideMatch S = fluroxypyr (Starane) + WideMatch CM = clopyralid + MCPA (Curtail M). Contains 1.5 oz a.e. clopyralid, 1.5 oz fluroxypyr, and 8 oz a.e. MCPA. Co-pack contains 1.4 gallon of WideMatch S and 5 gallons of WideMatch CM which treats 22.4 acres/case = 8.15 fl oz/A of WideMatch S and 29 fl oz/A of WideMatch CM or 0.9 qt of Curtail M and 0.5 pt of Starane.
Crops: Wheat, durum, barley, oat.
Comments: A transition product available only in 2004 and will be replaced by WideMatch in 2005. Controls a wide spectrum of weeds including wild buckwheat, winter annual mustards, Canada thistle, cocklebur, dandelion, vol. flax, kochia, lambsquarters, common mallow, redroot pigweed, prickly lettuce, Russian thistle, smartweed species, sunflower, and biennial wormwood. Perennial sowthistle and field bindweed are suppressed. Apply to small grains at the 3-leaf stage to flag leaf emergence and to annual weeds less than 4 inches tall. May be tankmixed with Puma, Discover, Everest, and Achieve. Observe follow crop rotation restrictions. Cost approximately $9.00/A

WideMatch (Dow)

Mode of action: Growth Regulator
a.i.:
fluroxypyr (Starane) at 1.5 oz a.e./A +clopyralid (Stinger) at 1.5 oz a.e/A or 1 pt/A product use rate.
Crops: ND state registration 5/14/04 in wheat, durum, barley, oat and corn.
Comments: Apply to small grains at the 3-leaf stage to flag leaf emergence and to annual weeds less than 4 inches tall. Controls over 60 broadleaf weeds including seedling alfalfa, wild buckwheat, winter annual mustards, chickweed, clovers, Canada thistle, cocklebur, dandelion, vol. flax, horseweed, kochia, marshelder, nightshades, prickly lettuce, sunflower, and biennial wormwood. Perennial sowthistle and field bindweed are suppressed. Does not control some important broadleaf weeds like redroot pigweed, common lambsquarters, and lanceleaf sage. May be tankmixed with the following broadleaf herbcides to increase broadleaf weed control spectrum: MCPA, Harmony GT, Express, and 2,4-D. Observe follow crop rotation restrictions. Cost approximately $7.50 to $8.00/A but supply may be limited in 2004. Product is priced more competitively than mixing the products together. The active ingredients, clopyralid and fluroxypyr do not antagonize grass control from POST grass products (Puma, Discover, etc) labeled in wheat and barley. Do not plant pea, lentil, and potato until 18 months after application but most other crops can be planted the following year.

Richard Zollinger
NDSU Extension Weed Specialist
r.zollinger@ndsu.nodak.edu


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