NDSU Crop and Pest Report
Weeds


ISSUE 6   June 10, 2004

HERBICIDE UPDATE IV

Discontinued Products:

Many products are no longer being manufactured and will be sold until existing supplies are depleted. Some discontinued products are Axiom, Eradicane, Far-Go, Buckle, Fallowmaster, Muster, Ramrod, Rodeo, RU Custom, Readymaster ATZ, Storm, Tough.

Beyond (BASF)

Mode of action: ALS inhibitor
a.i.:
imazamox / imazapyr
Crops: Clearfield canola, wheat, and sunflower

Comments: Clearfield winter wheat is available since 2002 but Clearfield spring wheat is still under development and will not be available until 2005 or 2006.

Clearfield canola lines with value-added output traits (Nexera = Natreon quality oil varieties) and non-GM herbicide tolerance developed by a BASF/Dow agreement.

Clearfield sunflower is available from several seed companies.

Express (DuPont)

Mode of action: ALS inhibitor
a.i.:
tribenuron
Crops: Express resistant sunflower.
Comments: Non-GMO. DuPont has elected to reallocate the resources initially designated for additional field development work with Express Resistant (ER) sunflower to other projects. DuPont will support the IR-4 registration submission for Express registration on ER sunflower. ER sunflower is projected to be launched in 2005 but limited seed may be available.

Glyphosate (Monsanto/Several)

Mode of action: EPSP synthase Inhibitor
a.i.:
glyphosate
Crops: Preharvest in field pea, chickpea, lentil, and flax
Comments: Not all glyphosate formulation are registered for preharvest application in specified crops. See the 2004 ND Weed Control Guide for products that have been registered in ND for this use or go to the ND DOA web site at:

http://www.kellysolutions.com/nd

Spread of Glyphosate-Resistant Horseweed (Marestail) Widens In Ohio And Indiana. Ohio State University (OSU) researchers and Purdue University confirmed glyphosate-resistant horseweed in their states Suspecting that herbicide resistance has spread, researchers are now testing weed samples from 16 additional counties. Ten states are now reporting glyphosate-resistant horseweed infestations. According to recent university researcher estimates, more than 2.3 million acres are now infested with glyphosate-resistant horseweed in the United States. The spread of glyphosate resistance reduces the attractiveness of the Roundup Ready (RR) crop system. Horseweed is a common weed found in many no-till fields in ND. With the registered uses of glyphosate on RUR corn, soybean, and canola, and preharvest application in wheat, ND growers should keep a sharp eye on the watch for resistance developing. If it has happened in the mid-west it could happen here. This is a justification NOT reducing rates and either rotating or tank-mixing with herbicides of other modes of action. As a great weed scientist once said (John Nalewaja) "If you kill every weed in the field then resistance will never happen" or something to that effect.

Poast (BASF)

Mode of action: ACCase Inhibitor
a.i.: sethoxydim
Crops: Buckwheat and safflower.
Comments: Poast has been registered on buckwheat and safflower. PHI for buckwheat is 21 days.

Reflex (Syngenta)

Mode of action: PPO Inhibitor
a.i.: fomesafen
Crops: dry beans
Comments: 2004 Section 18 has been approved for ND and MN. See 2004 ND Weed Guide for more information.

Sandea (Gowan/Monsanto)

Mode of action: ALS inhibitor
a.i.: halosulfuron
Crops: Labeled in corn by Monsanto as Permit.
Labeled as Sandea by Gowan in dry beans, potato, veg crops.
Comments: Registration pending in dry beans, potato, and some vegetable crops. Also labeled in turf as Manage. Excellent control of large-seeded broadleaf weeds. Will leave a residue in the soil - follow crop rotation restrictions. Longest carryover at pH 7. Breakdown increases as pH increases or decreases from 7.

Select/Prism (Valent/AGSCO)

Mode of action: ACCase Inhibitor
a.i.: clethodim
Crops: Various.
Comments:
Canola = PHI reduced from 75 to 70 days and maximum rate/A increased from 5 to 6 fl oz/A.
Flax = PHI reduced from 75 to 60 days and maximum rate increased from 4 to 8 fl oz/A and maximum use rate/season from 5 to 16 fl oz/A.
Mustard seed = PHI reduced from 75 to 70 days and maximum rate/A increased from 5 to 6 fl oz/A and maximum use rate/season from 5 to 16 fl oz/A.
Alfalfa = Minimum rate/A for perennial grass control increased from 8 to 10 fl oz/A.
Volunteer corn = growth stage revised according to Select rate and adjuvant section revised when applied with glyphosate formulations.

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


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