ISSUE #496

496 - Use Roundup Wisely Today

3-28-07 

Herbicide tolerant corn and soybean use has occurred in Minnesota and North Dakota for years. The long awaited introduction of Roundup Ready sugarbeet is finally on the not so distant horizon. Its imperative sugarbeet growers use Roundup and the many generic glyphosate products with best weed resistance management practices possible. The same scenario experienced with Kochia that became resistant to Upbeet soon after it was labeled could occur with Roundup. Much better options are available in other rotational crops for weed control than are available for sugarbeets. Sugarbeet growers should take every precaution to prevent weed resistance from occurring in soybean and corn.

Weeds with Documented Resistance to Roundup

WeedYearLocation
Ryegrass 1998 California, Oregon
Horseweed (Marestail) 2000 Many states in East and North Central USA
Common Ragweed 2004 Missouri
Common Lambsquarters 2004 Ohio
Palmer Amaranth 2005 Southern USA
Waterhemp 2005 Missouri
Canada Fleabane 2005 Canada Prairie Provinces
Giant Ragweed 2006 Ohio, Indiana

Weeds Expressing Natural Tolerance to Glyphosate

Cinquefoil, Common Mallow, Clover, Kochia, Prickly Lettuce, Waterhemp, W. Buckwheat, Smartweed, Nightshade, Dandelion, Nutsedge, Velvetleaf

Strategies for Proper Roundup Use in Soybean and Corn – Alan Dexter, NDSU/U of MN Extension Sugarbeet Specialist

  • Use high glyphosate rates to slow weed resistance
  • 100% weed control should be the goal
  • Use cultivation and hand labor to control all escapes and prevent weed seed production
  • Always add NIS if the label allows it to maximize weed control.
  • Always add AMS to maximize weed control
  • Apply Roundup between 10:00 a.m. and 4:00 p.m. for best results
  • Use Liberty Link crops in your rotation if possible
  • Use conventional herbicides in your crop rotation to ensure Roundup effectiveness for your sugarbeets in the future
  • Use other “foundational” herbicides in conjunction with Roundup Ready crops

For More Information on Weed Resistance

  • See pages 106 – 107 in the 2007 North Dakota Weed Control Guide
  • Go to www.resistancefighter.com
  • Contact your Agriculturist, university specialist or crop consultant for assistance.

Strategies to Minimize Roundup Resistant Weed Development – R. Zollinger, NDSU Extension Weed Specialist

  • Scout fields regularly and identify weeds that escape and control them completely
  • Rotate herbicides with different modes of action in consecutive years
  • Apply herbicides in tank-mix, prepackage, or sequential mixtures that include multiple modes of action
  • Rotate crops with different life cycles; annual, biennial, perenial
  • Notify local extension agents, scientists or other consultants about suspected resistant weed development. They can test them to confirm resistance so eradication strategies can be implemented.

Maximize Weed Control with Soil Applied Nortron – Top 50 Do!
It’s very difficult to maximize weed control when Kochia or other difficult to control weeds are present without use of soil applied Nortron. Sixty percent of the top 50 grower group used soil applied Nortron in 2006.

Benefits of Nortron and Ethotron

  • Safest soil applied herbicide for beets in the Red River Valley
  • Good to excellent control of resistant Kochia and pigweed
  • Effective weed control for up to 10 weeks
  • Weeds that escape through banded Nortron are pre-conditioned for easier kill
  • Eliminates need for a layby herbicide
  • May reduce the need for one microrate application

Use Guidelines for Nortron and Ethotron

  • Heavy previous crop residue may reduce weed control
  • 0.5 to 0.75 inches of rain needed to fully activate the herbicide
  • Don’t cultivate close to beet rows, this may reduce weed control
  • Will control cover crop in the banded area
  • Best to rotate to beans or corn after use – carryover damage might occur to wheat
  • Can be tank mixed with Roundup at planting time

Cost Savings

  Cost
 RateBroad - Cast11" Band7" Band
Nortron/ Ethotron 7.5 pts $68 $34 $21
Nortron/ Ethotron 6 pts $55 $27 $17

Nortron cost used was $73/gallon.

Weed Resistance

Weed resistance cannot be prevented but it can be delayed. Every beet grower MUST make every effort to delay glyphosate resistant weed development as long as possible.

High Cost N

Reduce N fertilizer cost for 2007 by using N credits from 2006 beet tops. Maximize efficiency of N fertilizer using variable rate zone management in 2007. Contact your Agriculturist or crop consultant for assistance.