NDSU Extension - Griggs County


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October 9

NDSU Extension Griggs County Column by Jeff Stachler

Corn silage is completed.  Corn grain harvest has begun.  Yields are coming in near the 150 bushels per acre mark and moistures are in the teens already!  Soybean and dry bean harvest is nearing completion, both are over 80% harvested.  Yields have been across the board from 20 to 50 bushels per acre. 

The freezing temperatures on September 8th and 9th killed many weed species, but not all.  Now is a good time to control biennial and cool-season perennials in pastures and rangeland.  Cool-season weeds that appear to have survived the freeze include leafy spurge, field bindweed, Canada thistle, the knapweeds, absinth wormwood and others.  If the weeds have green leaves and the growing point is still green as well, then herbicides can be applied to control these species.

To control field bindweed, apply Tordon 22K plus 2,4-D or Facet L plus Overdrive plus methylated seed oil.

To control diffuse and spotted knapweed and yellow starthistle apply dicamba plus nonionic surfactant, Tordon 22K, Tordon 22K plus 2,4-D ester, Plateau, or Milestone.  Plants in the rosette stage will be controlled most effectively.

Milestone can be applied as a spot treatment up to 14 fluid ounces per acre to dormant Russian knapweed plants for control.  Apply Plateau or Tordon 22K after several hard freezes around mid-October.  Plants may be dormant with a grey stem and no leaves and still be effective.  For control, Plateau must be applied at 12 fluid ounces per acre which will reduce grass production, so spot treatments are best.

The most cost-effective treatment to control leafy spurge in pastures and rangeland is Tordon 22K at 2 pint per acre plus 2,4-D ester at 2 pints per acre.  For best control of leafy spurge, plants need to be between 4 and 12 inches in height.  Other treatments providing some control of leafy spurge include dicamba at high rates plus oil adjuvants or Facet L plus Overdrive plus a methylated seed oil adjuvant.  Casoron 4 G or Norosac 10G can be applied in late November to early March before emergence for season long suppression.

To control Canada thistle apply Curtail, Stinger or Transline plus oil adjuvant, Overdrive plus a methylated seed oil adjuvant, chlorsulfuron plus metsulfuron plus an oil adjuvant, or Milestone.  Milestone is more effective in the fall than the spring.

To control bull, musk, or plumeless thistle apply 2,4-D, 2,4-D plus dicamba plus an oil adjuvant, chlorsulfuron plus metsulfuron plus an oil adjuvant, dicamba, Overdrive, Curtail, Milestone, Transline, or Tordon 22K.  Fall is the best time to control biennial weeds.

For control of dalmation toadflax apply Plateau at 12 fluid ounces per acre plus a methylated seed oil adjuvant after a hard freeze when 25 percent of foliage is necrotic.

To control absinth wormwood, hopefully you mowed the plants in mid-summer and allowed them to grow at least 12 inches before application this fall.  Herbicides that can provide effective control if plants are mowed and 12 inches tall include 2,4-D, dicamba plus an oil adjuvant, Curtail, Tordon 22K, and Milestone.

For herbicide rates and more information consult pages 73 to 88 in the 2020 North Dakota Weed Control Guide and herbicide labels for grazing restrictions and other information.

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