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ISSUE 10   July 5, 2001



Preliminary research has shown good leafy spurge control for more than two years from a spring applied application of Tordon at 1 pt/A + 2,4-D amine at 1 qt/A + Plateau at 4 fl oz/A + MSO adjuvant at 1 qt/A + 28% N at 1 qt/A. However, research has shown that Plateau applied without other herbicides gives greater leafy spurge control when applied in late summer or early fall and the Section 18 directs the use as such. The question has arose is Plateau can be applied in the spring. Below is a clarification of the federal and Section 18 label for use of Plateau for leafy spurge control.

Federal label:

Allows use of Plateau in spring or fall at rates up to 12 fl oz/A on noncropland. Plateau can be applied to CRP (no grazing or haying) at a maximum rate of 4 fl oz/A. Plateau cannot be used on any area where grazing or haying will occur.

Label recommends for best results to apply in late summer or early fall (August through mid-October). However, spring applications are not prohibited.

ND Section Label:

Plateau may be applied to areas to be grazed or hayed such as pasture, rangeland and CRP at rates of 8 to 12 fl oz/A. NOTE: The Section label is effective from August 1 through December 31, 2001. Plateau cannot be applied before August 1 to any area to be hayed or grazed.

The spring application of Tordon + 2,4-D + Plateau + MSO adjuvant + 28% N can only be applied in noncropland! Treated areas cannot be hayed or grazed. Technically, spring applications made in noncrop areas can not be grazing indefinitely. BASF is seeking label amendment to allow grazing and/or haying but the registration has NOT been approved.

Plateau does not control Canada thistle.



The NRCS has issued notification to land owners of their responsibility to prevent spread of noxious weeds, including Canada thistle, in CRP. Some may choose multiple mowing/ clipping as a means to prevent seed formation because it is the least expensive option for the CRP to still be enrolled in the program. Mowing/clipping will not injure legumes where chemical application may injure or kill legumes. The NRCS has issued policy concerning control of noxious weeds in CRP and allow noxious weed control in grass/legume plantings. Refer to Paragraph T16 on page 109 of the 2001 ND Weed Control Guide for the policy. Mowing/clipping does absolutely nothing to kill roots or prevent underground root expansion. Despite mowing the root system may continue to increase in size within thistle patches.

A few strategies can be used to not only control top growth but also kill roots. These strategies will cost more but results will be much greater.

#1. Apply Redeem prior to thistle bud stage. Redeem contains two products one of which is clopyralid (Stinger) and cost approximately $65.00/gal. Rates range from 2.5 to 4 pts/A. NOTE: You get more clopyralid in Redeem for your dollar than any other product on the market, including Curtail or Curtail M. Cost is $20 to $32.50/A depending on rate.

#2. Use the Hunter Method or Rosette Method for Canada thistle control. Control thistle until the latter part of July when day length is less than 15 hours. See Paragraph T2 on page 107 of the 2001 ND Weed Guide for more information. Apply a relatively inexpensive but effective top growth control product like 2,4-D amine at 1 to 2 qt/A prior to thistle bud stage. 2,4-D controls top growth slowly. New shoots will emerge after day length is shorter than 15 hours but will not bolt but remain in the rosette stage. Apply Redeem to rosettes in late September or early October. Excellent root kill will result and thistle patches will controlled if not be greatly reduced in size. Followup application will be required in successive years. You cannot kill perennial weeds with one application of any herbicide - except maybe 2 gallons of Tordon/A.

#3. Some have asked if the Rosette method can be used with mowing/clipping. The strategy would include multiple clippings until late July then spray Redeem in late September or October. The key to making the Rosette Technique work is controlling ALL top growth until day length is shorter than 15 hours. When new growth emerges it senses short day length and will respond by not bolting. With mowing, bolted plants are clipped but basal leaves continue to sense day length. New growth emerging after late July are connected to plant roots that have been preconditioned by the long day length and established thistle patches may not respond to Redeem or other herbicide the same as using #2 above. Therefore, success may not be as great. NDSU does not have data to support these assumptions from clipping followed by herbicide application in CRP.

In short, clipping followed by herbicide application will give better control that just clipping alone. Any control strategy other than clipping and included with clipping is better than clipping alone. Wet years and mild winters continue to allow Canada thistle to increase in establishment and expansion of patch size. It appears Canada thistle has become one of ND worst weeds. Areas of little disturbance, like CRP, are fertile grounds for noxious weed establishment. However, land owners are also stewards of their land and should manage their land to prevent weed establishment that can infest surrounding areas. Your neighbors will certainly appreciate it.

Redeem does not control leafy spurge.



Absinth wormwood is a noxious weed of ND and requires control in CRP. Page 52 of the 2001 ND Weed Control Guide contain information for most effective control. The most cost effective treatment is 2,4-D at 2 qt/A. NOTE: Application should be made when plants are AT LEAST 12 inches tall and actively growing . Herbicides applied in late-June to mid-August have given greater residual control than spring or fall application. Plants can be mowed in early to mid-summer to promote active regrowth prior to fall treatment.

Richard Zollinger
NDSU Extension Weed Specialist


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