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ISSUE 15  August 15, 2002

 

CANADA THISTLE CONTROL

Canada thistle infestations become very obvious in mid-July and August. Dark green stems that were hiding in the crop or pasture now become all too obvious as the purple and rose colored flowers emerge. Many people want to treat Canada thistle in mid-summer, but that is probably the least effective application timing.

The best approach to Canada thistle control in cropland should include a herbicide treatment in crop to suppress Canada thistle growth, minimize crop yield losses, and prepare the thistle for a fall post-harvest treatment. Fall-applied treatments provide the most effective long-term control. The best herbicide to use will vary depending on crop rotation (See NDSU Extension Bulletin W-799 Perennial and Biennial Thistle Control). However, the control program must be uninterrupted for two to three years if the infestation is to be reduced.

Canada thistle growing in pasture and wild lands can be controlled with a variety of herbicides: Clopyralid plus 2,4-D (Curtail), picloram (Tordon), picloram plus 2,4-D amine, dicamba (Banvel), triclopyr plus clopyralid (Redeem), or 2,4-D. Control is greatest when applied in the fall to plants in the rosette growth stage. More herbicide (2 to 3 times) is translocated to the root system of Canada thistle when the treatments are applied to rosettes compared to bolted Canada thistle.

 

COST COMPARISON FOR CANADA THISTLE CONTROL

HERBICIDE

CLOPYRALID

COST/A

CONTROL

 

RATE OZ AI/A

 

12 MAT

REDEEM 2.7 PT

4

22

50

CURTAIL 5.3 PT

4

23

63

TRANSLINE 2/3 PT

4

27

87

STINGER 2/3 PT

4

40

87

STINGER 1/3 PT

2

20

90

TORDONa

8

21

100

aSEPARATE STUDY, GENERALLY 6 OZ/A WILL GIVE ABOUT 90% CONTROL.

**NOTE** - Research at North Dakota State University has shown that clopyralid alone will provide better Canada thistle control than when clopyralid is formulated with 2,4-D (Curtail) or triclopyr (Redeem). For instance, Redeem at 2.7 pt/A contains 4 oz/A of clopyralid, costs $22/A and provided 50% Canada thistle control 12 months after treatment, while clopyralid applied alone at 4 oz/A (Transline or Stinger) provided 87% control and cost $27 to $40/A depending on formulation.

Tordon may be the most cost-effective herbicide to use for Canada thistle control in pasture, rangeland, and non-crop. Tordon at 6 to 8 oz/A generally provides 90 to 100% Canada thistle control 1 year after treatment and costs $16 to $21/A. However, Tordon cannot be used in wet areas where Canada thistle is often found. Generally, Redeem or Stinger/Transline can be used near water.

 

TWO NEW ND NOXIOUS WEEDS

Roger Johnson, Agriculture Commissioner has proposed adding two weed species to the North Dakota State Noxious Weeds List: saltcedar (Tamarix ramosissima L.) and Dalmatian toadflax [Linaria genistifolia ssp. dalmatica (L)], using the North Dakota Administrative Code section 7-06-01-02 rule making process.

The addition of these two species will bring the number of State Noxious Weeds to twelve. The current list includes: absinth wormwood, Canada thistle, diffuse knapweed, field bindweed, leafy spurge, musk thistle, purple loosestrife, Russian knapweed, spotted knapweed, and yellow starthistle.

A copy of the Notice of Intent to Adopt Administrative Rules announcement, and a copy of the proposed rule amendment may be viewed as an attachment. The rule has also been posted at the North Dakota Department of Agriculture’s website:

http://www.agdepartment.com/

 

EPA PESTICIDE REREGISTRATION UPDATE

EPA has announced it has met the second phase of a three-stage, 10-year deadline to reassess nearly 10,000 pesticide tolerances. Under the Food Quality Protection Act of 1996, the agency had until August 3 to complete the comprehensive safety evaluation of 66% of pesticide tolerances that were in existence in August of 1996.

To date, the EPA has reassessed more than 6,400 tolerances for pesticide residues on food. As part of the reassessment process, EPA has revoked 1,900 tolerances. The agency also has reassessed nearly two-thirds of the tolerances for foods commonly eaten by children. On July 31, 2002 EPA completed its evaluation of four pesticides to comply with a consent agreement with the National Resources Defence Council (NRDC). These pesticides are: benomyl, diazinon, endosulfan, and lindane.

 

SUNFLOWER RUBBER?

ARS Plant Physiologists at Albany, California are experimenting with different types of sunflower that are adapted to the northern U.S. with the purpose of discovering lines that produce high amount of latex (rubber) in stem and leaves as opposed to flower heads. It is impractical to separate latex in the flower head from oil and other components.

Latex is made up of rubber and other particles surrounded by water and plant compounds and is a higher value product than solid rubber. As rubber factories of the future, sunflower could reduce dependence on imported natural rubber and on synthetic rubber made from petroleum.

More than 2,500 species produce natural latex but most are small, grow too slow, are not suitable for cultivation, and do not produce enough latex of high quality. Sunflower is an ideal crop for these qualities.

The quantity and quality of latex from sunflower is not sufficient for commercial use but researches are improving this through genetic engineering. Plant scientists are delineating the physical characteristics of sunflower candidates’ latex and comparing those of latex taken from two other natural sources - the Brazilian rubber tree and a desert shrub, guayule.

Researchers will insert laboratory-built genes for latex production into sunflower tissue, test for efficacy, identify those plants or lines that produce the highest amount of quality latex, and determine how to preserve the latex while in storage, awaiting processing.

The research is a joint project with colleagues from Colorado State University and Oregon State University.

 

HERBICIDE AD HALL OF SHAME

In perusing the web looking for timely material for the pest report I came across the web site for the Iowa State University Weed Science home page. Noticing interesting topics and good material, my eye caught a hot button named "Herbicide Ad Hall of Shame". My extension counterpart in IA, Bob Hartzler has made some interesting observations with some advertising material found in some ag magazines. If interested go to:

http://www.weeds.iastate.edu/weednews/adhallofshame.htm

Richard Zollinger
NDSU Extension Weed Specialist
rzolling@ndsuext.nodak.edu


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