ISSUE 10   July 7, 2005


Several reports have been received of increasing acreage of houndstongue (Cynoglossum officinale L.), especially in western North Dakota. Houndstongue is a biennial which grows 1 to 4 feet tall and is a native of Asia. The name of the plant comes from the 6 to 12 inch long leaves which have prominent veins, are covered with a soft white pubescence, and feel rough, similar to a dog’s tongue. Houndstongue is commonly found in disturbed areas, along trails, and on the edge of wooded areas. Houndstongue seedlings emerge in early spring and summer and form a rosette. Plants bolt in mid-May to late-June of the second year. Purple flowers are borne on stalks 8 to 20 or more inches long. Each flower produces a nutlet of 3 to 4 seeds which are about 1/4 inch, oblong in shape, and covered with a hard husk with protruding spines. When mature, the brown nutlets break apart and stick to clothing and animals similar to burdock.

Houndstongue contains significant quantities of pyrrolizidine alkaloids which can induce fatal liver disease in grazing animals. As little as 15 mg/kg of dried plant material fed to horses (about 6% of a horse’s daily food intake) over a 2-week period was fatal. Cattle are also very susceptible to houndstongue poisoning while sheep are somewhat resistant.

Several herbicides are available to control houndstongue. First year plants (rosettes) can be controlled with 2,4_D applied at 1 lb/A (1 quart of a 4 pound per gallon concentrate) in late spring and early summer. Once houndstongue begins to bolt and flower Escort should be used because plants are no longer very susceptible to 2,4-D. Escort should be applied at 0.5 to 1 oz of product per acre with a surfactant. Escort will kill flowering houndstongue plants. Escort or Plateau at 8 oz/A plus an MSO can be used in the fall to control rosettes.

Rod Lym
NDSU Weed Scientist
Perennial/Noxious Weeds  



An excellent site showing herbicide symptomology by mode of action can be found at:



For some reason I have been getting several calls about a reported mistake about Harmony GT on soybean on page 23 of the 2005 ND Weed Control Guide. The rate listed is on page 23 is 3/10 to 6/10 oz/A. The in-crop use rate is 1/12 oz/A. Those that have brought this to my attention have failed to read the ‘When to Apply’ column - it is for preplant or ANYTIME PRIOR TO SOYBEAN EMERGENCE. For the in-crop listing of Harmony GT see the top of page 25.

Please read the guide carefully - I don’t need anymore stress in my life.



A ND Section 24c label has been approved allowing Durango brand herbicide of glyphosate to be applied preharvest in flax for weed desiccation. Not all glyphosate brands can be used for this use in flax. For a list of approved glyphosate brands in ND, see the Preharvest Application section on page 37 of the 2005 ND Weed Control Guide.



The Interactive Encyclopedia of North American Weeds - Version 3 DVD-ROM is available for purchase. Developed using a weed ID data base by the Southern Weed Science Society, the program was expanded and is available on a DVD. The Interactive Encyclopedia of North American Weeds - Version 3 DVD-ROM is a massive update to the "Weeds of the United States and Canada - Version 2/2.1 CD-ROM" released four years ago by the SWSS. The new DVD has been completely updated and resized from the older VGA (640 x 480 pixel) graphics to new high resolution XGA (1024 x 768 pixel) graphics. The program is now 2.3 Gb in size. All of the illustrations and photographs have been rebuilt and imported in higher color and higher resolutions. There are now over 2,300 photographs covering 447 of the most important weeds and crops in the United States and Canada. The illustrated glossary of 565 botanical terms is a program in itself! A unique illustrated interactive identification key now covers all of the weeds in the program. The professionally narrated lessons provide nearly three hours of interactive instruction on the basics of plant taxonomy needed to identify plants.

After 12 years of development, the program provides a balanced and fully integrated teaching and reference resource for weed, crop, and plant identification. The DVD-ROM is an excellent resource for teaching plant taxonomy and weed identification courses, basic botany, agronomy, and horticulture courses, and high school biology and vocational agriculture courses. A presentation maker feature allows an instructor or presenter create a custom path through the program. Professional agronomists, horticulturalists, groundskeepers, landscapers, turf managers, gardeners, herbalists, botanists, and all manner of plant enthusiasts will enjoy the extensive descriptions, distribution maps, habitat key, World of Weeds weed history articles, and the unique visual weed and crop identification key.

The Interactive Encyclopedia of North American Weeds - Version 3 DVD-ROM can be ordered through the NCWSS by clicking on the following link:

You can view a demonstration weed home page and obtain more information on the DVD-ROM at the following link:

Price is $59.95 each plus $5.00 shipping and handling in the US or $10.00 shipping and handling for international orders. If you already have a copy of Version 2 or 2.1, you can upgrade to Version 3 for $49.95 plus shipping and handling at the same address or phone number. You will need to mail the front cover of the insert booklet that came with Version 2 or 2.1 to verify the upgrade.

Richard Zollinger
NDSU Extension Weed Specialist

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