Community Agriculture Alliance: Spring weed management | SteamboatToday.com

Community Agriculture Alliance: Spring weed management

My weed management column has in the past discussed the legal and stewardship responsibilities for all land owners and managers to control their noxious weeds.  In this column, I will present weed control techniques for two of Routt County's noxious spring weeds.

One of our most troublesome noxious weeds, greening up as soon as the snow recedes, is houndstongue.  The burs that your dog has started bringing home contain the seeds for this Colorado List B noxious weed which is very toxic to livestock, especially horses.  The gray-green rosettes of this tap-rooted, biennial weed are quite obvious now and offer a great opportunity for control. 

Look first for the standing dead plants which may still hold last year's burs — pull or cut and bag these old plants — then search the ground for new plants.  Pull these young plants while the soil is still moist, dig the tougher plants, then walk in ever widening circles to look for more plants to pull, dig or bag. 

If your infestation is serious enough to warrant spraying, apply 1 1/2 ounce per acre of Escort or 1 quart per acre of 2,4-D, each with a non-ionic surfactant, to young actively growing plants.  Continue to monitor the infestation sites for new plants and pull, dig or spray as required.  Regular observation and diligent effort are key to houndstongue control.

Two bio-control insects used in Canada have been denied entry into the United States.  A native moth first observed defoliating houndstongue in the Yellowstone area is under evaluation in Idaho as a potential native bio-control.

Another serious List B weed problem in our county is whitetop, or hoary cress. Unlike houndstongue, whitetop is a strongly rhizomatous, long-lived, perennial that does not respond well to any form of mechanical control.  Any part of a root or rhizome left in the soil after trying to pull or dig the plants will generate a new plant and mowing induces the plants to form a shorter and denser weed cover.  Only recently germinated seedlings younger than six weeks, can be controlled by pulling. 

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Remember most of the emerging plants you will see this spring are sprouts from existing roots and rhizomes and will not pull but simply break off if you try to pull or dig them. Herbicide spraying should be done during May or early June when adequate leaf area is available for chemical absorption and before the bright white blossoms show any signs of fading.  The recommended herbicides are Escort at 1 1/2 ounce per acre or Telar at 1 ounce per acre, either to be used with a non-ionic surfactant.

When buying or using any herbicide always read and follow the label instructions exactly.  The labels and Safety Data Sheets for all herbicides are available online, so you have a chance to preview the use and safety aspects of any product you are considering purchasing. 

Contact The Routt County Weed Program at 970-870-5246 or gbrown@co.routt.co.us or CSU/Routt County Extension at 970-879-0825 or thagenbuch@co.routt.co.us with any questions about weed control.

Greg Brown is with the Routt County Weed Program.

Routt County Weed Program

136 Sixth Street

Steamboat Springs, CO 80487

P.O. Box 773598

Steamboat Springs, CO 80477

Email: weeds@co.routt.co.us

Phone: 970-870-5246

Fax: 970-879-3992