Community Agriculture Alliance: Weed season will start early this year

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Spring 2012 could hardly be more different from spring 2011. The soil, weeds and seeds still lying under snow last year have been warming for weeks under our sunny skies. We can be pretty certain of cooler, cloudy weather, but this weed season is going to get off to a much earlier start.

Whitetop (hoary cress) is one of our earliest and most problematic noxious weeds. As a List B species under the Colorado Weed Law and as one of Routt County’s 13 noxious weeds, management and control efforts are required. The areas near Steamboat Springs and especially just west and southwest of town are seriously impacted by this perennial member of the mustard family. The Elk River Valley also is becoming increasingly affected. The plant has an extensive rhizome system and the flowers and leaves we can see are just the “tip of the iceberg.” Unless one is pulling, digging or hoeing first-year plants, mechanical controls are ineffective against whitetop. The plant also will continue to flower below mowing height. This weed is one that really does require herbicide for successful control. Spraying with chlorsulfuron at 1 ounce/acre or metsulfuron methyl at 1.5 ounces/acre is recommended. Always use an appropriate surfactant when spraying to increase herbicide effectiveness and shorten the rain fast interval.

Herbicide should be applied to young, actively growing plants. By the end of the flowering season, spraying is no longer effective. No matter what chemical you use, read the entire label. The label will contain the EPA registration number, signal word indicating relative toxicity, first aid for exposure, personal protective equipment requirements, re-entry interval for workers or residents, withdrawal periods for livestock or haying (if any) and recommended rates for different susceptible weeds. An insect, serving as a biological control agent, is currently under evaluation, but a public release is still a couple of years away.

Houndstongue also is a List B weed and one of Routt County’s 13 noxious weeds. This biennial weed produces multiple seed burs that cling to anything they touch, thus enabling widespread dispersal by us, our pets, livestock and wildlife. When you pick the seeds off you, your dog or your horse, don’t toss them on the ground. Bag them securely or run them through the wood stove. Houndstongue leaves are toxic to horses.

This year’s meager snowpack left a lot of last year’s dead plants standing, and they can serve as markers this spring to start control efforts. When you walk up to an old houndstongue plant, you will likely see many young rosettes. Pulling, hoeing or digging can eliminate these young rosettes, and you can spray the older, larger rosettes before flowers form. Chlorsulfuron and metsulfuron methyl also are recommended for houndstongue at the same rates indicated for whitetop.

These are two weeds we can work on early this season. Contact me at 970-870-5246 or gbrown@co.routt.co.us for questions about weed identification, management or herbicides.

Greg Brown is the supervisor of the Routt County Weed Program and a Community Agriculture Alliance board member.

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