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Medusahead Spreads East

Montana State University recently confirmed the first observation of the invasive grass medusahead (Taeniatherium caput-medusae) in Montana. The species was collected in southeastern Sanders County, which is in the northeastern part of the state – fortunately relatively far from the Wyoming border. Currently, there are no known populations of meduasahead in Wyoming, but the Montana occurrence is a recent example of its continued spread. 

Medusahead is an introduced, annual, cool-season grass similar to cheatgrass in its growth habit as a winter annual but different in other ways. The seed heads have sharp appendages, known as awns, that may reach over 2.5 inches in length and may cause mouth or eye injury to livestock grazing in infested locations. Medusahead is reportedly very poor forage, partially because of high silica content in the leaves and stems. It can be highly competitive for nutrients and moisture and has been documented replacing stands of cheatgrass, especially in areas with heavy-textured soils. Given many of its characteristics, medusahead is likely much worse than cheatgrass for livestock producers.

Focus

Because we do not yet have medusahead, managers should focus on prevention and early detection and management of new infestations. 

It can be difficult to predict dispersal patterns of invasive plants, but the current progression has been an eastward movement from areas already infested. Idaho, Utah and now Montana have the species, so we should be increasingly aware of our susceptibility to it showing up here. The western counties of Wyoming most likely are at the highest risk of first noticing medusahead since large populations exist in Idaho and Utah. 

Disturbed sites with traffic from infested areas should be monitored diligently since they provide a good opportunity for both introduction and establishment. Industrial traffic, such as oil and gas operators, livestock movement and hay purchased from infested areas, may serve as potential means of transport for medusahead seed.

Invasion risk

As land managers, we can all keep an eye out for medusahead and be aware of the factors above that may increase a site’s risk to its invasion. 

Several common grasses, such as bottlebrush squirreltail or foxtail barley, may look similar to medusahead. An important distinction is that medusahead is an annual grass, so it should pull up relatively easily by the roots. 

I tend to think medusahead seed heads look like they have had a bad haircut. The bottom portion of the seed head has shorter appendages than the top once it matures. 

Watching for, and reporting any suspected populations of this problematic grassy weed to your local extension office, weed and pest district or to me directly can play a crucial role in implementing early-stage control actions that may limit the impacts of medusahead in Wyoming.

Brian A. Mealor is an Assistant Professor and Weed Extension Specialist at the University of Wyoming and can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..