Drought affects musk thistle establishment
By Steve Young
UNL Extension Weeds Specialist
Drought can have a dramatic effect on musk thistle establishment in grazed and non-grazed perennial grasses, as seen in a two-year study conducted in west central Nebraska and completed in 2012.
In the wet year (2011), light availability (e.g., grazed treatments) was key in allowing musk thistle to establish. In the dry year (2012), water was most important in the establishment of musk thistle, regardless of how much light there was.
So, what does this mean? If, in a wet year, you overgraze a pasture with musk thistle, you’re going to create more problems—this is not really new information. The study offers more insight for musk thistle management in a dry year.
If you overgraze and graze early in what could be a dry year, you will help the established musk thistle become even more prolific and possibly allow newly germinating seedlings to develop into fully mature plants in less than five months. During this study we documented what most people know to be a biennial plant completing its life cycle in less than a year.
Finally, in drought conditions, growers might need to abandon grazing completely in areas of their fields where musk thistle is a current problem or known to occur. It is too risky to stress an established perennial grass pasture even more and create niches for musk thistle to establish, once conditions become favorable again.
For more information about musk thistle and its management in Nebraska, see the UNL Extension publication, Noxious Weeds of Nebraska: Musk Thistle (EC176) at www.ianrpubs.unl.edu/epublic/live/ec176/build/ec176.pdf.
Also see information on an upcoming field course being offered by UNL in June: the North American Invasive Plant Ecology and Management Short Course www.ipscourse.unl.edu as well as information on UNL’s Invasive Weed Ecology Program www.ipscourse.unl.edu/iwep.