Invasive plants to look for after the flood
Extension Educator, Panhandle Extension District
Nebraska Extension Publications has a number of publications on thistle management and other invasive species at https://extensionpubs.unl.edu/. Search “thistle” or “invasive.”
The Nebraska Department of Agriculture has an excellent weed identification book, “Weeds of the Great Plains” at http://www.nda.nebraska.gov/forms/nw11.pdf.
Early Detection and Rapid Response is a concept to identify potentially invasive species prior to or just as the establishment of the invasive is taking place. An Integrated Pest Management plan can be developed to manage, contain and eradicate the invasive species before it can spread further. This will avoid costly, long-term control efforts.
The devastation Nebraska has experienced these past few months is unimaginable. Communities and people’s lives have changed forever. Though not the highest priority, one item that should be addressed in the near future is the chance that invasive plants may show up in areas that have never had them before.
Landowners should be aware of this potential problem and be ready to act should the situation arise. Invasive plants move in the environment by several ways, including wind, water and forage stocks. With the extensive flooding that has taken place, it is very possible that seed and plant parts from these plants have moved considerable distances to new areas in the pastures, farm ground and riparian sites. The forages generously shared by producers from other states could also contain other invasive plants not seen in this area.
Invasive weeds to watch for:
Listed below are some of the more invasive weed species that landowners should be looking for on their property. A short description given for each, with web links for more detailed information.
Canada thistle, Cirsium arvense L., perennial, reproduces by seed and rhizomes, non-native.
Musk thistle, Carduus nutans L., Biennial, reproduces by seed, non-native.
Bull thistle, Cirsium vulgare, biennial, reproduces by seed, non-native.
Scotch thistle, Onopordum acanthium L., biennial, reproduces by seed, non-native.
Plumeless thistle, Carduus acanthoides L., biennial, reproduces by seed, non-native.
Russian knapweed, Acroptilon repens, perennial, reproduces by seed and rhizomes, non-native.
Spotted knapweed, Centaurea maculosa auct., biennial, reproduces by seed, non-native.
Diffuse knapweed, Centaurea diffusa, annual or biennial or short-lived perennial, reproduces by seed, non-native.
Purple loosestrife, Lythrum salicaria L., perennial, reproduces by seed and rhizomes, non-native.
Phragmites, Phragmites australis, perennial, reproduces by seed, rhizomes and stolons, non-native.
Absinth wormwood, Artemisia absinthium, perennial, reproduces by seed and short roots, non-native
Prevention is the best and cheapest management option. Scout and monitor your land for any new plants that have not been there before. If you cannot identify the plants, contact your local Nebraska Extension Educator or local Nebraska Weed Control Authority to help with this.
It is best to control these plants during the early stages of growth. Do not let them become established, as control and maintenance of these plants will become more costly and time-consuming. Management of seed production is the key to keep these plants from spreading. Several different management options may need to be utilized to manage these weeds.
Perennial plants are best managed early in their growth stage before they become established. Some perennial plants and most biennial plants are usually managed in during the rosette stage in the fall, after a frost. Mowing can be done but will have to be repeated for the regrowth. Mowing will not kill the plants. Mowing plants with visible seed heads will not prevent seed production.
Chemical treatment should follow the mowing to prevent seed formation. Numerous chemical treatment options are available to manage these weeds. Products containing aminopyralid, clopyralid, chlorsulfuron, dicamba, metsulfuron, picloram (Restricted Use), triclopyr, glyphosate (non-selective) and 2,4-D have been shown to work. Tank mixes of several of these compounds may provide better control. The addition of a non-ionic surfactant to the herbicide mix will aid in control. Re-treatment may be necessary.
Be sure to select a product labeled for the site and the weed. Read, understand and follow all label instructions when using any pesticide.