What is an invasive species? Executive Order 13112 defines an invasive species as a species that is “non-native (or alien) to the ecosystem under consideration and where introduction causes or is likely to cause economic or environmental harm to human health.” Invasive species can be plants, animals, or other organisms. Invasives may have one or more of the following characteristics:
A number of alien or introduced plant species occur in Kansas. Not all of these species are invasive. Some of the species that have become a problem in Kansas rangeland include: musk thistle, sericea lespedeza, Old World Bluestems, and saltcedar.
Musk thistle (Carduus nutans) was first reported in Kansas in 1932. By 1963, musk thistle was declared as a noxious weed throughout Kansas. Today, musk thistle infests about 900,000 acres in Kansas. Musk thistle is primarily a biennial or winter annual, reproducing only by seed. A single plant can produce in excess of 10,000 seeds. Scattered plants can be removed mechanically by digging below the crown. Other options for control include biological and herbicide application. The musk thistle head weevil, Rhinocyllus conicus, and the rosette weevil, Trichosirocalus horridus, have been released in Kansas to help reduce seed production. Musk thistle is easily controlled by herbicides if treated during the rosette stage. Commonly used herbicides on rangeland and pasture, such as 2,4-D, dicamba (Banvel), metsulfuron (e.g. Escort XP), and picloram (e.g. Tordon 22K), used alone or in combination can provide good to excellent control. Further information on identification and control of musk thistle can be found at http://www.ksre.ksu.edu/bookstore/pubs/L231.pdf.
Figure 1. Musk thistle rosette. Photos courtesy of Walt Fick, K-State Research and Extension.
Figure 2. Musk thistle in bloom.
Sericea lespedeza (Lespedeza cuneata) has probably been in Kansas since the 1930s. An herbaceous, perennial legume, sericea lespedeza is used as a forage crop in the southeastern United States and for mine land reclamation. As such, sericea lespedeza is a federally listed forage crop. However, the species’ invasive nature led to a declaration as a county option noxious weed in Kansas in 1988 and as a statewide noxious weed in 2000. An estimated 700,000 acres in Kansas are infested with sericea lespedeza. A high condensed tannin concentration in sericea lespedeza generally makes the plant unpalatable to grazing cattle. Sheep and goats are not affected by the tannin and graze sericea readily in the mid- and late-summer. Recent research by Dr. KC Olson and his students in the Department of Animal Sciences and Industry at Kansas State University has demonstrated increased utilization of sericea lespedeza by cattle when the animals are supplemented with corn steep liquor. Herbicides containing triclopyr (e.g. Remedy Ultra, PastureGard HL) or metsulfuron (e.g. Escort XP, Chaparral, Cimarron Plus) can provide control of sericea lespedeza for 1-3 years. After a period of time, sericea populations seem to recover from old crowns and/or a tremendous seedbank. Further information on sericea lespedeza can be found at http://www.ksre.ksu.edu/bookstore/pubs/mf2408.pdf.
Figure 3. Sericea lespedeza in bloom.
Old World Bluestems (OWB) including Caucasian bluestem (Bothriochloa bladhii) and yellow bluestem (Bothriochloa ischaemum) are scattered around the state and are increasing. These species were planted during the “soil bank” period in the late 1950s and 1960s. Today, we have OWB invading rangeland in Kansas. These species are commonly seen along roadsides in the state. Old World Bluestems are perennial warm-season grasses, just like the majority of native grasses that dominate our rangelands in Kansas. As a forage crop, OWBs can be burned, fertilized, and stocked heavily. The problem has been that OWBs won’t stay where they have been planted. Compared to our native, warm-season grasses, OWBs are lower in quality and mature more rapidly. Selectively removing an invasive grass like OWB from our rangelands will be difficult. Research conducted by Dr. Keith Harmoney at the Western Kansas Agricultural Research Center-Hays, me, and others in the region have concentrated on the use of glyphosate (e.g. Roundup) and imazapyr (e.g. Arsenal). Both of these herbicides are non-selective, especially at high rates. Imazapyr may provide some selectivity, but more research is needed. At this time, patches of OWB that have invaded rangeland should be treated with glyphosate or imazapyr to prevent seed production.
Figure 4. Rangeland invaded with Caucasian bluestem.
Figure 5. Caucasian bluestem.
Saltcedar (Tamarix ramosissima) is an invasive tree along streams and rivers in Kansas. More than 56,000 acres are infested with saltcedar along the Arkansas and Cimarron rivers. Saltcedar has also been identified along the Republican, Smoky Hill, and Kansas rivers. Unlike red cedar, saltcedar is a deciduous tree. It does have needle-like leaves. Saltcedar was first introduced into the U.S. in the 1850s. Originally, saltcedar was used as an ornamental, for wind breaks, and for erosion control along stream banks. Once established, saltcedar modifies the plant community by cycling salt to the soil surface. Grasses like salt grass and alkali sacaton coexist with saltcedar. The trees use about 80 gallons of water per day. Cutting or burning saltcedar results in prolific resprouting. Applications of herbicides on cut-stumps or basal treatments can effectively control saltcedar. Triclopyr (e.g. Remedy Ultra) and imazapyr (e.g. Arsenal) are effective cut-stump treatments and triclopyr applied in diesel can be applied as a basal treatment. The most effective foliar treatments for saltcedar control are imazapyr and glyphosate used alone or in combination. The non-selective nature of glyphosate and imazapyr may require renovation of sites broadcast or aerially sprayed with these herbicides.
Figure 6. Saltcedar in bloom.
Figure 7. Saltcedar in Cimarron River basin.
Learn to recognize these and other invasive species in Kansas. If a plant species shows up and starts to spread, get it identified. Unwanted species are easier to control when they first show up than later when they have taken over.
Walt Fick, Range Management Specialist