(PRWEB) April 30, 2013
Flea beetle proves to be a successful weed control agent in North Dakota grasslands
More than a decade ago, researchers introduced the leafy spurge flea beetle into North Dakota grasslands as a biological control agent for leafy spurge, a widespread invasive weed. An article in the journal Invasive Plant Science and Management indicates the approach is working, though it also seems to have had some unintended negative consequences.
The study examined both aboveground leafy spurge plant density and seedbank composition, and shows a significant reduction of both has occurred since the release of the flea beetle in 1999. The research, conducted over a 10-year period, included 24 study sites in the Little Missouri National Grasslands in western North Dakota and two types of ecological sites: loamy overflow and loamy. With the help of the flea beetle, leafy spurge has been successfully managed in both ecosystems.
To understand the historical and future composition of aboveground vegetation, a look at the soil belowground is necessary. The soil seedbank within an ecosystem can help land managers determine what actions they should take to improve the quality of a landscape.
After 10 years, the plant density decreased by 98 percent in loamy overflow sites and 89 percent in loamy sites. In the loamy overflow seedbank, leafy spurge seed was reduced by 96 percent, representing a change from 3,358 seedlings in an area of 0.5 m-2 in 1999 to just 127 seedlings in 2009. After constituting about 70 percent of the seedbank in 1999, it represented only 2 percent in 2009. The loamy sites also saw a reduction, from 1,429 seedlings per 0.5 m-2 in 1999 to 146 seedlings in 2009, about a 90 percent drop.
Unfortunately, the results of the flea beetle introduction have not all been positive. The successful effort against leafy spurge is tempered by a 250 percent increase in the density of another weed, Kentucky bluegrass. The absence of leafy spurge left an opening for the spread of this non-native perennial grass. Wet weather conditions in the later years of the study were also very favorable to Kentucky bluegrass.
Researchers also noted that although numbers of native plant species have increased over the course of the study, their re-establishment has been slow. Reseeding the native species once the invading leafy spurge began to decline could have helped precipitate the dispersion of native species and slowed the intrusion of Kentucky bluegrass.
Full text of the article “Change in Leafy Spurge (Euphorbia esula) Density and Soil Seedbank Composition 10 Years following Release of Aphthona spp. Biological Control Agents,” Invasive Plant Science and Management, Vol. 6, No. 1, January-March 2013, is available at http://www.wssajournals.org/
About Invasive Plant Science and Management
Invasive Plant Science and Management is a broad-based journal that focuses on invasive plant species. It is published by the Weed Science Society of America, a non-profit professional society that promotes research, education, and extension outreach activities related to weeds; provides science-based information to the public and policy makers; and fosters awareness of weeds and their impacts on managed and natural ecosystems. For more information, visit http://www.wssa.net/.
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