scholarly journals The Effect of Targeted Grazing and Biological Control on Yellow Starthistle (Centaurea solstitialis) in Canyon Grasslands of Idaho

2008 ◽  
Vol 61 (3) ◽  
pp. 314-320 ◽  
Author(s):  
John M. Wallace ◽  
Linda M. Wilson ◽  
Karen L. Launchbaugh
Keyword(s):  
Biological Control ◽  
Centaurea Solstitialis ◽  
Yellow Starthistle ◽  
Targeted Grazing

Late-Season Targeted Grazing of Yellow Starthistle (Centaurea solstitialis) with Goats in Idaho

2010 ◽  
Vol 3 (2) ◽  
pp. 148-154 ◽  
Author(s):  
Brianna J. Goehring ◽  
Karen L. Launchbaugh ◽  
Linda M. Wilson
Keyword(s):  
Canopy Cover ◽  
Centaurea Solstitialis ◽  
Yellow Starthistle ◽  
Late Season ◽  
Targeted Grazing ◽  
Goat Grazing ◽  
Plant Densities ◽  
Winter Annual ◽  
Landscape Scales ◽  
Grassland Site

AbstractYellow starthistle (Centaurea solstitialis) is an exotic winter annual forb that is aggressively invasive and problematic in much of California, Idaho, Oregon, and Washington. Yellow starthistle control is particularly challenging in canyon rangelands where accessibility limits control options. Our objective was to evaluate the effects of late-season targeted goat grazing on yellow starthistle and nontarget grasses and forbs. A 3-yr grazing study was initiated in 2006 on a 380-ha (939 acres) canyon grassland site infested with yellow starthistle near White Bird, ID. Twenty-four paired plots were established, with each pair including a fenced subplot to exclude grazing and a similar-sized adjacent subplot that was grazed. Density of yellow starthistle plants and seedheads was assessed after grazing of each plot in all 3 yr and before grazing in the second and third years. Canopy cover of yellow starthistle, grasses, and forbs also was measured. Grazed subplots had 58% fewer yellow starthistle plants than the ungrazed controls after grazing was applied and 94% fewer seedheads after 3 yr of grazing. Cover of yellow starthistle did not differ between grazed and ungrazed subplots after grazing in 2006, whereas grazing decreased yellow starthistle cover in 2007 and 2008 by about 75%. Goat grazing had little impact on canopy cover of grasses and resident forbs, with the exception of after grazing in 2007 when there was less forb cover in grazed areas compared with ungrazed areas. Late-season (i.e., July to November) targeted goat grazing appears to be an effective way to reduce yellow starthistle plant densities at landscape scales, which creates a large window of opportunity for grazing treatment and flexibility for land and livestock managers.

Biological Control of Yellow Starthistle (Centaurea solstitialis) in the Salmon River Canyon of Idaho

2010 ◽  
Vol 3 (4) ◽  
pp. 462-469 ◽  
Author(s):  
Jennifer L. Birdsall ◽  
George P. Markin
Keyword(s):  
Biological Control ◽  
Control Program ◽  
Centaurea Solstitialis ◽  
Biological Control Agents ◽  
Yellow Starthistle ◽  
Vegetation Monitoring ◽  
Salmon River ◽  
The Past ◽  
Insect Populations

AbstractYellow starthistle is an invasive, annual, spiny forb that, for the past 30 yr has been steadily advancing up the Salmon River Canyon in west central Idaho. In 1994, a decision was made to attempt to manage yellow starthistle by establishing a complex of biological control agents in a containment zone where the weed was most dense. Between 1995 and 1997, six species of seedhead-attacking insects were introduced and successfully established. By 1999, the insects had spread through the entire containment zone. Following this dispersal, a rapid buildup of insect populations occurred, and, since 2003, seed destruction has fluctuated around 90%. Vegetation monitoring plots, however, have shown no consistent decline in the overall population of yellow starthistle, indicating that the amount of seed produced is still sufficient to allow full replacement. However, county weed control personnel, who are responsible for surveying and destroying outlying populations of yellow starthistle beyond the containment zone, report that, during this period, the number of new, isolated pockets of yellow starthistle they are finding has dropped dramatically. This case study discusses how the biological control program partially met the objective of managing yellow starthistle by reducing the rate of advance of this weed in the Salmon River Canyon.

Chaetorellia australis(Diptera: Tephritidae) for biological control of yellow starthistle,Centaurea solstitialis(Compositae), in the western USA: establishment and seed destruction

1996 ◽  
Vol 86 (2) ◽  
pp. 177-182 ◽  
Author(s):  
C.E. Turner ◽  
G.L. Piper ◽  
E.M. Coombs
Keyword(s):  
Biological Control ◽  
Centaurea Solstitialis ◽  
Yellow Starthistle ◽  
Invasive Weed ◽  
Western Usa ◽  
Centaurea Cyanus ◽  
Field Samples ◽  
Initial Release ◽  
The Usa ◽  
Chaetorellia Australis

AbstractYellow starthistle (Centaurea solstitialisLinnaeus) (Compositae), native to Eurasia and the Mediterranean Basin, is a spiny and poisonous, naturalized, invasive weed of grasslands and other environments in the western USA.Chaetorellia australisHering is a trivoltine natural enemy of yellow starthistle whose larvae feed on developing seeds within capitula. Following host-specificity studies in Greece and the USA,C. australiswas first introduced from Greece into the USA in 1988 for the biological control of yellow starthistle. Field samples of yellow starthistle capitula revealed that 10.3% (four years after initial release) and 18.0% (three years after initial release) of capitula at Colfax, Washington, and Merlin, Oregon, respectively, were infested by ≥ 1C. australis(mature larvae or empty puparia). Both sites also contained naturalized, weedy populations of,Centaurea cyanus, a second host-plant ofChaetorellia australis. The fly was also recovered fromCentaurea cyanuscapitula two years after its release at Kendrick, Idaho. The potential importance of the presence ofC. cyanusforChaetorellia australisand biological control of yellow starthistle is discussed. At the Colfax site, all infested yellow starthistle capitula contained 1C. australis, while at the Merlin site 28.8% of infested capitula contained > 1C. australis, with a mean of 1.36C. australisper infested capitulum. A preliminary seed destruction impact study at the Merlin site showed that there was a 83.4% reduction in seeds per capitulum infested by ≥ 1C. australis, and the presence of > 1C. australisresulted in a 95.4% reduction in seeds per infested capitulum.

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