General Impact
Zouhar (2001) reports that many environmental and economic losses have been attributed to C. diffusa infestations. Examples include replacing wildlife and livestock forage on rangeland and pasture, depleting soil and water resources, displacing native species on wildlands, reducing biodiversity, reducing land value, and disflavouring milk. Carpenter and Murray (Undated) state that C. diffusa is a pioneer species that can quickly invade disturbed and undisturbed grassland, shrubland, and riparian communities. Once established, it outcompetes and reduces the abundance of desirable native species. It contains the allelopathic chemical cnicin, which can suppress the growth of other species and allows it to grow in single-species stands. These stands can produce up to 40,000 seeds/sq m, which enables the infestation to proliferate rapidly. On rangeland, it is generally unpalatable to livestock, and the spines of C. diffusa may cause injury to the mouth and digestive tract of grazing animals. Infestations can greatly reduce dryland forage production with estimated losses of up to 88% in some areas. A 1979 report estimates that the annual loss from reduced grazing due to its infestation costs ranchers 80 cents per acre (NAPIS, 1993). Carpenter and Murray (Undated) report that on agricultural land, it can greatly reduce the value of hay and can decrease the value of the land. Other losses include soil erosion, and reductions in wildlife populations due to the decrease in forage production. In the North American Region it is a designated undesirable species in Colorado, a restricted noxious weed in Arizona, a candidate species for the New Mexico noxious weed list, and a designated weed species in Utah. It is listed as a noxious weed in British Columbia, Manitoba, and Ontario.
No Impact information recorded for Centaurea diffusa
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