DiTomaso (2001) states that due to the spiny nature of the plant, livestock and wildlife avoid grazing in heavily infested areas. Thus, infestations can greatly increase the cost of managing livestock. In addition to rangeland, pastures and grasslands, C. solstitialis is also an important weed problem along roadsides and an occasional problem in dryland cereals, orchards, vineyards, cultivated crops, and wastelands (Maddox et al. 1985, in DiTomaso, 2001). It can also reduce land value and reduce access to recreational areas (DiTomaso et al. 1998, Roché and Roché 1988, in DiTomaso, 2001). In addition, C. solstitialis infestations can reduce wildlife habitat, displace native plants, and decrease native plant and animal diversity (Sheley and Larson 1994, in DiTomaso, 2001). Because of its high water usage, C. solstitialis threatens both human economic interests as well as native plant ecosystems (Dudley 2000, in DiTomaso, 2001). Although no economic assessments have been conducted for C. solstitialis, millions of dollars in losses probably occur from interference with livestock grazing and forage harvesting procedures, producing lower yield and forage quality of rangelands (Callihan et al. 1982, Roché and Roché 1988, in DiTomaso, 2001). DiTomaso (2001) states that when ingested by horses, it causes a neurological disorder of the brain called nigropallidal encephalomalacia or "chewing disease." Continued feeding results in brain lesions and ulcers in the mouth (Kingsbury 1964, in DiTomaso, 2001). In most cases, poisoning destroys the animal’s ability to chew and swallow and death occurs through starvation or dehydration (Panter 1991, in DiTomaso, 2001). DiTomaso (2001) states that only horses are affected by ingesting C. solstitialis. Other animals, including mules and burros, are not susceptible to the toxic effect of the weed.
No Impact information recorded for Centaurea solstitialis