46 



3. WEED CONTROL ACTIVITIES: Weed control activities 

 could pose a problem especially to the roadside 

 populations at Elk Lake (002) and French Creek 

 (003) , and managers should be made of aware of 

 population locations. 



B. MANAGEMENT PRACTICES AND RESPONSE: A weevil introduced 

 as a biological control for Carduus species (introduced 

 Eurasian species) , has a high infection rate in 

 populations of the endemic thistle Cirsium lonqistylum 

 in the Little Belt Mountains of north-central Montana. 

 The introduced weevil is lowering the fecundity of C. 

 lonqistylum populations. This same weevil is also 

 known to infect a number of other thistles in 

 California, including C. brevistylum , another species 

 of concern in Montana (Turner 1987b) . The possibility 

 of this occurring with other native thistles should be 

 taken into account when considering introduction 

 biological controls. 



C. RECOMMENDATIONS FOR MAINTAINING VIABLE POPULATIONS: It 

 is recommended that managers be made aware of the C. 

 subniveum populations with respect to any weed control 

 activities scheduled for these areas. Also, this 

 species should be considered when evaluating the 

 impacts of proposed mining activities. 



D. RECOMMENDATIONS FOR FURTHER ASSESSMENT: Currently, 

 there are three known locations for C. subniveum in 

 Montana. All three sites should be resurveyed to gain 

 population information, and an inventory of areas that 

 contain potential habitat for the species should be 

 initiated. Information from the inventory would 

 provide information on the range of the species in 

 Montana, and improve our knowledge of its presence on 

 National Forest lands. 



E. SUMMARY 



There are currently three locations for C. subniveum in 

 southwestern Montana. Two of the populations (Elk Lake 

 (002) and French Creek (003)) occur in Beaverhead 

 County on lands managed by the Beaverhead National 

 Forest. A third population (Laurin Canyon (001)) 

 occurs in Madison County, on lands managed by the 

 Bureau of Land Management. A collection from French 

 Creek (003) (just north and west of Argenta, Montana) 

 was identified by A. Cronquist in 1991 as C. subniveum . 

 The French Creek (003) population is in a historic 

 mining district that has had some renewed attention by 

 geological interests in recent years. Land managers 

 should take this population into consideration whenever 

 evaluating activities that might affect the site. 



