The release and recovery of Bradyrrhoa gilveolella on rush skeletonweed in southern Idaho

Rush skeletonweed (Chondrilla juncea L.) is a major noxious weed in Idaho and other areas of the Pacific Northwest. A biological control program was implemented during the late 1970s in an attempt to manage infestations of rush skeletonweed and to limit its spread into new areas. Three agents, Cystiphora schmidti (Rubsaamen) (a gall midge), Aceria chondrillae (Canestrini) (a gall mite), and Puccinia chondrillina Bubak & Sydenham (a rust fungus) have been established in Idaho and other areas of the western United States. However these agents have provided only limited control of the weed. One additional agent, the root-feeding moth Bradyrrhoa gilveolella (Treitschke) (Lepidoptera, Pyralidae), was approved by the USDA-APHIS for release in the United States in 2002. Initial releases were made in southern Idaho in November 2002 and during the summers of 2003 through 2009 (excluding 2005). Releases were made using infested plants (the 2002 initial release) then utilizing first instar larvae and adults from greenhouse colonies. In total we released the moth at eight sites utilizing nine infested plants (est. 27 larvae), 6,095 larvae, and 60 adults. At several sites, releases were made in multiple years. Sites were periodically monitored for evidence of establishment (presence of adults or larval feeding tubes) during the summer or early autumn.