Small Broomrape (Orobanche minor) in Oregon and the 3 Rs: Regulation, Research, and Reality

Abstract

Small broomrape is a federally listed noxious weed that was first identified in Oregon in 1923. Between 1923 and 1997, there were only six reports of the species in Oregon. Small broomrape is a holoparasitic weed that attaches to the root of its host and can lead to crop failure depending on the level of infestation. Small broomrape was identified in a red clover field in Oregon in 1998. In 2000 and 2001, the Oregon Department of Agriculture surveyed red and white clover fields in Oregon for the presence of small broomrape; 15 infested fields were identified in 2000 and 22 in 2001. The source of the small broomrape seed was not identified although there was speculation that small broomrape seed may have been contaminated clover seed stock. In 2000, a quarantine was established for small broomrape in red clover seed. Research identified effective, easy to implement management strategies for small broomrape including the use of false host crops and imazamox. In 2003, the ODA amended the quarantine to eliminate the mandatory seed sampling and testing and the requirement of reporting infested fields and seed lots. In 2011, there are still populations of small broomrape present in red clover fields in Oregon.