The genus Orobanche includes chlorophyll-lacking root parasites that parasitize many dicotyledonous species and cause severe damage to vegetable and field crops worldwide. In the United States, small broomrape is a federally listed noxious weed that has been found in red clover seed production fields in Oregon. In this study, we classified the susceptibility of red clover, white clover, and crimson clover to small broomrape infection under controlled conditions. Red, white, and crimson clover seeds were sown in pots containing small broomrape–inoculated soil. Differences in susceptibility to infection were observed among clover species; red clover was severely infected, white clover was slightly infected, and crimson clover was not infected.
Nomenclature: Small broomrape, Orobanche minor J. E. Smith. # ORAMI; crimson clover, Trifolium incarnatum L. # TRFIN; red clover, Trifolium pratense L. # TRFPR; white clover, Trifolium repens L. # TRFRE.