Puccinia punctiformisAffects Growth and Reproduction of Canada Thistle (Cirsium arvense)

In growth chamber research, infection byPuccinia punctiformis, a rust fungus, reduced flowering and vegetative reproduction in Canada thistle. Disease symptoms were greatest when Canada thistle roots were stored at 5, 10, or 15 C following inoculation. Exposure of roots to different temperatures before inoculation did not affect disease. All Canada thistle clones tested, regardless of gender became diseased although there were differences in susceptibility toP. punctiformis.