PUCCINIA-PUNCTIFORMIS AFFECTS GROWTH AND REPRODUCTION OF CANADA THISTLE (CIRSIUM-ARVENSE)

In growth chamber research, infection by Puccinia punctiformis, a rust fungus, reduced flowering and vegetative reproduction in Canada thist le. Disease symptoms were greatest when Canada thistle roots were stor ed at 5, 10, or 15 C following inoculation. Exposure of roots to diffe rent temperatures before inoculation did not affect disease. All Canad a thistle clones tested, regardless of gender became diseased although there were differences in susceptibility to P. punctiformis. Nomencla ture: Canada thistle, Cirsium arvense (L.) Scop. #3 CIRAR.