THE EFFECT OF TEMPERATURE ON INFECTION OF CANADA THISTLE BY PUCCINIA PUNCTIFORMIS AND THE INFLUENCE OF INFECTION AND MOISTURE AVAILABILITY ON REPRODUCTION IN CANADA THISTLE

Abstract

The effects of soil moisture and infection by Puccinia punctiformis on vegetative reproduction of male and female clones of Canada thistle (Cirsium arvense) were investigated. As soil moisture stress increased, survival and vegetative reproduction of female clones decreased. Male clones were less susceptible to moisture stress than female clones. Infection by P. punctiformis affected Canada thistle flowering and decreased vegetative reproduction. The effect of temperature on infection of Canada thistle by P. punctiformis was also determined. Infection was most successful when Canada thistle roots were stored at 5, 10, or 15 C following inoculation. Temperature treatments prior to inoculation did not affect infection. Although gender did affect moisture tolerance, it did not affect susceptibility to P. punctiformis. Inoculating Canada thistle roots with P. punctiformis and exposing them to low temperatures may provide an effective way to infest stands of Canada thistle in the field.