The rust species "Puccinia obtegens" has shown some promise for controlling Canada thistle, but it must be used in conjunction with other control measures to be effective. Also "Puccinia punctiformis" is used in North America and New Zealand in biological control. In 2013, in four countries in three continents, epidemics of systemic disease caused by this rust fungus could be routinely and easily established. The procedure for establishing this control agent involves three simple steps and is a long-term sustainable control solution that is free and does not involve herbicides. Plants systemically diseased with the rust gradually but surely die. Reductions in thistle density were estimated, in 10 sites in the U.S., Greece, and Russia, to average 43%, 64%, and 81% by 18, 30, and 42 months, respectively, after a single application of spores of the fungus.