Developing Techniques for the Biological Control of Canada Thistle, Cirsium Arvense, Using the Obligate Biotroph Fungus, Puccinia Punctiformis.

Biological control is promising for noxious weeds, such as Canada thistle, Cirsium arvense.  Control of C. arvense, is extremely challenging and often requires integrated control efforts due to its perennial lifecycle and deep taproot.  This species, often found in crop fields, pastures, and rangelands, is detrimental to yields because it competes for water, nutrients, and light.  Efficient biological control technology may alleviate yearly costs of control.  Puccinia punctiformis, an obligate biotrophic fungus, is being investigated as a biological control for C. arvense.

Field experiments were conducted along Interstate 80 in central Pennsylvania to determine the spread of P. punctiformis throughout natural, healthy C. arvense patches.  C. arvense infected with P. punctiformis were transplanted from diseased highway patches into healthy roadside patches, and disease progress was recorded. 

A second study, plant survivability, was conducted at Rock Springs, Pennsylvania on greenhouse transplants and wild transplants to identify the best techniques for successfully transplanting diseased C. arvense.  The experiment evaluated the effects of pot size and soil moisture, through the use of a water retention gel, on the survivability of the host plant.

Results for experiments conducted along Interstate 80 are not conclusive at this time, but further monitoring may provide insight on the use of thistle infected with P. punctiformis to initiate epidemics in healthy patches.  Plant survivability results revealed pot size and soil moisture did not affect C. arvense lifespan.  New infections developed in the experimental plots, showing P. punctiformis spores from transplants do serve as infectious inoculums.  The results will contribute to refining the technique of transplanting P. punctiformis infected C. arvense for biological control of field patches.