Individual study: Creeping thistles can be systemically infected with the rust fungus Puccinia punctiformis using weevils in Switzerland
Wandeler H., Nentwig W. & Bacher S. (2008) Establishing systemic rust infections in Cirsium arvense in the field. Biocontrol Science and Technology, 18, 209-214
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Control weeds without damaging other plants in conservation areas
A replicated, controlled, randomized study in 2004-2005 in a former agricultural field near Bern, Germany (Wandeler et al. 2008) found that creeping thistle Cirsium arvense could be infected with a systemic rust fungus Puccinia punctiformis using the weevil Ceratapion onopordi as a disease carrier. There was a significantly higher rust incidence within 1 m of weevil-treated thistle shoots (34 shoots infected) compared to controls (1 infected). Overall, within a radius of 1 m, 27% of weevil-treated shoots had rust infections compared to 3% of control shoots. There was no significant effect of the treatment within radii of 0.3 m or above 1 m. Therefore, rust infections could be induced between 0.3-1 m from weevil-treated thistles. The field had been sown with a mixture of wildflower seeds, grass and clover Trifolium spp.. In April 2004, 60 thistle shoots (? 1 m apart) in the wildflower strip were randomly assigned as either infected (with one female weevil powdered with rust spores (1000 spores/female)), or controls. Weevils were confined to shoots for 72 hours using a cylinder sealed at the top; controls received only the cylinder. Systemically infected thistles were located and assigned to the nearest experimental shoot, within radii of 0.3, 1, 2 or 3 m in April-July 2005.