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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #35815


item Bruckart, William - Bill
item Politis, D
item Defago G
item Rosenthal, S
item Supkoff D M

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: Musk thistle is a serious weed that was introduced into the United States from Europe. In the United States, it is a weed of ranges and pastures, particularly in the West. We can make the plant sick with a disease (caused by a rust fungus called Puccinia carduorum) present on the weed in its native Turkey. In an earlier study, we found that the pathogen also infected artichokes and a few American thistles but caused no damage. We tested these other plants in a special containment greenhouse and in Switzerland to make sure it will not damage these other American plants. In these tests, we learned that the amount of infection on plants other than musk thistle was not enough to damage them or allow us to keep the pathogen alive. We decided from this information that the pathogen was all right to use to control musk thistle in the United States

Technical Abstract: Susceptibility of 16 accessions of Carduus thoermeri (the target weed), 10 accessions of related weedy Carduus spp., 22 native and 2 introduced weedy Cirsium species, and Cynara scolymus (artichoke) to Puccinia carduorum from Turkey was measured in greenhouse and field tests. C. thoermeri was very susceptible in all tests, as were putative hybrids between C. thoermeri and other large-flowered Carduus spp. Disease incidence on C. nutans or C. macrocephalus was between 0 to 5% of plants inoculated. Of 454 individual Cirsium thistles inoculated, 83% did not develop symptoms immune, including all individuals in 11 species. For the Cirsium species in which symptoms were observed, 75% of the individuals were immune when inoculated 4-5 wk after planting, and no susceptible reactions developed after reinoculation of these individuals 2 wk later. A similar effect of plant age and susceptibility was noted for C. scolymus. Results similar to those in the greenhouse occurred in field inoculation of eight selected Cirsium spp., 2 Cynara spp., and 3 Carduus spp. in Switzerland. Results support the concept of host specificity reported for P. carduorum in the literature and in field tests conducted in Virginia