Host Range Determination of Puccinia jaceae from Yellow Starthistle. W. L. Bruckart, Research Plant Pathologist, U.S. Department of Agriculture, Agricultural Research Service, Foreign Disease-Weed Science Research Unit, Fort Detrick, Building 1301, Frederick, MD 21701. . Plant Dis. 73:155-160. Accepted for publication 24 August 1988. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/PD-73-0155.

Six rust fungus acquisitions from yellow starthistle (YST) were evaluated for biological control of YST in North America. Each acquisition (= field isolate) was identified as Puccinia jaceae on the basis of urediniospore morphology and host plant. All isolates caused limited infection of 12 plant species in the genera Carthamus, Centaurea, Cirsium, and Senecio under containment greenhouse conditions. Safflower inoculated with P. jaceae had only 5% as many pustules per square centimeter of leaf tissue as plants inoculated with P. carthami, the cause of safflower rust. Amounts of disease were much less on the other nontarget suscepts than on YST controls, except Centaurea cyanus, which was very susceptible. P. jaceae from YST is considered a good candidate for biological control of YST because of the limited infection occurring on a few nontarget species under conditions very favorable for infection of the intended target species.

Keyword(s): biological weed control, natural enemies, plant pathogen, Uredinales.