English daisy (Bellis perennis, family Asteraceae) is a flowering plant native to Europe. It is widely used as an ornamental in North America but is also a weed in lawns in the western and eastern United States. In December 2000, plants growing in urban landscapes in Monterey County, CA, were infected with rust. Orange aecia containing aeciospores that measured 14 to 18 × 12.5 to 15 μm developed profusely on leaves. Severely diseased leaves wilted and collapsed. Other spore states (pycnia, uredosori, and telia) were not observed. Based on the size and ornamentation of the aeciospores, reduced white peridium, apperance of the peridial cells, and arrangement of sori, we identified the pathogen as Puccinia lagenophorae Cooke (1,3), a rust fungus native to Australia and New Zealand that since 1960 has been introduced to other continents (2). On English daisy, the disease has been reported only in Australia and Europe (1). The pathogen also occurs on numerous other plants of the subfamily Asteroideae (family Asteraceae) (2). The occurrence of P. lagenophorae on English daisy follows the recent, first-time detection of the same pathogen on common groundsel (Senecio vulgaris) in California (3). To test cross infectivity, a spore suspension of a rust isolate from common groundsel was prepared and applied to various ornamental plants known to be hosts of P. lagenophorae. Inoculated plants were kept in a humidity chamber for 48 h, then maintained in a greenhouse. After 9 to 14 days, aecia developed on English daisy, cineraria (S. cruentus), and common groundsel but did not develop on dusty miller (S. cineraria) or pot marigold (Calendula officinalis). In addition, a single telium, surrounded by aecia, was observed on one of the infected English daisy plants. The telium contained two-celled teliospores that measured 31 to 36.5 × 16 to 19 (-22) μm and one-celled mesospores that measured 22 to 34 × 13.5 to 16 μm. At point of attachment, the widths of the stalks measured 7 to 8.5 (-9.5) μm. Some of the spores had surface ridges. The morphological features of the telio- and mesospores agree with those described for P. lagenophorae. To the authors' knowledge, this is the first record of a rust fungus on English daisy in North America. The inoculation experiments indicated that the rusts on English daisy and common groundsel are not biologically separated, casting doubt on the taxonomic concept of Weber et al. (4) that considered the rust on English daisy to be a distinct species, P. distincta McAlpine (although they did not examine type material of either P. lagenophorae or P. distincta).
References: (1) M. Scholler. Sydowia 49:174, 1997. (2) M. Scholler. J. Plant Dis. Prot. 105:239, 1998. (3) M. Scholler and S. T. Koike. Plant Dis. 85:335, 2001. (4) R. W. S. Weber et al. Mycol. Res. 102:1227, 1998.