First report of Puccinia glechomatis, a rust fungus of creeping charlie, in Minnesota

Authors: GREATENS, NICHOLAS - University Of Minnesota; KLEJESKI, NICK - University Of Minnesota; Szabo, Les; Jin, Yue; OLIVERA, PABLO - University Of Minnesota

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2023
Publication Date: 9/11/2023
Citation: Greatens, N.J., Klejeski, N., Szabo, L.J., Jin, Y., Olivera, P.D. 2023. First report of Puccinia glechomatis, a rust fungus of creeping charlie, in Minnesota. Plant Disease. First Report. Available: https://doi.org/10.1094/pdis-10-22-2315-pdn.
DOI: https://doi.org/10.1094/pdis-10-22-2315-pdn

Interpretive Summary: Creeping Charlie or ground ivy (Glechoma hederacea) is an invasive species of Eurasian origin and common weed of turfgrass, gardens, orchards, forests, and meadows that is widely distributed across North America and Southern Canada. It is well known by the public for its proliferation in home gardens and yards and its resistance to eradication. In 2020 and 2021, a rust fungus was observed on G. hederacea in the Twin Cities area. The disease caused partial leaf necrosis occurring with high foliar infection and leaf dieback with high stem infection. DNA sequence analyses showed a high homology with Puccinia glechomatis, a rust pathogen of G. hederacea. Morphological and life cycle traits are consistent with this identification. P. glechomatis was recorded for the first time in 1998 near Syracuse (NY), was found across the eastern U.S. and parts of the Pacific Northwest by the early 2000s. The fungus is not known to affect any native plants and may have a positive ecological effect, reducing the fitness of this undesirable, aggressive host plant. This report will be useful for horticulturists and home owners to monitor the spread and impact of the disease on this invasive plant.

Technical Abstract: Creeping Charlie or ground ivy (Glechoma hederacea) is an invasive species of Eurasian origin and common weed of turfgrass, gardens, orchards, forests, and meadows that is widely distributed across North America and Southern Canada. It is well known by the public for its proliferation in home gardens and yards and its resistance to eradication. In 2020 and 2021, a rust fungus was observed on G. hederacea. The disease caused partial leaf necrosis occurring with high foliar infection and leaf dieback with high stem infection. Thick walled dark teliospores and thin walled colorless leptospores, often pointed at apex, were produced. Some spores germinating readily without dormancy. In greenhouse inoculation experiments, teliospores from infected leaves were used as inoculum. Basidiospores were produced and reinfected G. hederacea. DNA sequence analyses of the EF1-a gene sequences showed a high homology (99.3% to 99.7%) with Puccinia glechomatis, a rust pathogen of G. hederacea. Morphological and life cycle traits are consistent with this identification. Puccinia glechomatis was recorded for the first time in 1998 near Syracuse (NY), was found across the eastern U.S. and in parts of the Pacific Northwest by the early 2000s. In 2001, its presence was recorded in southern Wisconsin. To our knowledge this is the first report of P. glechomatis in Minnesota. The fungus is not known to affect any native plants and may have a positive ecological effect, reducing the fitness of this undesirable, aggressive host plant.