Expansion of the invasive European mistetoe in California, USA

TitleExpansion of the invasive European mistetoe in California, USA
Publication TypeJournal Article
Year of Publication2020
AuthorsShaw, DS, Lee, CA
VolumeOn-line early
Date Published02/2020
KeywordsCalifornia, European mistletoe, introduction, invasive, Viscum album

The horticulturist Luther Burbank introduced the European mistletoe (Viscum album L.) to Sebastopol, Sonoma County, California, USA, around 1900 to grow as a Christmas ornament crop and tincture for medicinal use. The mistletoe has since spread from the point of introduction on apple to other hardwood trees, especially non-native hardwoods in yards and farms of the region. Mistletoe surveys were previously conducted in1971,1986, and 1991. We re-surveyed the region in 2019, with emphasis on the 1991 perimeter, and documented the current farthest distribution of V. album. This represents a 120-year record of spread. We observed infected trees up to 24.6km (15.3miles) from the point of introduction, doubling the farthest distance reported in 1991.Theestimated area encompassed by mistletoe-infected hosts increased from 184 km2 (71 miles2) in 1991 to 606 km2 (234 miles2) in 2019. We also updated the host species list including both native and non-native mistletoe hosts. Viscum album spread appears to be limited by available habitat and hosts, but within the survey area it is intensifying, concentrated in urban and semi-urban yards, streets, and farms. However, V. album was also commonly found in riparian areas, which have a large number of native hosts.