Effects of mistletoe (Phoradendron villosum) on California oaks

Walter D. Koenig*, Johannes M.H. Knops, William J. Carmen, Mario B. Pesendorfer, Janis L. Dickinson

*Corresponding author for this work

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Mistletoes are a widespread group of plants often considered to be hemipar-asitic, having detrimental effects on growth and survival of their hosts. We studied the effects of the Pacific mistletoe, Phoradendron villosum, a member of a largely autotrophic genus, on three species of deciduous California oaks. We found no effects of mistletoe presence on radial growth or survivorship and detected a significant positive relationship between mistletoe and acorn production. This latter result is potentially explained by the tendency of P. villosum to be present on larger trees growing in nitrogen-rich soils or, alternatively, by a preference for healthy, acorn-producing trees by birds that potentially disperse mistletoe. Our results indicate that the negative consequences of Phoradendron presence on their hosts are negligible-this species resembles an epiphyte more than a parasite-and outweighed by the important ecosystem services mistletoe provides.

Original languageEnglish
Article number20180240
JournalBiology Letters
Issue number6
Publication statusPublished - 2018
Externally publishedYes


  • Acorn production
  • Mistletoe
  • Phoradendron
  • Quercus

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