Phoradendron - Host and Symptoms

Host and Symptoms

Phoradendron species can infect many varieties of plants including Hackberry (Celtis spp.) mesquite, cedar, elm and Osage-orange. Certain species of Phoradendron infect specific plants; for example, in Arizona, Phoradendron tomentosum infects cottonwood (Populus fremontii), sycamore (Platanus wrightii), ash (Fraxinus spp.), walnut (Juglans spp.) and willow (Salix spp.). P. californicum infects shrubs and trees such as acacia (Acacia spp.) and blue verde (Cercidium floridum). Other Phoradendron species of the mistletoe also infect junipers (Juniperus spp.) and oak (Quercus spp.). Branches often become swollen and distorted, forming burls and making the tree more susceptible to insect attack. Phoradendron presents serious problems along rivers, streams, parks, and golf courses with large cottonwood trees, where mistletoe growing from the branches of an infected tree can be seen. Deciduous trees can be mistaken for evergreens during the winter if infection is heavy. Other common symptoms include swelling formations of witch's broom, dieback, and weakened branches.