European mistletoe (Viscum album) as well as American mistletoe (Phoradendron serotinum) are both evergreen parasitic perennials with white or translucent berries, that grow on the trunks and branches of deciduous trees. They are common holiday symbols sold frequently during the winter holiday season.
Mistletoe Toxic Components
Both mistletoe species are toxic to horses. P. serotinum contains phoratoxins which are toxalbumins that cause digestive upset. V. album contain viscotoxins, which are similar in structure and effect to the phoratoxin toxalbumins found in P. serotinum. V. album is more toxic then P. serotinum and ingestion of all parts other than the berries can result in toxicity of the liver, central nervous system, and kidney.
PHYSICAL CONTROL: In newly developed areas or in older established areas where trees are being replaced, the ideal method of controlling or preventing mistletoe is to plant trees believed to be resistant or moderately resistant to mistletoe.
For treatment of existing trees it is important to remove mistletoe before it produces seed and spreads to other limbs or trees. Mechanical control through pruning is the most effective method for removal. Growth regulators provide a degree of temporary control but repeated applications are required. Severely infested trees should be removed and replaced with less susceptible species to protect surrounding trees.