Leafy mistletoe (Phoradendron serotinum) is a familiar sight on oaks and other hardwoods throughout our area, especially in the winter when our deciduous hardwoods are leafless. Oaks, maples, flowering pear, pecan and other hardwoods are commonly infected. In all, over a 100 species of native and introduced trees can serve as hosts for mistletoe.
The scientific name, Phorodendron, literally means ‘tree thief’ in Greek. Mistletoe is an evergreen perennial plant that steals water, minerals, and food from the host tree. The fruit is typically white, with a hard seed covered by a glue-like pulp. Mistletoe is spread primarily by birds that feed on the mature berries. The seed remains viable even after passing through the digestive tract of a bird. Following germination, specialized structures are produced that mechanically penetrate the bark and wood of the branch producing the root-like structures called haustoria that tap into the tree to steal water and nutrients, just like a tick feeding on your dog.
While mistletoe won’t often kill the tree, it affects the long-term health and structure of infected trees. And during severe drought events like we experienced in 2016, mistletoe can put host trees under additional stress as they extract water from their host.
The number of the mistletoe clumps will typically increase over time as birds spread the sticky seed or feed on the berries and deposit the droppings throughout infected trees. The following pictures show how mistletoe increased in a tree over seven-year period.
Controlling Leafy Mistletoe
The best way to control mistletoe on landscape trees is to prune out the mistletoe clumps. Prune at least one foot below the point of attachment of the mistletoe. Cutting closer than a foot risks leaving some of the mistletoe haustoria inside the branch which usually will result in it growing back. If the clump is growing from the main stem or branch you don’t want to remove, another option is to remove the green mistletoe stems and leafy shoots. While this won’t kill the mistletoe plant it will stop it from stealing water from the tree until new shoots grow back. But, it may take a year or two for it to return. Removing a few clumps this winter can help make your tree healthier in the long run and stop the ‘tree thief’ from stealing from your tree.
By Jim Jacobi, Extension Plant Pathology Specialist, Alabama Cooperative Extension System. Contact Jim at firstname.lastname@example.org.
The Alabama Cooperative Extension System (ACES) operates as the primary outreach organization for the land-grant functions of Alabama A&M and Auburn Universities. ACES is committed to affirmative action, equal opportunity and the diversity of its workforce. Educational programs of ACES serve all people regardless of race, color, age, sex, religion, disability, sexual orientation, or national origin.