Extension Report

Baldwin County Extension Office

302A Byrne Street

Bay Minette, AL  36507

Telephone (251) 937-7176 or

928-0860/943-5061 ext. 2222

FAX (251) 937-7285

Beau Brodbeck

Regional Extension Agent

Forestry, Wildlife & Natural Resources

September 14, 2010

Is Mistletoe Harmful to My Trees?

Article Written By:

Beau Brodbeck

Alabama Cooperative Extension System

&

Gary Ickes

Ickes Tree Service

In the urban forest it is not uncommon to notice mistletoe growing in trees.  Mistletoe affects many species of trees in Alabama and can be an indicator of unhealthy trees that can lead to further tree decline and eventually death.  While there are two types of mistletoe in Alabama, the American or oak mistletoe (Phorandendron serotinum) is the most common in the Southern part of the State.   The most frequently affected trees by mistletoe are in the oak family, however, other species of hardwoods are also affected such as pecan, hackberry, cherry, sycamores and elms.  This article will outline factors that contribute to the occurrence of mistletoe and will provide some basic management and control recommendations.

Biology and Spread:

Mistletoe is a semi-parasitic plant that is commonly noticed during winter when deciduous hardwoods lose their leaves.   Mistletoe is evergreen, meaning that it retains its leaves year round and thus making it more noticeable during winter months.  The fruiting berries of mistletoe are spread to and within trees by gravity, wind, and birds.  Birds distribute the berries by passing the berries though their digestive system depositing droppings that germinates on susceptible hosts.

 Mistletoe grows by deriving its nutrients through a pseudo root system into the tree’s vascular system.  Mistletoe is considered semi-parasitic due to the plant containing its own chlorophyll.  However, mistletoe parasitizes trees by using its pseudo root to absorb minerals, nutrients, and water from host trees to produce sugars necessary for its growth through photosynthesis.

Damage:

Mistletoe generally grows on stressed and weakened trees.  The urban environment is a harsh place for trees to survive.  Urban soils are generally compacted, low in organic content and may contain a variety of foreign building materials that can change soil PH.  Additionally, trees in the urban environment are often subjected to regular root damage as a result of construction, trenching, sidewalks and other practices that cut and damage roots.

Initially mistletoe, especially in limited quantities, has minimal impacts on trees.  However, as mistletoe plants grow and begin to spread the depletion of water and nutrients will weaken the tree’s foliage.  When water and nutrients are reduced to the foliage, it causes an imbalance and the affected area weakens and dies. 

Trees rarely die as a result of mistletoe but rather due to secondary agents.  As the volume of mistletoe increases in the tree and the tree becomes increasingly stressed there are additional problems that develop.  Stress opens the tree to secondary diseases and/or pests such as Hypoxylon Canker or Ambrosia beetles.  The sooner mistletoe is treated the better the results.

Control:

The best method to protect trees from mistletoe is to manage and minimize stress.  The first step towards healthy trees and low incidents of mistletoe is stress management.   Good urban tree management begins by creating an environment that has soil with low compaction, proper levels of nutrients, minerals, organic matter, and water. 

In arboriculture, mulch and mulching around trees achieve many of these desired results with minimal costs and significant benefits towards overall tree health.  Apply mulch in a 3 inch thick layer being sure not to pile it on the trunk of the tree.  Mulch should extend a minimum of 3 feet in radius and to the drip-line of the tree if possible.

Once mistletoe becomes established in trees, the only viable option is manual removal.  A tree care company with an International Society of Arboriculture (ISA) Certified Arborist on staff should be contacted to remove the mistletoe and start to manage the tree’s stresses.  The amount of mistletoe, how long the mistletoe has been in the tree, and the amount of tree stress will determine the types and effects of treatment.  Treatment may not be suitable for all trees. 

An I.S.A. Certified Arborist should be able to determine whether to treat or remove the tree.  As with any company that works on private property, homeowners should always obtain certificates of insurance directly from the tree care company’s insurance agent and references. This will ensure that the individual has the proper insurances that protect homeowners from any accidents, injuries or damage to private property that may occur during the job.

For additional information contact your local Extension Office or visit www.aces.edu/ucf.

Email address: brodbam@auburn.edu

Phone: 937-7176 or 943-5061, ext. 2222

The Alabama Cooperative Extension System (Alabama A&M and Auburn Universities) in cooperation with the U.S. Department of Agriculture is an equal opportunity educator and employer.