Mistletoe

Around this time of year mistletoe is sometimes a popular decoration in people’s homes. You’ll see it hanging above doorways for use by romantically inclined couples. Nowadays you can buy plastic mistletoe at stores to put up in your house. Let’s talk about the effect that mistletoe can have on trees in the nature.

The origins of hanging mistletoe come from Norse mythology and Celtic Druids.

You can find mistletoe outside on trees year round as it is an evergreen plant. Usually in December it will become more noticeable because trees are bare after dropping their leaves. If you see a green bundle of leaves in the branches of tree around this time of year, chances are that it’s mistletoe. In the plant world mistletoe is considered a parasitic plant. Mistletoe will send its root, called the haustorium, into the bark of a host tree. The mistletoe will take nutrients and water from the host tree.

Mistletoe is usually found in the southern United States, because it is susceptible to freezing temperatures, ranging from Virginia over to Texas and down to Florida. It can infect more than 105 different species of trees. Some trees often infected by mistletoe are maples, buckeyes, birch, hickory, oaks, and a whole bunch more.

Mistletoe can be shaded out by surrounding branches. Therefore, fast growing trees that can cover mistletoe from above will have success in preventing infection. 

Mistletoe creates a large draw for water and nutrients on the tree. Mistletoe will pull these things to itself away from the roots of the tree. This process can lead to a lot of stress on the tree, especially in a drought. Mistletoe tissue will have 1.6 times more nitrogen, 2.3 times more potassium, and 2.5 times more phosphorus than the host tree tissue. During times of drought mistletoe water and nutrient uptake from the tree will increase while the rest of the tree is in decline. Research has shown that moderately infected trees can have a 66% mortality rate after a severe drought period. Mistletoe is able to pull water from the tree more effectively than the tree can pull the water up.

Mistletoe infections can be very common. Trees that are taller than surrounding trees and trees that are not densely packed in with other trees are most likely to be infected. Infections will be begin at the top of the tree and move downward and inward over time. Advanced symptoms on the tree of infection can be branch die-back, reduced tree growth, increased stress, and in massive infestations, tree death.

Early intervention is critical when dealing with mistletoe infection. If you simply remove the mistletoe shoot it will mostly likely grow back, so repeated removal would be necessary. Pruning tree branches that are infected is an effective method of removing mistletoe. Remove the branch at least 14 inches below the point of infection. Ethephon is as chemical application that is a plant growth regulator that can be used to control mistletoe. Whenever you apply any chemical, read the label before application. 

Control of mistletoe on old and socially significant trees can be important. Having a mistletoe infection does not necessarily mean that death is imminent for a tree, but mistletoe can have a drastic impact on the tree’s ability to thrive. If you have any questions about mistletoe contact your local Extension Office or email me at Jacob.Williams@uga.edu.