Dwarf Mistletoe
(Arceuthobium spp.)
Dwarf Mistletoe is a small, leafless, natural parasitic flowering plant. It slowly weakens the trees and eventually kills them.
Dwarf Mistletoe grows only on branches and trunks of cone bearing trees. The parasite is identifiable when the yellow to green or brownish-green segmented shoots protrude from the infected part of the tree. The shoots are ½ inch to 6 inches long and 1/8 inch to ¼ inch in diameter. Mistletoe shoots form two to three years after infection. Look for mistletoe shoots, bunched growths of branches called “witches’ brooms” and branches with swellings.
The seeds shoot from the capsule at speeds up to 60 miles per hour and usually travel for horizontal distances of 10 to 15 feet, sometimes as far as 60 feet. They are sticky and adhere to any surface they strike. Seeds that adhere to young branches of susceptible trees germinate and the mistletoe rootlet penetrates the bark. Birds occasionally may spread the seeds to uninfected trees. Dwarf mistletoe seeds are generally dispersed in August and early September. The spreading of mistletoe is produced by small berry like seeds that break away from the stems of the mistletoe. Mistletoe spreads slowly from tree to tree. In closely spaced trees of about the same height this spread is 1 to 2 feet per year. Most dwarf mistletoe’s usually specific to a particular type of tree does not infect other tree species.
Dwarf mistletoe kills by slowly robbing the tree of both water and food. The tree slowly dies from the top down as the lower infected branches take more food and water. Mortality of infected trees does not occur rapidly in most cases and depends on the severity of infection, and the vigor and size of the tree. Infected trees can take many years to die. This allows for long-term disease management and the planting of species that are resistant to this species of dwarf mistletoe.
Control mistletoe by cutting down heavily infected trees and pruning lightly infected ones. Remove trees severely infected or those with only a few live branches. Trees with high, unreachable mistletoe infections will continue to shower seeds on nearby trees if not removed. It is not necessary to completely eradicate the mistletoe since it may require removal of all trees. Mistletoe shoots die quickly; therefore it is not necessary to burn or destroy the trees or cut branches. Do not stack the wood against living trees because insects could build up and attack living trees. Thin trees to help control mistletoe. Plant a resistant conifer that grows naturally in the area, such as Douglas-fir, white fir, blue spruce, pinon pine, limber pine, Rocky Mountain juniper, bristlecone pine and gambel oak. Select the species that are hardy in your area.
- For more information contact:
- C.S.U. Extension Service for Service in Action sheet 2.925
C.S.U. Extension, (719) 636-8926