WSU Extension

Hortsense

Weeds : Dwarf mistletoes : Arceuthobium spp.
(revision date: 6/9/2014)

Family: Loranthaceae
Cycle: Perennial
Plant Type: Parasitic

Use Integrated Pest Management (IPM) for successful weed management.

Biology
Dwarf mistletoe is a parasitic plant that grows on the branches or occasionally on the trunk of a host tree. Mistletoe shoots range in color from yellowish to olive-green to reddish depending on species. Shoot size is also variable, ranging from 1/4 inch to 8 inches long. The host tree's branches become swollen and spindle-shaped at the infection site, and may develop witches' brooms (loose fans to tight clumps of small twigs and foliage). Severe infestations can greatly reduce growth of the tree, sometimes causing dieback or death. However, since dwarf mistletoe survival depends on the survival of the host plant, death of entire trees is uncommon. Dwarf mistletoe spreads by sticky seeds that are shot forcibly away from the parent plant. In parts of Oregon, true or leafy mistletoes (Phoradendron spp.) also occur. Host plant symptoms and mistletoe appearance are somewhat similar to dwarf mistletoes; however, some true mistletoes have oval leaves 1 to 1 1/2 inches long. Seeds of true mistletoes are not forcibly ejected, but are typically spread by birds feeding on the berries.
Habitat
Dwarf mistletoe hosts include conifers such as Douglas-fir, true firs, larch, hemlock, pines, and junipers. In Oregon, true mistletoes may be found on junipers, firs, and hardwoods such as oaks and maples. Most mistletoes are fairly host-specific and will not infect species other than their host plant or its close relatives.

Management Options

Non-Chemical Management
  • Remove mistletoe from host tree by pruning out witches' brooms or hand-picking the parasite.
  • Plant non-host species in areas where mistletoe is a problem.
Select non-chemical management options as your first choice!

Chemical Management

No chemical controls are recommended for homeowner use.

Images
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Caption: Dwarf mistletoe
Photo by: R.S. Byther