Mistletoe (Phoradendron spp., Viscum album)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- Phoradendron spp. are found in parts of the Eastern, Western, and Southern United States. Viscum album, common in Europe, is not a problem on poplars in the United States. Severely infected trees are weakened, predisposing them to insect attacks and to environmental stresses. Branch and trunk swellings caused by mistletoe reduce wood quality and serve as points of entry for stain and decay fungi.

Look For: Individual, or clumps of green flowering plants with white to pink berries in the fall. Branch or trunk swellings.

Mistletoe plant

Biology- Mistletoes are parasitic plants that depend partially on their host for support, water, and mineral nutrients. Male and female flowers are borne on separate plants. The parasite is spread by birds that eat the berries and then excrete the seeds. The sticky seeds adhere to branches, where they germinate. A penetration structure forces its way through the bark where the root system of the plant then develops within the branch. While the root system slowly spreads outward from the point of infection, the aerial portion of the plant develops. Several years are required from the time of infection until a seed bearing plant if mature.

Monitoring- Mistletoe is most easily detected in the fall and winter after leaves are off the trees.

Control: Mistletoe will not be a problem on poplars grown on short rotations, so no control is needed. Removing the aerial portion of mistletoe does not eliminate the problem because the parasite can survive within the host tissues and eventually produce new shoots. However, removing that portion reduces stress on the tree and also makes fewer seeds available for additional infections. Remove infected branches to eliminate the root system of the mistletoe. For Additional Information: Scharpf, Robert F.; Hawksworth, Frank G. 1974. Mistletoe on hardwoods in the United States. For. Pest Leafl. 147. Washington, DC: U.S. Department of Agriculture, Forest Service. 7 p.

Clumps of mistletoe plants.