WSU Extension

Hortsense

Weeds : Dodder : Cuscuta spp.
(revision date: 6/9/2014)

Family: Cuscutaceae
Cycle: Annual
Plant Type: Parasitic

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

Biology
The parasitic flowering plant dodder (Cuscuta spp.) attacks living plants by entwining them in its slender stems. Dodder is characterized by its tangle of leafless, yellow to orange threadlike stems. The stems encircle host plants and steal nutrients and water from the host via modified roots called haustoria. Tiny white, pink, or yellowish flower clusters appear in June; seeds are produced from midsummer until frost kills the plant. Dodder seeds are gray to brown, irregularly round with a rough surface texture, and similar in density to the seeds of clover and alfalfa, which are favored host plants. Seed may be spread by irrigation water, in manure, or by physical transfer by humans or animals. Dodder seed can remain viable in the soil for 20 years. Dodder also spreads from plant to plant by its twining stems. Japanese dodder (C. japonica) can also spread vegetatively by broken portions of the stems carried by animals, humans, or machinery. In addition to weakening and reducing yield of infected host plants, dodder can transmit plant viruses including Beet Yellows and Cucumber Mosaic Viruses. SPECIAL INFORMATION: In WASHINGTON, smoothseed alfalfa dodder (C. approximata) is designated as a Class 'C' noxious weed. In OREGON, Japanese dodder (C. japonica) is a Class 'A' noxious weed and other non-native species of dodder (Cuscuta spp.) are designated as Class 'B' noxious weeds. These plants are also on the Oregon noxious weed quarantine list, which prohibits sale, purchase, and transport of plants, seeds, and plant parts except fruit intended for consumption. Management may be required by law in your county. Consult your local Noxious Weed Control Board for more information.
Habitat
Dodder is a pest of many broadleaf plants throughout much of North America. Crops such as alfalfa, clover, tomatoes, potatoes, onions, and safflower are particularly susceptible. Dodder is often found in fields where these crops are growing or have been grown in the past several years. Known weed hosts of dodder include common lambsquarters, pigweeds, Russian-thistle, and field bindweed. Dodder growth and development is favored by high temperatures and full sunlight. Japanese dodder is also a pest of ornamental shrubs and trees, including fruit trees.

Management Options

Non-Chemical Management
  • Pull and destroy dodder-infected plants before the parasite develops seed.
  • Cut or mow dodder-infected plants very close to the ground. Do not place infected plant materials in the compost.
  • Do not spread manure or hay with dodder in it.
  • Plant seed free of dodder.
  • In infested areas, replace known host plants with non-host species such as grasses, corn, or other monocots. Trees with bark (not seedlings) are also resistant to infection, but the foliage is vulnerable.
  • Maintain good general weed control to prevent dodder survival on other weed species.
  • Cultivate to kill dodder seedlings before they attach to the host plant.
  • Prune out infected portions of desired plants, cutting 1/8 to 1/4 inch below the lowest point of dodder attachment.
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: Dodder on fuchsia
Photo by: R.S. Byther