Photographer: Kim Camilli Affiliation: Texas Forest Service Source: Bugwood.org Copyright: (CC BY-NC 3.0)
The Japanese dodder (Cuscuta japonica) is a parasitic vine that requires a host plant for food and water to survive. It is normally an annual plant but it may overwinter on host plant and in warm climates it can grow year round. The smooth stems have many branches and lack chlorophyll so they can vary in appearance from pale green to gold. The vine appear leafless but actually has scale-like leaves along it. The plant attaches to its host with peg-like roots called haustoria, which penetrate the bark and extract everything needed for survival. As seen in the picture above, the stems can blanket the entire host plant. Inconspicuous pale-yellow flowers can appear and the fruit is a two-cell capsule containing four seeds. The seeds are tiny (less than .1inch) and a black to pale straw in color.
Host Plant: Since this plant is a holoparasite it requires a host plant to survive. IT can parasitize several species including: Live Oaks, Privets, Crape Myrtles, willows, Buckeyes and can potentially affect orchard trees, eggplants, potatoes, onions, pumpkins, tobacco and soybeans.
The threat of this plant is apparent because it is a parasitic vine and can kill its host in 2 to 3 years. As mention in the host plant section it is capable of destroying crops making it a serious threat to the horticultural and agricultural industries. It can also thrive in riparian zones, killing off native plants, which can severely alter the food chains and eliminates shade and nesting habitats. Although tall trees may be resistant to the Japanese dodder, the understory is more susceptible. Also, maintenance costs of both private and public landscapes would increase as infested plants are removed and replaced. Finally, the Japanese is host for several serious citrus viruses that can be transmitted to orchard crops.
The Japanese dodder reproduces by seeds (up to 2,000/plant) that can be carried over long distances by moving water, machinery or soil disturbances like erosion. Seeds can remain viable from 10 to 20 years but must usually germinate within a year. The seeds can germinate in the soil or on the bark of the host plant because the seedlings are rootless and leafless. The seedlings will die if they do not find a host plant; they are able to “sense” a potential host by spreading out the twine tips towards other plants. The Japanese dodder can also reproduce vegetatively by stem fragments, and those stems can grow inches in a day.
The Japanese dodder was accidentally introduced on kudzu plants in San Antonio, Texas; Quincy, Florida, and Clemson University campus in South Carolina. All vines were thought to be eradicated but it was rediscovered in Houston, Texas in 2001. In 2003-2004 a cooperative project with the City of Houston and the Texas Forest Service tried to eradicate the dodder. Also in 2004, it was found in Redding, California and by 2010 it was found in over 245 sites. Now any shipment found to contain whole dodder seeds of any species is denied entry into the United States. But in spite of precautions. Seeds are also intentionally imported and distributed as a medicinal herb, thankfully they are usually pulverized and are not viable.
Japan and Temperate eastern Asia, including Mongolia, China, Korea and Taiwan
U.S. Habitat: This holoparasite can attach itself to herbaceous or woody host plants in a variety of habitats ranging from riparian zones to crop fields or orchards.
Texas sightings reported by Citizen Scientists are listed here
U.S. Present: CA, FL, SC and TX
Dodder refers to more than 150 parasitic, yellow twining plants, so the Japanese dodder can resemble native dodder species. However, native dodder species usually parasitize herbaceous plants and small shrubs while the Japanese dodder can overtake trees in addition to plants and shrubs.
There are no known biological controls for this plant. Luckily, on small infestations cutting the infected host plant to the roots, then bagging all host and dodder fragments and disposing of them in a deep commercial landfill can help control the dodder infestation. Because of the risk of re-infection neither the host nor dodder should be composted. Widespread infestation can be managed by frequent, tilling, burning or herbicide applications. Pre-emergent herbicides will prevent germination of dodder seeds and kill seedlings that have no host. Post-emergent herbicides will kill both the dodder and the host; but allows plant debris to be removed without threat of fragments re-sprouting.
Jianzhong, H., & Yanghan, L. 1987. A Study of the Developmental Anatomy of Haustoria of Dodder (CUSCUTA JAPONICA CHOISY)[J]. Journal of Nanjing Agricultural University, 2, 000.
Westbrooks, R. G., & Eplee, R. E. 1996. Regulatory exclusion of harmful non-indigenous plants from the United States by USDA APHIS PPQ. Castanea, 305-312.
Westbrooks, R. G., Otteni, L., & Eplee, R. E. 1997. New strategies for weed prevention. In Conference Proceedings: Exotic Pests of Eastern Forests Nashville, TN TN Exotic Pest Plant Council and US Department of Agriculture.
Woodward, Susan L., and Joyce Ann. Quinn. 2011. Japanese Dodder. Encyclopedia of Invasive Species: From Africanized Honey Bees to Zebra Mussels. Santa Barbara, CA: Greenwood. 610-13. Print.