Submitted to: Biological Control of Invasive Plants in the United States
Publication Type: Book / Chapter
Publication Acceptance Date: December 1, 2003
Publication Date: September 1, 2004
Citation: Balciunas, J.K. 2004. Cape Ivy, Delairea odorata. In: Coombs, E.M., Clark, J.K., Piper, G.L., Cofrancesco, A.F., editors. Biological Control of Invasive Plants in the United States. Corvallis, OR: Oregon State University Press. p. 441. Interpretive Summary: Frequently, plants from overseas become naturalized in the USA, and some cause serious economic losses and environmental damage. One of these is the South African vine, Cape ivy, also known as German ivy. Although still widely sold as a houseplant, this vine is established in several states, but is most widespread and damaging in California. While it establishes most readily along streams and rivers, from there it readily invades into forests, shrub thickets, and grasslands. Usually, this vine forms a thick carpet that smothers and kills all other vegetation. It is considered to be poisonous to infants and pets that consume it. In this brief chapter, I summarize the problems this vine causes, and our current effort to develop biological controls for this invasive South African vine.
Technical Abstract: Cape ivy (Delairea odorata), also known as German ivy, is a native of South Africa that has become one of the most pervasive and damaging nonnative plants to invade coastal areas of the western United States. This vine has demonstrated its potential to cause serious environmental problems by overgrowing riparian and coastal vegetation, including endangered plant species, and is reputed to be poisonous to aquatic organisms. In California, Cape ivy is spreading in riparian forests, coastal scrubland, coastal bluff communities, and seasonal wetlands. Cape ivy was also introduced into the Big Island of Hawaii around 1909 and has become a serious weed in a variety of upland habitats there. Thus far, two insects have shown the most promise as safe and effective biological control agents in the United States. The host ranges of the gall fly Parafreutreta regalis and the stem-boring moth Digitivalva delaireae were extensively tested by USDA-ARS scientists in Albany, California, between 2001 and 2004. In addition, in South Africa, a flower-feeding phalacrid beetle, as well as a pathogen that damages Cape ivy leaves, show some promise as potential biological control agents, and may be tested.