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U.S.-South African Cooperation Seeks to Tame Introduced WeedBy Kathryn Barry Stelljes
July 29, 1998
A new cooperative project between Agricultural Research Service and South African scientists aims to control Cape ivy, a weed rapidly taking over natural areas along the U.S. west coast.
The vine was introduced from South Africa as an ornamental plant before the turn of the century. But now it has spread into wild areas throughout coastal California and into Oregon, where there are no natural enemies to curb the weed's growth.
Cape ivy reduces the diversity of native plants and reduces precious habitat needed by rare and endangered plants and animals.
Chemical weed killer is frequently not a control option because Cape ivy grows in hard- to-reach areas, near water and in areas that contain sensitive species. So ARS' Plant Protection Unit in Albany, Calif. and South Africa's Plant Protection Research Institute in Pretoria are working to implement a biological control solution.
The Pretoria scientists began searching this spring along the east coast of South Africa for insects and pathogens that appear to control the ivy naturally. The researchers believe such biocontrols exist because Cape ivy is uncommon in its homeland, suggesting that natural enemies keep it in check.
Once potential biological agents are found, ARS will test them for safety on native U.S. plants. Ultimately, if an effective biocontrol is identified, ARS will apply for permission to release the insect or pathogen.
ARS has released hundreds of beneficial biological control agents against dozens of pests. The painstaking process of identifying, testing and importing a biological control insect takes about 10 years.