Impact of foliage feeding by Zygina sp. on tuber biomass and reproduction of Asparagus asparagoides (L.): relevance to biological control in Australia

A form of the southern African plant Asparagus asparagoides (L.), is a severe environmental weed in Australia, where it is known as bridal creeper, and is the target of a biological control program. It has an extensive underground tuber system which complicates the use of mechanical and chemical control methods. Surveys in South Africa for potential biological control agents failed to identify any organisms that directly attack the tuber system of the plant, restricting selection to organisms that attack the aboveground parts for further consideration. One of the agents since released in Australia is a Zygina sp. (Hemiptera: Cicadellidae). The ability of Zygina sp. to impact negatively on the tuber mass of A. asparagoides, through indirect effects induced by extensive foliage damage, is demonstrated experimentally. A reduction in flowering and fruiting in response to attack by Zygina sp. is also demonstrated.