Biology, distribution, and host range of Zygina sp (Hemiptera : Cicadellidae), a potential biological control agent for Asparagus asparagoides

Surveys in South Africa for potential biological control agents for Asparag us asparagoides, an environmental weed in Australia, revealed the presence of an undescribed leafhopper (Cicadellidae: Typhlocibinae: Zygina sp.). Thi s paper examines the biology, distribution, and host specificity of Zygina sp. to ascertain its potential as a control agent. Eggs are deposited benea th the epidermis of mature phylloclades and nymphs feed predominantly on th e underside of phylloclades. Zygina sp. has five nymphal instars which requ ire means of 37.5 +/- 0.5, 20.6 +/- 0.2, and 12.2 +/- 0.2 days to develop t o adults at 15, 20, and 30 degrees C, respectively. Nymphs and adults cause d extensive damage to phylloclades at these temperatures. Adults survive mo re than 150 days on A. asparagoides plants but less than 5 days if given on ly water. Natural enemies include strepsipterans, mites, and mymarid egg pa rasitoids. Host-specificity testing in the laboratory and data from field s urveys revealed that Zygina sp. feeds on closely related species, especiall y within the Asparagaceae, although eggs are laid on only a few species whi ch, with A. asparagoides, were previously included in the genus Myrsiphyllu m. Zygina sp. occurs throughout the range of its preferred hosts in South A frica, inhabiting winter-, even-, and summer-rainfall areas. The results in dicate that Zygina sp. has potential as a control agent for A. asparagoides in Australia. (C) 2000 Academic Press.