Asparagus weeds in Australia - a South African perspective with emphasis on biological control prospects

Carien A. KleinjanA,B and Penny B. EdwardsA,C

A CSIRO Biological Control Unit, Zoology Department, University of Cape Town, Private Bag, Rondesbosch, 7701, South Africa.

B Current address: Zoology Department, University of Cape Town, Private Bag, Rondebosch, 7701, South Africa.

C Current address: PO Box 865, Maleny, Queensland 4552, Australia.


Summary

The results of an extensive South African survey to identify potential biological control agents for Asparagus asparagoides are discussed. Two forms of A. asparagoides were found that are distinguished by characteristics of the tuber system. Not all the natural enemies found in association with A. asparagoides attacked both forms. Three biocontrol agents (Zygina sp., Crioceris sp. and Puccinia myrsiphylli)from South Africa, have been released in Australia against the first form which has a wide distribution in South Africa. No candidate was found that damages the tuber system of this form of A. asparagoides, but foliage damage reduced tuber mass and fruit production under experimental conditions. The seed wasp Eurytoma sp. occurs throughout the distributional range of this form of A. asparagoides. Damage levels vary but can be 90% or more. The second form of A. asparagoides has only recently been found in Australia. In South Africa it is restricted to the winter rainfall region of the Western Cape. This form of the plant is a host for Zygina sp. and Eurytoma sp. and the tubers are damaged by weevil larvae, but Crioceris sp. and P. myrsiphylli were not recorded.
Potential taxonomic difficulties of some of the other Asparagus spp. that occur in Australia are discussed, and preliminary observations are provided on their associated natural enemies in South Africa.

Keywords: Asparagus, Asparagus asparagoides,Australia, biological control, Crioceris, environmental weed, Eurytoma, natural enemies, Puccinia, South Africa, Zygina.

 

Plant Protection Quarterly (2006) 21 (2) 63-68.