Gratiana lutescens (Boheman) (Coleoptera : Chrysomelidae : Cassidinae) reconsidered as a natural enemy of satansbos, Solanum elaeagnifolium Cavanilles (Solanaceae), in South Africa

Solanum elaeagnifolium Cavanilles is a weed in low-rainfall agricultural ar eas of South Africa and is a target for biological control. The leaf-feedin g tortoise beetle, Gratiana lutescens (Boheman), was first considered as a biological control agent for S. elaeagnifolium in the early 1970s, but was rejected because it developed on eggplant and an indigenous Solanum species during larval no-choice tests on cut leaves. This insect was re-imported i n the late 1980s and larval no-choice tests were carried out on potted plan ts. The results were compared to those of cut leaves and indicated that the insect could be reconsidered for introduction. Gratiana lutescens was re-i mported from Argentina in 1995 for the present study and host specificity w as determined using larval no-choice tests on whole plants, and less conser vative paired- and multi-choice tests using adults. Gratiana lutescens was able to develop on a wide range of Solanum species. Although adult choice t ests indicated a narrower and possibly more realistic host range, the poten tial of this insect to oviposit and develop on indigenous Solanum species a nd eggplant indicates that it is not suitable for release as a natural enem y for S. elaeagnifolium in South Africa.