Solanum mauritianum Scopoli and Solanum sisymbriifolium Lamarck are major exotic weeds in South Africa, while Solanum viarum Dunal is similarly problematic in the United States of America. All three species are native to northeastern Argentina and southeastern Paraguay, where they were surveyed for natural enemies in February 1998. Insect agents for Solanum weeds have a tendency to extend their host ranges to include non-target Solanum species, in particular cultivated eggplant (S. melongena L.), during laboratory trials, making it difficult to promote their release. To facilitate the interpretation of such results, other native and cultivated Solanum species that grew in close proximity to the target species were also surveyed to give an indication of the insects’ field host ranges. During the survey period, 19 insect herbivore species were recorded on S. mauritianum, while 8 species were recorded on each of S. sisymbriifolium and S. viarum. Based on the insects’ occurrence, abundance and damage to their target weeds, and their absence on other non-target Solanum species, several natural enemies that warrant further investigation were identified. These include 5 species associated with S. mauritianum and 2 species associated with each of S. sisymbriifolium and S. viarum. With rare exceptions, these insects were normally associated with a single host species and none attacked cultivated eggplant.