Biology of Immature Stages and Host Range Characteristics of Sudauleutes bosqi (Coleoptera: Curculionidae), a Candidate Biological Control Agent of Exotic Ludwigia spp. in the USA

Abstract

South American invasive plants in the genus Ludwigia (Onagraceae) degrade many riparian and aquatic ecosystems worldwide. Biological control may aid in the management of these exotic weeds, but data on the host specificity of Ludwigia natural enemies is limited. The biology and host range of Sudauleutes bosqi Hustache (Coleoptera: Curculionidae), an herbivore of Ludwigia spp. in South America, was studied to determine its suitability as a biological control agent for 3 exotic Ludwigia spp. (targets) in the US. Weevils maintained at 25 °C (± 1 °C) and a 14:10 h (L:D) photoperiod developed through 7 life stages, with a generation time from egg to adult of 17.6 (± 1.2) d when reared on the target weed Ludwigia hexapetala (Hook. & Arn.) Zardini, Gu & P. H. Raven (Onagraceae). There was no difference in mean body length between females (2.6 ± 0.1 mm) and males (2.5 ± 0.1 mm). No-choice and multiple-choice host range tests were conducted using 3 exotic Ludwigia spp. and 8 native US plant species. Sudauleutes bosqi larvae completed development on the 3 target weeds and 4 native plant species, and oviposition occurred on all but 1 of the plant species that supported larval development. In multiple-choice tests, S. bosqi oviposited on 9 of 11 plant species tested. Results indicate that host selection and development of S. bosqi is not limited to target weeds but also includes valued non-target species. Therefore, S. bosqi is not sufficiently host-specific for further consideration as a biological control agent of exotic Ludwigia spp. in the US and additional testing is not warranted.