Exotic water primroses (Ludwigia spp.) are aggressive invaders in aquatic ecosystems worldwide. To date, management of exotic Ludwigia spp. has been limited to physical and chemical control methods. Biological control provides an alternative approach for the management of invasive Ludwigia spp. but little is known regarding the natural enemies of these exotic plants. Herein the biology and host range of Lysathia flavipes (Boheman), a herbivorous beetle associated with Ludwigia spp. in Argentina and Uruguay, was studied to determine its suitability as a biocontrol agent for multiple closely related target weeds in the USA. The beetle matures from egg to adult in 19.9 ± 1.4 days at 25 °C; females lived 86.3 ± 35.6 days and laid 1510.6 ± 543.4 eggs over their lifespans. No-choice development and oviposition tests were conducted using four Ludwigia species and seven native plant species. Lysathia flavipes showed little discrimination between plant species: larvae aggressively fed and completed development, and the resulting females (F1 generation) oviposited viable eggs on most plant species regardless of origin. These results indicate that L. flavipes is not sufficiently host-specific for further consideration as a biocontrol agent of exotic Ludwigia spp. in the USA and further testing is not warranted.

In the search for specific natural enemies to control two invasive aquatic plants (IAP) from South America, Ludwigia grandiflora subsp. hexapetala (Onagraceae) and Myriophyllum aquaticum (Haloragaceae), taxonomic challenges associated with two Lysathia Bechyné, 1959 (Chrysomelidae; Alticini) species had to be resolved. Lysathia flavipes (Boheman, 1859) exhibits significant morphological variation, causes heavy damage to both IAPs, and may represent more than one species due to the phylogenetic gap between hosts. Additionally, an undescribed Lysathia species (previously published as Lysathia sp.), sourced from Brazil, has been successfully used as a control agent for M. aquaticum in South Africa since 1994. An integrative taxonomic approach combining genetic and morphological analyses was employed. A lectotype and paralectotypes for Graptodera flavipes Boheman, 1859 are here designated. Phylogenetic studies revealed that L. flavipes had greater genetic and morphological variation than originally described, and no evidence suggested that L. flavipes represented a species complex associated with its host plants. As a result, the species description was expanded. On the other hand, genetic and morphological differences such as body size, colouration, and genital structures further supported the description of Lysathia cilliersae Cabrera, sp. nov. and its differentiation from other closely related species, including L. flavipes and L. ludoviciana (Fall, 1910). Specimens of L. cilliersaesp. nov. collected in Misiones, Argentina, matched those from South Africa. Genetic sequences correlated with morphological vouchers, images, and illustrations of morphology and genitalia, as well as new distribution records, are provided. This research contributes to the taxonomic knowledge of the Lysathia genus and supports accurate species identification in applied entomological contexts, such as biological control programmes.

Las plantas invasoras sudamericanas del género Ludwigia (Onagraceae) degradan muchos ecosistemas ribereños y acuáticos en todo el mun-do. El control biológico puede ayudar en el manejo de estas malas hierbas exóticas, pero los datos sobre la especificidad de hospedero de los enemigos naturales de Ludwigia son limitados. Se estudió la biología y el rango de hospederos de Sudauleutes bosqi Hustache (Coleoptera: Curculionidae), un herbívoro de Ludwigia spp. en América del Sur para determinar su sostenebilidad como agente de control biológico de 3 especies exóticas de Ludwigia spp. (objetivos) en los EE.UU. Los gorgojos mantenidos a 25 °C (± 1 °C) con un fotoperíodo de 14:10 h (L:D) se desarrollaron a lo largo de 7 estadios de vida, con un tiempo de generación de huevo a adulto de 17,6 (± 1,2) dias cuando se criaron en la maleza objetivo Ludwigia hexapetala (Hook. & Arn.) Zardini, Gu & PH Raven (Onagraceae). No hubo diferencia en la longitud corporal media entre las hembras (2,6 ± 0,1 mm) y los machos (2,5 ± 0,1 mm). Se realizaron pruebas de variedad de hospederos de opción múltiple y de elección múltiple utilizando 3 especies exóticas de Ludwigia spp. y 8 especies de plantas nativas de EE. UU. Las larvas de Sudauleutes bosqi completaron el desarrollo en las 3 malezas objetivo y las 4 especies de plantas nativas, y la oviposición sucedió en todas menos 1 de las especies de plantas que apoyaron el desarrollo de las larvas. En las pruebas de opción múltiple, S. bosqi ovipositó en 9 de las 11 especies de plantas analizadas. Los resultados indican que la selección de hospederos y el desarrollo de S. bosqi no se limita a las malas hierbas objetivo, sino que también incluyen valiosas especies no objetivo. Por lo tanto, S. bosqi no es lo suficientemente específico para el hospedero como para ser considerado como un agente de control biológico de especies exóticas de Ludwigia en los EE. UU. y no se garantizan pruebas adicionales.

In the search for insects as biological control agents for the water primrose, the delphacid Pissonotus paraguayensis (Delphacidae) was found on Ludwigia grandiflora subsp. hexapetala (Onagraceae) in a wetland of Central East Argentina. The morphology of the unknown females (brachypterous and macropterous) and immature stages are described and illustrated. Adults and nymphs were collected in wetlands of Del Plata River Basin, from Buenos Aires to the northeastern part of Argentina. A rearing methodology was developed to perform biological studies. Both winged forms and structural features of the female genitalia are described for the first time at the genus level. Eggs and immature stages are described and keyed; fifth nymphal instars may be easily recognised by the yellowish colouration, blackish on dorsal of head, thorax and abdomen with conspicuous yellowish pits, ventrally only darkened on base of frons extended to lower level of eyes and dorsal surface of antennomeres I and II, and legs with distinctive black marks at femoro-tibial joint and apex. The geographical distribution is updated, expanding its range into Argentina, making Buenos Aires the southernmost limit of the genus in America. Biological information of the species is also reported here: life cycle, fecundity, oviposition behaviour, and host plant. Field observations showed that P. paraguayensis breeds, feeds, and causes damage to L. g. subsp. hexapetala. This delphacid presents a certain degree of specificity to the Ludwigia species in the Jussiaea section in host specificity tests. More studies are required to test this species as a potential biological control agent.