Host specificity testing of Hydrellia lagarosiphon for the biological control of Lagarosiphon major
Lagarosiphon major (Hydrocharitaceae) is on the EPPO List Invasive Alien Plants and an invasive alien species of (EU) Union concern. L. major is an aquatic plant originating from Southern Africa. It can colonize freshwater lakes, waterbodies, slow-moving streams, deep reservoirs, and dams where it forms dense monospecific populations which often colonise the entire water body, restrict water movement, cut off light, produce anoxic conditions and trap sediments. In Ireland, the estimated damage caused by aquatic invasive plants will rise to 3.8 billion EUR annually by 2030 if there is no successful management. Research into the classical biological control of L. major has identified a promising leaf-miner Hydrellia lagarosiphon (Diptera: Ephydridae). Host specificity testing was conducted against a predetermined list of plant species including four introduced and two native species in the family Hydrocharitaceae, plus 40 other species in seven families of Alismatales, all native to Ireland. No-choice and choice tests were conducted using neonate larvae and the results showed some non-target feeding damage on native Potamogeton species. Plant species which showed susceptibility in the tests were further tested in multigenerational population persistence tests where 1st instar larvae were reared through generations on these plant species. Three non-target plant species sustained development (though significantly reduced compared to the target plant) of H. lagarosiphon to adult though the population did not survive beyond the third generation for any of the non-target species.
Sources
Mangan R, Baars J (2023) Risk assessment of the host range of Hydrellia lagarosiphon for the biological control of Lagarosiphon major in Ireland. Biocontrol Science and Technology. https://doi.org/10.1080/09583157.2023.2215993