First isolation of a Helicosporidium sp. (Chlorophyta: Trebouxiophyceae) from the biological control agent Cyrtobagous salviniae (Coleoptera: Curculionidae)

Cyrtobagous salviniae (Coleoptera: Curculionidae) is a weevil that has been introduced into at least 16 countries as a biological control agent for the floating fern, Salvinia molesta. Screening in Florida of C. salviniae imported from South Africa found a pathogen identified as a previously unknown species of Helicosporidium (Chlorophyta: Trebouxiophyceae). Fresh cysts measured 5.1 × 4.8 μm and ultrastructural examination demonstrated the presence of three ovoid cells surrounded by a filamentous cell. Cysts of this pathogen were isolated and transmitted to the alternate hosts Helicoverpa zea and Anopheles quadrimaculatus. This is the first report of a pathogen from C. salviniae and demonstrates the need for and value of screening and monitoring biological control agents for pathogens prior to introduction. Releasing healthy C. salviniae not only enhances the chances for successful control of S. molesta but also reduces the risk for the inadvertent introduction of pathogens that may have undesirable and unexpected impacts on native fauna.