Host Range Studies with Bagous affinis (Coleoptera: Curculionidae), an Indian Weevil that Feeds on Hydrilla Tubers

Abstract

The plant host feeding range of Bagous affinis Hustache was studied in a Florida quarantine facility as part of a program for the biological control of hydrilla, Hydrilla verticillata (L. fil.) Royle, an immigrant submersed aquatic weed. Larvae attack hydrilla tubers in soil exposed during droughts or drawdowns. Thirty-nine plant species in 20 families were tested with larvae, and feeding was observed on 6 species. A few adults emerged from 3 species of Potamogeton and from Vallisneria americana Michaux. Adult feeding tests were conducted with 52 plant species in 29 families. Adults fed moderately on several species in 3 families: Apiaceae, the hydrilla family Hydrocharitaceae, and Potamogetonaceae. They fed heavily in no-choice tests on stems of the immigrant submersed weed Egeria densa Planchon, a close relative of hydrilla. Newly emerged females developed small numbers of eggs on 3 species of Hydrocharitaceae. Only 1 species, V. americana , could be a potential host plant, but the low oogenesis combined with low larval development indicated that it would be difficult for B. affinis to colonize this species in the field. In its native range in India and Pakistan, B. affinis has been reported only from hydrilla. Based upon a review of these data, USDA–APHIS issued a PPQ 526 permit on 17 February 1987 for field release of this biological control agent. B. affinis was subsequently released in Florida and California, but there are no reports of permanent establishment.