Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Hydrilla Stems and Tubers As Hosts for Three Bagous Species: Two Introduced Biological Control Agents (Bagous Hydrillae and B. Affinis) and One Native Species (B. Restrictus)

Authors
item Wheeler, Gregory
item Center, Ted

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2006
Publication Date: April 16, 2007
Citation: Wheeler, G.S., Center, T.D. 2007. Hydrilla stems and tubers as hosts for three Bagous species: two introduced biological control agents (Bagous hydrillae and B. affinis) and one native species (B. restrictus). Environmental Entomology. 36(2):409-415.

Interpretive Summary: The species Hydrilla verticillata is an invasive weed that threatens waterbodies throughout the southern US. We studied the biological control of this weed by two weevils, a hydrilla tuber weevil Bagous affinis and hydrilla stem weevil B. hydrillae imported from India and Australia, respectively. Additionally, a native species, B. restrictus was found feeding on hydrilla at biological control release sites. Larvae of the hydrilla stem weevil could feed and survive as well on tubers as on stems. However, the same could not be said of the tuber weevil as larvae of this species could complete development only on tubers. These findings indicated that feeding on tubers by the hydrilla stem weevil may benefit the species particularly when hydrilla stems are seasonably absent or unsuitable especially in more northern climates. In terms of hydrilla control, damage to tubers by this species constitutes a reduction in future infestations of hydrilla propagated by tubers. Finally, hydrilla is suitable to the native weevil, B. restrictus as larvae completed development in hydrilla stems.

Technical Abstract: Field observations suggested that the introduced Hydrilla verticillata (L.f.) Royle biological control agent, a stem weevil Bagous hydrillae O’Brien would feed on dioecious hydrilla tubers as well as stems and a native species, Bagous restrictus LeConte would feed on hydrilla stems. In choice tests the stem weevil B. hydrillae readily oviposited in hydrilla tubers. Larval development of this species B. hydrillae in hydrilla tubers was similar to that in stems; greater adult biomass was attained and less time was required to complete development when the larvae were fed tubers. Larvae of the hydrilla tuber weevil, B. affinis Hustache, did not complete development in hydrilla stems. Larvae of the hydrilla tuber weevil, B. affinis, completed development more rapidly when fed new- compared with old-hydrilla tubers. The native, B. restrictus successfully completed development in hydrilla stems, although the larvae required slightly more time compared with the biocontrol agent, the hydrilla stem weevil B. hydrillae. These findings indicated that feeding on tubers by the hydrilla stem weevil may benefit the species particularly when hydrilla stems are seasonably absent or unsuitable especially in more northern climates. In terms of hydrilla control, damage to tubers by this species constitutes a reduction in future infestations of hydrilla propagated by tubers. Finally, hydrilla is suitable to the native weevil, B. restrictus as larvae completed development in hydrilla stems.

Last Modified: 10/30/2014
Footer Content Back to Top of Page