Biology
Bagous affinis is very small weevil ranging from
2.8 to 4.4 mm in length. Most B. affinis are black
and grey with evident scales.
This weevil is lays eggs on rotting wood and other organic
matter. Larvae hatch and burrow through the sediment until
they encounter a hydrilla tuber. Larvae complete their life
cycle while feeding on the hydrilla tuber and destroy the
tuber in the process. The major drawback of this weevil in
biological control is that it requires receding waters to
grow well. Thus, situations where the shoreline is intermittently
flooded or lake drawdown is practiced is required for the
weevil to develop. This has made it a very difficult species
to establish in many areas of the United States where hydrilla
is found primarily in lakes.
History
This weevil, was discovered in Pakistan and India while investigations
were underway for the biological control of hydrilla. In 1987
the U.S. Army Corps of Engineers released Bagous affinis
in southern Florida (Buckingham 1988). A summary of the releases
and recoveries in Florida is found in Center et al. (1991).
The weevil was first released in Texas in 1993 at the Sheldon
Reservoir in Harris county.
Weeds Affected
- Bagous affinis is known to feed only on Hydrilla.
Literature
Buckingham, G. R. 1988. Reunion in Florida – Hydrilla,
a weevil, and a fly. Aquatics 10(1): 19-25, illus.
Center, T. D., F. A. Dray, Jr., and W. C. Durden. 1991.
Release and Establishment of Insect Biocontrol Agents for
Hydrilla Control. Waterways Experiment Station, MP A-91-3.
O’Brien, C., and H. R. Pajni. 1989. Two Indian Bagous
Weevils (Coleoptera, Curculionidae), Tuber Feeders of Hydrilla
verticillata (Hydrocharitaceae), One a Potential Biocontrol
Agent in Florida. Florida Entomologist 72(3): 462-469.
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