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|Title:||Biological and host range studies with Bagous affinis, an Indian weevil that destroys hydrilla tubers|
|Authors:||United States. Agricultural Research Service.|
University of Florida. Department of Entomology and Nematology.
Aquatic Plant Control Research Program (U.S.)
Buckingham, Gary R.
Bennett, Christine A.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Hydrilla verticillata (L.f.) Royle (common name hydrilla) is a noxious aquatic plant introduced into the United States from Africa through the aquarium industry. Two reproductive structures that enable hydrilla to withstand extremely harsh weather conditions are turions or winter buds (dense clusters of apical leaves that are produced in the leaf axils, green and ovoid-conical shaped buds) and bubil-like hibernacular structures, commonly, but incorrectly, called tubers (formed at the ends of stolons buried in the substratum). Tubers can remain dormant in the sediment for several years and remain viable. Hydrilla plants may be found in lakes, rivers, drainage and irrigation canals, ponds, and streams. Severe infestations of hydrilla can restrict boat traffic and interfere with fisheries and waterflow. Hydrilla is a nuisance adventive submersed aquatic plant that reproduces by fragmentation, tubers (which may remain dormant in the substrate for several years and yet remain viable), turions, as well as by seeds (in the monoecious variety). This plant is one of the most prolific problem aquatic plants in the United States, causing problems in many lakes and reservoirs with recreation and navigation. It is extremely difficult to control because of its varied methods of reporduction. Hydrilla is found in many southern states, California, and recently Virginia; it is removed in most cases by mechanical methods or by using herbicides. Mechanical removal tends to increase the spread of hydrilla because of fragmentation; while herbicides are used in various places, a major concern exists for the environment and water quality. This report has been prepared to consolidate information on the biology and host range studies of Bagous affinis Hustache (a tuber feeder on hydrilla). The results from this study showed that although the mean length for females grown in cultures was significantly larger than field-collected females, significant differences did not exist between males. In adult feeding preference tests on hydrilla stems, leaves, stem turions and tubers, stems were preferred 4:1 by newly emerged adults, while older adults fed only on the stems. In host specificity studies, B. affinis did feed on a few other species, however, not to any great extent; therefore, it does not appear likely that this insect will cause any major problems with native species. Although drawdowns of lakes, canals, and reservoirs will eliminate the aboveground biomass of hydrilla, the tubers can withstand extensive periods of drought. Based on laboratory studies, it appears unlikely that Bagous affinis could be established in the field in the cold northern areas of the United States and probably not even northern Florida. Because of the lack of a seasonal dry period in most areas of the United States, establishment of field populations seems unlikely. However, the insects could be reared in southern Florida and transported to sites during the early summer to aid in tuber reduction.
|Appears in Collections:||Technical Report|