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ARS Home » Southeast Area » Fort Lauderdale, Florida » Invasive Plant Research Laboratory » Research » Publications at this Location » Publication #70348
Title: ATTEMPTS TO ESTABLISH HYDRELLIA BALCIUNASI (DIPTERA:EPHYDRIDAE) FOR THE BIOLOGICAL CONTROL OF THE SUBMERSED AQUATIC PLANT HYDRILLA VERTICILLATA (HYDROCHARITACEAE) IN TEXAS AND FLORIDA

Author
item GRODOWITZ, MICHAEL - US ARMY CORPS ENGINEERS
item Center, Ted
item COFRANCESCO, A - US ARMY CORPS ENGINEERS
item FREEDMAN, JAN - US ARMY CORPS ENGINEERS

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Hydrilla, a submersed aquatic weed that originated in the Old World, is a major obstacle to the safe and efficient use of water resources in many areas of the United States. Despite expenditures of millions of dollars annually in attempts to control this plant with aquatic herbicides, no permanently effective control method exists. Aquatic resource managers fear that they might be forced to use plant-eating fish, which eat a wide variety of aquatic plants (including desirable species), if no other techniques become available. Therefore, we are trying to find host- specific insects that eat this plant in it's native habitats and then importing them, after extensive testing, to the US for use as biological control agents. One of these is a small fly named Hydrellia balciunasi which is from Australia and has been demonstrated to feed and develop only on hydrilla. After an intensive effort we have finally succeeded in establishing this species at two sites in Texas. It is too early to determine its impact on hydrilla, but the established populations seem tenuous. If this agent is effective, it will save public agencies millions of dollars per year and help the preserve biodiversity and natural integrity of many of our native aquatic ecosystems.

Technical Abstract: The Australian leaf-mining fly, Hydrellia balciunasi Bock, was first released as a biological control agent for the management of the submersed aquatic plant, Hydrilla verticillata (L.f.) Royle on 1 Aug. 1989 at the Orangebrook Golf Course in Hollywood, Florida. Since that time more than 250,000 individual H. balciunasi have been released at 7 Florida and 4 Texas sites. Despite this intensive effort, populations have been successfully established at only two Texas sites, Sheldon Reservoir near Houston and Lake Raven in Huntsville State Park. Although populations have persisted at Sheldon Reservoir since September 1992, numbers have remained low averaging only 359 immatures per kg wet weight for June through October, the active growing season. Adults were readily captured with capture rates averaging 2 and 3 adults per hour for males and females, respectively. Reasons for such low establishment are unknown but are probably related to a complex of abiotic and biotic factors including competition with other introduced leaf-mining species, parasitism by native wasps, climatic differences, physiological changes in hydrilla, and possible poor viability of released individuals. More research is needed in order to understand the reasons for such low establishment success.