Submitted to: Biological Control of Weeds in the Eastern United States
Publication Type: Book / Chapter
Publication Acceptance Date: 10/1/2003
Publication Date: 3/1/2004
Citation: BALCIUNAS, J.K., GRODOWITZ, M.J., COFRANCESCO, A.F., SHEARER, J.F. HYDRILLA. BIOLOGICAL CONTROL OF WEEDS IN THE EASTERN UNITED STATES. 2004. p. 91-114. Interpretive Summary: Numerous non-indigenous plants have become established in the United States, and some have become serious weeds. Aquatic systems are also invaded by exotic weeds, and probably the most widespread and damaging in the U.S.A. is hydrilla (Hydrilla verticillata). Hydrilla is a submersed plant that once established, frequently not only displaces native vegetation, but fills the entire water body, from bottom to top, thereby greatly altering species composition, ecosystem function, and limiting recreational use, irrigation and flood control. In this chapter we review the problems caused by hydrilla, along with its distribution, origin and establishment in the U.S. Most of the chapter is devoted to cataloging the efforts to develop both insects and pathogens, as possible biological controls for this widespread pest. We elaborate on the four insects which have been approved for release in the United States, and review their establishment and impact. The information presented in this chapter shoul assist aquatic resource managers in choosing the appropriate approaches to controlling hydrilla. We also note research areas that would benefit from further investigation.
Technical Abstract: Hydrilla (Hydrilla verticillata) is a submersed plant that has become one of the most widesprread and damaging aquatic weeds in the United States. Once established, it frequently not only displaces native vegetation, but fills the entire water body, from bottom to top, thereby greatly altering species composition, ecosystem function, and limiting recreational use, irrigation and flood control. We review the negative impacts of this weed, along with its distribution, taxonomy, and origin. Hydrilla has been a target for biological control since 1971, and we tabulate the worldwide efforts to find potential biological control agents to use against this weed, and list nearly 20 organisms that have been considered as possible agents. Four overseas insects have been approved for release against hydrilla in the United States, and we reveiw the outcome of efforts to establish these four insects. Two insects (Hydrellia pakistanae and H. balciunasi) have become established in the U.S., and we review the studies to determine the impact these insects are having on hydrilla populations.