Suitability of Using Introduced Hydrellia spp. for Management of Monoecious Hydrilla verticillata (L.f.) Royle

摘要

The main objective of this study was to determine the suitability of using introduced hydrilla leaf-mining flies (Hydrellia pakistanae Deonier and H. balciunasi Bock) for the management of monoecious hydrilla (Hydrilla verticillata (L.f.) Royle). This was accomplished using a variety of procedures and experimental designs, including small container bioassays, development of a greenhouse-based fly colony reared exclusively on monoecious hydrilla, a larger tank study designed to evaluate short-term impact on both monoecious and dioecious hydrilla, use of small ponds to evaluate establishment in a more natural situation, evaluation of overwintering biology of the agents, and field releases to determine establishment success. Introduction of biological control agents is a critical component of aquatic plant management. Using host-specific agents complements the goal of targeting nuisance vegetation while minimally affecting native vegetation. Two species of introduced ephydrid leaf-mining flies, Hydrellia pakistanae Deonier and H. balciunasi Bock, have been shown to suppress dioecious hydrilla by reducing photosynthesis, thereby impacting biomass production, tuber formation, fragment viability, and hydrilla's ability to compete effectively with beneficial native vegetation (Doyle et al. 2002, 2005; Grodowitz et al. 2003; Owens et al. 2006, 2008). However, only limited research has been conducted evaluating their effectiveness on monoecious hydrilla found in the more northern portions of the United States. Dray and Center (1996) indicated that the flies would be highly suitable, but this research was confined mainly to short-term laboratory and greenhouse-based studies with no actual field releases; hence, more research is warranted.