Reproduction and development of the biocontrol agent Hydrellia pakistanae (Diptera: Ephydridae) on monoecious hydrilla

Previous investigations of the laboratory biology and host range of Hydrellia pakistanae, a biological control of Hydrilla verticillata (hydrilla), used the dioecious hydrilla biotype common to Florida, Texas, and California. A monoecious biotype that is now spreading throughout the mid-Atlantic states, California, and Washington was not investigated during these original studies. We therefore compared the dioecious and monoecious hydrilla biotypes as hosts for H. pakistanae. Female H. pakistanae accepted the two biotypes equally as ovipositional substrates. Overall developmental success differed little: 42% of eggs oviposited on monoecious hydrilla produced adults compared to 39% of eggs oviposited on dioecious hydrilla. Fly development required about 33 days on both biotypes (at 22 +/- 2 degrees C), but larvae that completed development mined 1.6 times as many leaves on monoecious hydrilla as on dioecious plants. These data suggest that H. pakistanae would be a useful biocontrol agent of monoecious hydrilla, should this plant invade areas where it can grow as a perennial. (C) 1996 Academic Press, Inc.