REPRODUCTION AND DEVELOPMENT OF THE BIOCONTROL AGENT HYDRELLIA-PAKISTANAE (DIPTERA, EPHYDRIDAE) ON MONOECIOUS HYDRILLA

Previous investigations of the laboratory biology and host range of Hy drellia pakistanae, a biological control of Hydrilla verticillata (hyd rilla), 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 investigat ed 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 substra tes. Overall developmental success differed little: 42% of eggs ovipos ited on monoecious hydrilla produced adults compared to 39% of eggs ov iposited on dioecious hydrilla. Fly development required about 33 days on both biotypes (at 22 +/- 2 degrees C), but larvae that completed d evelopment mined 1.6 times as many leaves on monoecious hydrilla as on dioecious plants. These data suggest that H. pakistanae would be a us eful biocontrol agent of monoecious hydrilla, should this plant invade areas where it can grow as a perennial. (C) 1996 Academic Press, Inc.