growing tip

heavy infestation, the rapid underwater growth "pushes" a portion of the mat above the water, giving the reservoir a field-like appearance

subsoil turions (tubers) at the end of horizontal stolons. These asexual reproductive structures are resistant to herbicides, and allow for rapid recolonization of a treated site

Joe Balciunas surveying for hydrilla agents (August 1983) at Lake Dal. Of the four agents approved for release two were shipped from India.

female Hydrellia pakistanae on leaf

Diagram of relative sizes of the abdomen in both the native Hydrellia spp. (right) and the introduced species (left)

Ventral views of the abdomens’ of both H. pakistanae and H. balciunasi showing the morphology of the external male genitalia. Note the cruciate or crossed macrochaetae in both species, a configuration that is not found in native Hydrellia species. The primary difference between the two introduced species is the size and shape of the macrochaetae. In H. pakistanae, the macrochaetae are smaller and needle-like in comparison to H. balciunasi where the macrochaetae are larger and spoon-shaped at the ends

The cerci, located at the posterior end of the abdomen, are used to identify female Hydrellia. In H. pakistanae the cerci are distinctly L-shaped in contrast to H. balciunasi where the cerci are roughly triangular.

The life stages and feeding damage

adult and larvae, and associated larval damage

Mean number of immatures per kg and % leaf damage at release and non-release sites during 1999 and 2000 for sites in Texas, Georgia, and Florida.