Biological control of nuisance algae and macrophytes is a rapidly devel-
oping area of lake and reservoir management.
A number of insects and plant
pathogens are operational and have been proven to be successful in control of
waterhyacinth and alligatorweed.
Restructuring of fish communities offers
great promise for algal control but may be impractical for large reservoirs.
The introduction of phytophagous fish (primarily sterile, triploid grass
carp) for control, or more likely elimination, of macrophytes has proven to be
Significant problems can be associated with their
successful and inexpensive.
Grass carp are operational in several states.
Table 15 is a summary of biological control techniques.
Summary of Biological Controls
Macrophytes and algae.
Modes of action
Grazing by fish, insects, and zooplankton.
Infection with pathogens.
Variable, dependent on biological control agent and
Short- to long-term.
Possible replacement of one noxious plant species by
Environmental conditions can control distribution
and effectiveness of control agents.
Potentially less expensive than typical mechanical
or chemical controls.
Questionable due to open nature of some reservoirs.