Introduction Hydrilla is
naturalized and
invasive in the
United States following release in the 1950s and 1960s from aquariums into waterways in
Florida, due to the
aquarium trade. It is now established in parts of southern Canada and in the United States from
Connecticut to
Texas, and also in
California. By the 1990s control and management were costing millions of dollars each year. The plant was introduced when a Florida West Coast aquarium dealer shipped live
Hydrilla from
Sri Lanka under the common name "Indian star-vine." These plants were considered unsatisfactory and were dumped into a canal near
Tampa Bay, where they flourished.
Hydrilla is frequently confused with
Elodea canadensis and
Egeria densa due to similar submerged growth form.
Problems in
Charles County.
Maryland. Due to the combination of herbicide resistance, high growth rates, high ecological adaptability, dispersion ability, and low resources required,
Hydrilla is able to invade almost every region of the world and spread at an alarming rate, affecting the ecosystem in a negative manner. The high photosynthesis rate of
Hydrilla leads to the depletion in dissolved carbon dioxide during daytime, which raises the pH, and to higher concentrations of oxygen. At night, the oxygen is used for
oxidative phosphorylation, resulting in anoxia, and carbon dioxide is replenished, which in turn lowers the pH. As an
invasive species in Florida,
Hydrilla has become the most serious aquatic weed problem for Florida and most of the U.S. Because it was such a threat as an invasive species, one of the first cost-effective broadscale herbicide controls developed was
fluridone. Unfortunately, this single-use herbicide resulted in fluridone-resistant
Hydrilla. "As
Hydrilla spread rapidly to lakes across the southern United States in the past, the expansion of resistant biotypes is likely to pose significant environmental challenges in the future."
Hydrilla populations have caused economic, environmental, and ecological damage.
Hydrilla can host a
biofilm of the
cyanobacteria Aetokthonos hydrillicola, which can produce the brominated
neurotoxin aetokthonotoxin — the causative agent of
avian vacuolar myelinopathy, a fatal brain wasting disease of waterfowl and raptors.
Management , Florida|150px
Hydrilla can be controlled by
herbicides, as well as
grass carp, itself an invasive species in North America. Insects used as
biological pest control for this plant include weevils of the genus
Bagous and the
Asian hydrilla leaf-mining fly (
Hydrellia pakistanae). In 2011 an inlet of
Cayuga Lake, one of the
Finger Lakes in New York State, faced a
Hydrilla introduction. The city of
Ithaca and other local officials used the chemical herbicide
endothall to try to head off establishment in the Finger Lakes, which would have been disastrous for their ecosystems. The first year nearly $100,000 and many man-hours were spent trying to eradicate the
Hydrilla infestation. Follow-up treatments were planned for at least five years. In August 2021
Hydrilla was discovered growing in a small boat marina connected to the Niagara River in the city of
North Tonawanda, New York. The New York State Department of Environmental Conservation is working to contain the infestation. In September 2021, the Connecticut River Conservancy stated that
Hydrilla has been overwhelming tributary rivers, coves, inlets and riverbanks along the river for years. Kelsey Wentling, a river steward at the Connecticut River Conservancy, stated, "
Hydrilla can spread through a process known as fragmentation, in which the plants, due to some sort of disruption, break apart and regrow elsewhere. Fragmentation often happens when boats go through a patch of
Hydrilla. For this reason, it is critical that those using paddle boats, power boats, jet skis, and fishing equipment in the Connecticut River be aware of invasive
Hydrilla and then take steps to reduce its spread." It has also been reported by local marinas and municipalities that they can no longer access certain boat slips and docks due to the density of
Hydrilla. The Connecticut River Conservancy in September 2021 requested area boaters to complete a survey to help with the ongoing management of the invasive plant. ==Phytoremediation==