http://www.sun-sentinel.com/news/local/florida/orl-lochydrilla12061205jun12,0,4556641.story?coll=sfla-news-florida
June 12, 2005
Orlando Sentinel (Florida)
Hydrilla outsmarts herbicide, threatens
Florida's lakes anew
By Daphne Sashin
Sentinel Staff Writer
KISSIMMEE -- Hydrilla, the stringy weed that clogs canals and
chokes boat propellers, may be on the verge of an outbreak not
seen in Central Florida since 1999.
Scientists have found their best treatment
is losing its effectiveness because the fast-spreading weeds
are becoming tolerant to the chemical in lakes where it's used
most. In addition, they've noticed that micro-organisms
in the water are breaking down the chemical before it can start
working.
"It's a huge issue . . . because hydrilla is such a uniquely
adaptable plant. It can just overwhelm Florida waters in almost
no time," said Mike Bodle, a senior environmental scientist
with the South Florida Water Management District, which oversees
regional hydrilla control.
Tolerance to the aquatic herbicide fluridone
has been observed in Lake Istokpoga in Highlands County, several
lakes in Polk County and on Lake Seminole at the Florida-Georgia
border.
But the most serious problem is in the
Kissimmee Chain of Lakes, a 64,500-acre system that forms
the headwaters to the Everglades and where the state concentrated
more than half of its hydrilla-control budget this year.
It's where infestations have been the most severe and fluridone
has been used the most heavily, researchers say.
"It makes one sick, just to look out onto the Lake and
see the SEWER it is becoming," Lake Tohopekaliga resident
Robert Yuskaitis complained in a May e-mail to environmental
officials. "Does anyone have an answer?"
Scientists do not expect an effective replacement for fluridone,
which is sold under the trade name Sonar, for at least two years.
After continuing to up the doses, the water-management district
is reluctant to further increase the concentration of fluridone
for fear of the cost to taxpayers, the risk to other plants
and the increasing possibility it might not even work.
Hydrilla was introduced into Florida waters from Asia in the
late 1950s, and by the '90s had sprouted in nearly 140,000 acres
of water across the state. Half the state's hydrilla is in the
Kissimmee Chain of Lakes -- lakes Toho, Cypress, Hatchineha
and Kissimmee -- which the state calls its highest priority
because the system is part of federal navigation and flood-control
projects, according to a January report from the Florida Department
of Environmental Protection's Bureau of Invasive Plant Management.
Environmental officials principally relied on fluridone to
kill hydrilla because it was the only chemical that, when it
worked, attacked large sections of weeds at low doses, acted
slowly over several months and did not harm fish or other plants.
Last year, $8.32 million of the $8.63 million budgeted for hydrilla
control on the Kissimmee chain was spent on fluridone.
Florida scientists first got a hint that
the weeds were building tolerance to fluridone in 1999.
By that summer, hydrilla was strangling three lakes in the Kissimmee
chain so badly that boats couldn't pass through in several places.
The DEP was deluged with complaints from anglers, boaters and
waterfront homeowners who were fed up with the algae-covered
mats.
Biologists have managed to keep hydrilla
in check since then with higher concentrations of fluridone,
but they've seen an increased resistance to the herbicide. On
top of that, in the past two years they've noticed that certain
naturally occurring micro-organisms in lakes have learned to
use the herbicide as a source of food. Normally, scientists
view this as a good way to clean lakes of contaminants, but
in this case it's working against what officials are trying
to accomplish with hydrilla control.
Water managers finally curtailed the
treatment this spring when it failed to kill the weeds despite
a double dose.
"Unfortunately, these expensive treatments were performed
with little or no effect and cut off," Bodle said. "These
are probably the last fluridone treatments for the Kissimmee
chain."
Meanwhile, more than half that water system is infested with
hydrilla tubers, the DEP says. When they sprout from the soil
in a year or two, they may be untreatable and spread from the
Kissimmee chain to other waterways, said Mike Netherland, a
research biologist at the University of Florida's Center for
Aquatic and Invasive Plants.
"It's very likely to spread from that site to other sites
as boats go through the lake," Netherland said. "Having
30,000 acres of resistant plants almost guarantees that they're
going to spread pretty rapidly. That's one of the justifications
that we've used to say we really do need to manage on the Kissimmee
chain."
Officials at Se-PRO Corp., the Indiana company that markets
Sonar, think it is still a valuable tool if used appropriately,
said Steve Cockreham, the company's head of research and development.
When used repeatedly and at higher rates over time, the probability
of tolerance increases, he said.
"It's become a lot more complex in how you appropriately
manage the hydrilla in those particular lakes," Cockreham
said. "We haven't seen it anywhere else in the U.S. where
Sonar has been used."
Se-PRO is experimenting with a new herbicide that it expects
the U.S. Environmental Protection Agency and the state to approve
for widespread use in 2007. The new chemical has the same risk
for tolerance as fluridone, though, so environmental agencies
would put severe restrictions on its use, said Bill Graf of
the South Florida Water Management District.
The district will work to keep the waterways open for boats
with another chemical, endothall, which works well on small
sections but is difficult to apply and costs too much to use
lakewide, Bodle said. Endothall also carries a warning that
fish caught in the treated area within three days after an application
should not be eaten.
Agencies have found success in smaller lakes with weed-eating
grass carp, but they don't dare put them into the Kissimmee
chain for fear the voracious fish will eat all the other plants
in the lakes and then move on to other waterways.
Yuskaitis, 82, who has been called the "hydrilla guerrilla,"
complains that the open, beautiful water behind his house is
already overrun with algae and weeds.
"It bothers me because I know the consequences. You won't
be able to go out fishing anymore," said Yuskaitis, who
served on the Osceola County Lakes Management Advisory Board.
"It's so tenacious and so dense and thick, if you fall
in, it will twist you up and you won't get out of it."
Daphne Sashin can be reached at 407-931-5944 or dsashin@orlandosentinel.com
Copyright © 2005, Orlando Sentinel
