Management of cattail, pickerelweed, and other invasive aquatic plants
is part of the Florida Fish and Wildlife Conservation Commission’s (FFWCC)
Aquatic Habitat Enhancement Program for Lake Istokpoga.
Lack of adequate fluctuation, reversal of the natural fluctuation
cycle, and low water levels during the prime growing season for aquatic plants
have encouraged expansion of cattail, pickerelweed, and other invasive plants
in Lake Istokpoga since 1962. Bands
of dense cattail and pickerelweed encourage the development and expansion of
tussocks and tussock precursors (water primrose, burhead sedge, water
hyacinth, water lettuce, etc.) by reducing wind and water movement throughout
littoral areas. Lack of water
movement limits flushing of detritus on which tussocks may form.
Cattail, pickerelweed and other tussock precursors not only displace
more desirable aquatic vegetation communities, but also deposit organic debris
on the lake bottom. Loss of
native littoral plants and sandy benthic substrates reduces areas for fish
spawning, forage and juvenile fish habitat, waterfowl feeding, public access,
and navigation on Lake Istokpoga. Although
some animals exploit cattail and tussock precursors for nesting and protective
areas, the overall ecological and economic impacts to the lake are strongly
negative.
FFWCC’s Aquatic Habitat Enhancement Program is broken into three
components with the primary goal of the program being enhancement and
management of Istokpoga’s aquatic habitat for the long-term benefit of fish
and wildlife and the people who utilize those resources.
The three program components include:
a)
mechanical
removal or consolidation of tussock and associated organic sediments;
b)
establishment
of native aquatic plant species through natural recolonization or
revegetation with desirable native aquatic plant species;
c)
management of
future tussock formation through control of invasive aquatic plants with
herbicides and aquatic harvesting.
In Spring 2001, the FFWCC conducted an aquatic habitat enhancement
drawdown on Istokpoga, in which 1,308 acres over 21 miles of shoreline were
scraped of tussock and organic material.
These enhanced areas provide sandy substrate on which native desirable
plants are encouraged to grow. However,
pickerelweed, as the primary aquatic plant invader in these sites, becomes
dominant and creates monoculture stands, which begin to exclude other
desirable plants. Also, since
1998, the FFWCC has maintained a seasonal aquatic harvester program around Big
Island, Bumblebee Island, and Henderson’s Cove to control tussock expansion
and reestablish productive littoral habitat.
This program is limited, however, by water depths at the machinery can
effectively operate and high program costs (>$4,000 per acre).
An aquatic plant management program, which includes herbicide
management of invasive plants and revegetation with desirable native species,
is necessary to provide more diverse habitat, which is better utilized by fish
and wildlife.
Invasive aquatic plants are controlled with aquatic herbicides to
encourage recruitment of desirable plants and increase the diversity of
aquatic plants throughout the lake. Invasive
species targeted include, but are not limited to, dense pickerelweed, dense
cattail, burhead sedge, water primrose, water hyacinth, and water-lettuce.
A long-term maintenance program has been implemented in coordination
with the Highlands County Aquatic Weed Control Project and Florida Department
of Environmental Protection’s Bureau of Invasive Plant Management to
maintain desirable vegetation communities and prevent formation of tussocks.
As part of FFWCC’s aquatic plant management program, dense stands of
cattail, pickerelweed, and other tussock precursors are managed with
herbicides by helicopter or airboat (less than half of the cattail and
pickerelweed is actually treated within the treatment areas) to leave bands of
sparse cattail and pickerelweed, which are better utilized by fish and many
wildlife species. Areas of dense
vegetation are left available for use by waterfowl, wading birds, and other
wildlife as roosting and protective habitat. Bulrush (buggy-whips), knotgrass (Kissimmee grass), and other
desirable native vegetation will not be sprayed. The herbicides to be used are glyphosate (tradenames:
AQUANEAT or RODEO) and 2,4-D Amine (tradename = WEEDAR 64), which are the same
chemicals many homeowners use to treat weeds in their yards.
The Florida Fish and Wildlife Conservation Commission's Division of
Freshwater Fisheries has selected a total of 1,024 acres of dense vegetation
for herbicide treatment as part of the Lake Istokpoga Fish Management Area (FMA)
aquatic habitat enhancement program. Areas
to be treated by airboat range along the shoreline from Highlands Park Estates
to Istokpoga Canal. Areas
to be treated by helicopter include Big Island marsh, Bumblebee Island marsh,
and Grassy Island, areas within Henderson’s Cove, and south of Istokpoga
Canal. Depending on weather conditions, the airboat treatment is
scheduled to begin on October 6 (Monday) through October 30 (Thursday).
The helicopter treatment is scheduled to begin on October 27 (Monday)
and continue through October 30 (Thursday).
Maps showing treatment areas will be posted at Istokpoga's public boat
ramps and local fish camps. Please
try to avoid these areas during the spray operations.
For additional information, contact Beacham Furse or Larry Davis at
(863) 462-5190.