MAINTENANCE CONTROL

This is a supplementary part of the Herbicidal Control page of this web site.

MAIN INDEX | Suwannee River example | Lake Okeechobee example | Prevention |

BECAUSE IT IS IMPOSSIBLE to eradicate every single invader plant, "maintenance control" has become the mantra of Florida's invasive plant manager. Though it might sometimes appear to citizens that invasive plant control is unnecessarily frequent, there are good environmental and economic reasons for such frequency: the bottom line is, maintenance control reduces invasive plant numbers, reduces herbicide usage and reduces management and environmental costs.

Simply stated, maintenance control means managers must work continuously to keep the invasive plants down to the lowest levels possible.

The FWC's stated goals for maintenance control are to:

Minimize environmental damage caused by invasive plants

Conserve the uses and functions of Florida public waters

Enhance conditions for diverse and native plant growth

Use less herbicide in plant management

Lower management costs

Adapt management according to current conditions in each waterbody

Integrate plant management methods

Let the public know what to expect

Maintenance control is the "working philosophy" for aquatic and wetland plant management in Florida. Go here for a DEP statement about and further elaboration of these goals.

Studies at the University of Florida have shown that the amount of herbicide and effort used to manage aquatic plants at maintenance control levels is much less than the amount of herbicides and effort used to manage aquatic plants after they've become an obvious infestation. In a maintenance control program, even though more herbicide applications take place, the overall amount of herbicide used is much lower than the amount that would be used to treat an out-of-control infestation. Maintenance control also results in much reduced sediment deposition.

In Florida, frequent herbicide applications under the state's maintenance control program results in about 15,000 - 25,000 acres of floating plants being treated with herbicides each year, but with less than 5,000 acres being infested at any one time, compared to previous un-maintained conditions when as many as 125,000 acres of Florida's public waters were covered with floating plants.

The Suwannee River Example

The graph at the right shows the course of 34 years of water hyacinth management on the Suwannee River. (Click on the chart for a larger version.)

As can be seen, in 1974 the Suwannee River had about 2,300 acres of these floating plants. In places, boat traffic came to a standstill. Around 1985, after much use of the herbicide, 2,4-D, water hyacinth was finally placed under "maintenance control". Today, managers treat perhaps 200 total acres of water hyacinth on the Suwannee River during the course of a year. That's 92% less than the 1974 level!!

Now, native plants have returned to the shores and marshes of the Suwannee River, restoring fish and wildlife habitat.

"Acres controlled" since 1982 are the total acres of the small infestations of water hyacinth that continue to crop up, and be treated with 2,4-D in the maintenance control program. One can see that small infestations are continually found and treated every year.

Herbicide usage plummeted as the weeds came under maintenance control, although some herbicide continues to be applied as small infestations are discovered during the course of a year.

"Organics", meaning dead plant matter (produced mostly by live plants shedding leaf, root and shoot material) that would otherwise sink to create deep mucky sediment on the river bottom, were reduced by more than 95% under the Suwannee River maintenance control program.

This is an aerial photo of bulrush (a native plant) being pulled up by a shifting mat of invasive water hyacinth on Lake Okeechobee.

The Lake Okeechobee Example

While some floating plants can be removed mechanically and biological control agents are effective at reducing seed production and plant vigor in Florida, herbicide applications remain the most effective method for gaining and keeping maintenance control. This notion was confirmed in 1986 when a herbicide moratorium on Lake Okeechobee, FL, resulted in an expansion of water hyacinth from 2,000 acres to 8,000 acres in 5 months, despite continued harvester and biological control activity. In the final analysis, it took more than two years, $2 million and required controlling 11,000 acres of water hyacinth to regain maintenance control of water hyacinth in Lake Okeechobee.

This aerial photo (at right) tells a story: The “rust” brown areas depict invasive water hyacinth plants that were sprayed, in the initial phase of regaining maintenance control in early 1987 on Lake Okeechobee. In July 1986 a moratorium was placed on the use of herbicides on the lake. Notice how the remaining water hyacinths (i.e., the green plants) are choking off native cattail and bulrush.  The vast area of water hyacinth infestation was too much for mechanical harvesters and biological control methods. Without the use of herbicides, the plants quadrupled their coverage in just five months.

PREVENTION

Preventing the introduction and spread of non-native plants in Florida's waterways is the most effective and least expensive means of restoring Florida's natural freshwater habitats.

Like all plant management techniques, maintenance control is a costly but necessary tool to use in the fight to combat the invasive, non-native aquatic plant populations that are infesting Florida's lakes, rivers and wetlands.

Time and money spent on managing invasive species can be saved in the first place by preventing the introduction and spread of invasive species in the state's waterways. Public cooperation is an essential part of restoring Florida's natural habitats.

Please read here about steps you can take to help prevent invasive aquatic plant problems.