Chemical spraying controls invasive aquatic plants on Lake Okeechobee

OKEECHOBEE — The Florida Fish and Wildlife Conservation Commission is in a war with invasive plants that threaten to take over waterways, crowding out native plants, fish and other aquatic life.

At a meeting held Feb. 8 at the South Florida Water Management District office in Okeechobee, Mariah McInnis, regional biologist with the Florida Fish and Wildlife Conservation Commission, said the aquatic plant spraying program is often the topic of controversy. The Feb. 8 meeting was the third such public meeting hosted by FWC to allow the public to comment on the aquatic plant spraying program. Ms. McInnis reviewed some of the questions commonly asked.

“Why are we targeting these plants?

“We target a plethora of species on Lake Okeechobee, mostly water lettuce and water hyacinth,” she explained

These plants are not native to Florida and they pose a significant threat to native plants, fish, wildlife. The invasive plants, which will spread across waterways in thick mats if left unchecked, can also hinder flood control.

“They create mats that block out sunlight and reduce oxygen in the water,” she said. The floating mats can become entangled with native vegetation and uproot the native vegetation.

The invasives grow quickly all year round, she explained, and they float so they are constantly moving around.

Ms. McInnis said she creates the spraying plan based on weekly airboat surveys and monthly helicopter flights.

“We hear ‘applicators are spraying everywhere they are killing everything.’

“Our applicators use a variety of herbicides that are each used in different situations,” she said. The work is assessed post-treatment and FWC check for damage to non-target plants.
She said three companies which have contracts to spray aquatic vegetation on Lake Okeechobee each have an assigned zone of the lake, and they follow the FWC plan to target invasive vegetation.

Another question often asked, she continued, is” “why don’t we utilize mechanical harvesting?”
She explained that machines that harvest aquatic vegetation pull up everything in their path, including native plants, fish and other aquatic life.

Mechanical harvesters are very slow, and must frequently return to shore to dump the harvested material, which must then be loaded on trucks to take to a dump site.

The process is expensive, costing $10,000 to $20,000 per acre. (Lake Okeechobee’s surface is 730 square miles or 467,200 acres.) On Lake Okeechobee, wind actions tends to push the floating mats of invasive plants into the native vegetation, which would make it difficult to harvest the invasives without pulling up the native plants, she said.

People often complain that spraying herbicides on the aquatic plants makes them fall to the lake bottom, which adds to the muck build up, Ms. McInnis continued.

“There’s no denying that when we spray the plant, it will go to the lake bottom,” she said. However, she added. “The amount that goes to the bottom after herbicide application is far less than if plants are not controlled.”

She said fishermen have complained about the loss of submerged vegetation.

“We agree that there has been loss of submerged vegetation. We believe this is in part due to high water levels that have deprived the plants of sunlight,” she said.

“Turbulent conditions also cause additional damage.”

She said some boaters claim that hydrilla has been sprayed.

“We don’t treat hydrilla on Lake Okeechobee unless it is blocking navigation,” she said. The last time hydrilla was chemically treated was in 2016 in Pearce Canal, she said.

Another common complaint is: “contractors are not managed and do whatever they want.”

“Work is assigned weekly,” she said. “They are required to check in with me daily. They also send me their GPS track to me on a weekly basis. Their work is assessed after treatment. My surveys are available online.

“All our applicators have to be licensed by Florida Department of Consumer Services and also have to have an aquatic certification,” she said. They have to attend training to keep their certifications current.

“They are paid hourly, not by the amount that they spray,” she said.

She said there are a variety of non-native invasive aquatic plants in Lake Okeechobee.

“If you see a contractor spraying and you don’t see water lettuce or water hyacinth, he may be spraying one of these plants as well,” she said.

Another common question is “can you stop spraying during spawning and hunting season?” she continued.

“For next year, for peak spawning and hunting seasons, our plan is to clean up these areas really well before the season and limit spraying during season,” Ms. McInnis said.
During the public comments portion of the meeting, Jeff Seeger said there have been areas of overspraying, and that is something that does need to be taken care of.

“I have a lot of people who can take you to areas where there has been indiscriminate spraying,” he said.

Ms. McInnis said the public can report any problem areas to FWC.

“I’m a bass fisherman,” said Dave Walker, who said he has lived in the area for 18 years.

“I understand the ups and downs of bass fishing,” he said.

“Two years ago there was so much hydrilla by the pier you could almost walk on it,” he said. “Now it’s gone.”

“I am concerned about some of the areas back in the cattails,” he continued. “The water is clear when you get back out of the main body of the lake. These little pockets of reed grass are all dying. I don’t hardly see any green on that reed grass at all. I think they are spraying it. I think the spraying has to go on but I think they need to be careful on how or where they spray.”

“We know we have to have low lake stages in order to burn Lake Okeechobee,” said Gary Ritter of Florida Farm Bureau. “That’s probably the better ecological practice.”

“How do we go about cleaning the water before it gets to Lake Okeechobee?” asked Mike Krause of Okeechobee Fishing Headquarters. He asked about the possibility of using deep water injection wells to store excess water.

“Not a whole lot of water can pass underneath Alligator Alley,” he said. “Water has to move some place. It can’t move right now. Are deep water injection wells a possibility?”
Mr. Krause also suggested that Stormwater Treatment Areas (STAs) north of the lake could help slow the flow into the lake.

“Are there more places where STAs could be created north of here?” he asked.

“Fisheating Creek is a gorgeous place to fish,” he continued. “We talk about runoff water. That is runoff water, it comes for miles, but it’s clean water. It has to be filtering somewhere.”

Nyla Pipes, of One Florida Foundation, said there isn’t one county in the 16-county ecosystem that doesn’t have an issue with water quality and/or quantity.

She encouraged the public to get involved. She said the public can attend the Water Resources Advisory Commission meetings in person or view them online.

“It’s going to take every single one of us,” she said. “Every single Floridian has got to be involved in this conversation.”

Joseph Richter of Sebastian asked if they have looked at other ways of dealing with invasive plants other than mechanical harvesting and chemical spraying.
He said the high phosphorus and nitrogen levels in the lake water encourage the growth of non-native plants.

“Maybe addressing this upstream before it gets to the lake would allow the lake a break from all of the influx of nutrients,” he said.

“The fishing and hunting industry supports this area,” he said.

“Maybe they should think about expanding their horizon in limiting nutrients coming into the lake so there is less of an issue with the lake itself,” he said.

Larry Wise said spraying during the spawning season hurts the fisheries.

“On the east side of Little Grassy on Dec 18, I had caught a couple bedding bass along the shore,” he said. Then the spray crew came through that area.

“After the spray crew was done, I doubt very much a bedding bass would go back to that area,” he added.

“As a fisherman, I would like to see spraying stopped altogether in December, January and February. I think we are knocking down a lot of spawning type areas for bass and crappie.

It’s too bad we can’t do something mechanical to get the vegetation that needs to be moved,” he continued.

“I know we have to spray in the summer time,” he said. “In the spawning time, we can do without it.”

Publisher/Editor Katrina Elsken can be reached at kelsken@newszap.com

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