Dye offered to block Lake Anna hydrilla

Lake Anna Civic Association volunteers apply herbicide in Freshwater Creek in 2018 to kill invasive hydrilla plants.

There is a new plan for fighting hydrilla in Lake Anna’s Freshwater Creek this summer, one that does not involve live carp or herbicides.

At its Jan. 22 meeting, the Lake Anna Advisory Committee agreed to try blue dye as a means to control the invasive plant.

In 2019, the creek was treated with herbicide in two applications. But the committee looked for alternatives after hearing some criticism from community members about the herbicide’s possible toxicity. Members also worried about the rising cost of herbicide application.  

John Cassel, the hydrilla subcommittee chairman, said the concentrated liquid dye can keep submerged hydrilla from growing by blocking sunlight. The dye would be added initially in June when many native species are already above the water level.

“Those plants wouldn’t be restricted in their growth cycle,” Cassel said.

How effective the dye is depends in part on how long it stays in the treated area, he said. If the dye stays put, the committee would treat the area three more times on a monthly basis for a total price of $1,100. Cassel said the dye is non-staining and poses no threat to humans or animals.  

In order to use the dye, the committee needs the approval of the Virginia Department of Game and Inland Fisheries and Dominion Energy.

Sarah Marshall, Dominion Energy representative, said the company is open to the idea but needs more details about the amount of dye and timing.

Cassel said the impacted area is about 24 acres in size, nine of them in what is referred as the flats, which becomes unnavigable in low water conditions, and 15 acres in the cove area. He said about 75 percent of the dye would be added to the cove with the remaining 25 percent in the flats area.

Cassel said he used the dye successfully to control unwanted grasses in ponds in a neighborhood he previously lived in.  

If the dye is not successful, the committee’s back-up plan is to revert to using herbicides. But the cost has increased dramatically. The committee’s contractor provided an estimate of $17,000 —$2,000 for travel expenses, $6,000 for the boat and time to apply the herbicide and $9,000 for the herbicide itself.  

State game and inland fisheries officials have told committee members that more herbicide would be needed than in the past to achieve the desired result, thus the higher cost.  

Robert Egan, a committee representative from Spotsylvania County, asked how residents in the impacted area would be notified prior to treatment.

Cassel said whether dye or herbicide is used, his plan is to contact homeowners’ associations in the area one month ahead of time. The associations would be asked to notify residents.

The committee approved spending up to $1,650 on four treatments using the blue dye, contingent on Dominion Energy’s approval.  

Cassel said no special permit or license is required to add the dye to the water and that volunteers can handle the work.

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