While treating Grant Lake in southwest Douglas County for flowering rush, authorities with the Department of Natural Resources confirmed the lake has zebra mussels.

On Thursday, Aug. 8, Grant Lake was treated for the aquatic evasive species flowering rush. Douglas County AIS prevention coordinator Justin Swart and the DNR's Mark Ranweiler accompanied workers from an aquatic plant and algae control company as they applied a herbicide to reduce the population of the flowering rush.

During the treatment, specialists from the county and DNR found multiple zebra mussels on a settlement sampler hanging on a dock. Settlement samplers are solid surfaces placed in the water so that people can regularly check for attached zebra mussels.

The flowering rush was discovered in mid-July by a retired DNR official. The DNR previously removed some of the flowering rush plants by hand, but treatment was still needed.

"We are fortunate that the officer spotted the flowering rush in its earliest stages," said Swart. "Treating it now should prevent it from spreading in Grant Lake and potentially to other lakes in the county."

Flowering rush, he said, looks similar to bulrush but it has a cluster of pink flowers on top. A submerged form of it does not produce flowers, however. Left untreated, Swart said the flowering rush can grow up to four feet and overtake natural habitat, crowd out native species and make it difficult for boats to access open water.

People should contact an area DNR aquatic invasive species specialist if they find an invasive species that has not already been confirmed in a lake.

To prevent the spread of invasive species, officials stress the importance for boaters to clean their watercraft when leaving a lake, drain all water by removing drain plugs and keeping them out during transport, and always disposing of unwanted bait in the trash.

This is the first documented case of flowering rush in Douglas County. Eurasian milfoil and zebra mussels are two aquatic invasive species that have been documented on other lakes in the county. Starry stonewort is also a concern.

On Saturday, Aug. 17, volunteers will be used to look for starry stonewort and other aquatic invasive species at public access points. Volunteers are still needed. The event, called Starry Trek, will begin at 8:30 a.m., and last until noon. A free lunch will be provided. People willing to volunteer are asked to register at www.starrytrek.org.

For more information about all of the lakes in Douglas County visit www.alexarealakes.org.