Hydrilla, invasive aquatic vegetation that caused so much concern just a few years ago, is now virtually non-existent in Smith Mountain Lake. Sterile grass carp placed into the lake this past April have devoured every sign of the dreaded weed.

Hydrilla was first discovered in Smith Mountain Lake in 2007. The invasive aquatic vegetation has a history of growing out of control in several lakes and waterways. If left unchecked, the weed has been known to completely take over coves to a point that they can make any type of water recreation impossible.

What made the hydrilla such a concern is the fact that it is nearly impossible to get rid of once it enters a lake. If a part of the weed is split from the main plant, it can possibly regrow into a new hydrilla plant. Also, one square meter of hydrilla can produce 5,000 tubers and can remain dormant for several years in sediment.

The Tri-County Lakes Administrative Commission has spent hundreds of thousands of dollars over the years on herbicide to control the hydrilla. The herbicide, at best, prevented the hydrilla from growing further in the areas where the hydrilla was known to exist. In the areas where it had yet to be discovered, the hydrilla grew freely without the herbicide.

TLAC decided to add 6,000 sterile grass carp this past April as a more effective and cheaper way to combat the hydrilla problem. The sterile grass carp were known to have an appetite especially for hydrilla. And so far it seems that the carp have eliminated virtually all of the hydrilla in Smith Mountain Lake.

According to TLAC Project Coordinator Pam Collins, they have received no reports of hydrilla from lake residents this year. Divers have also searched many of the areas where there were once acres of hydrilla, such as an area around Crazy Horse Marina, and have found none.

“They are doing a fantastic job,” Collins said.

Since the carp are sterile, there numbers are slowly dwindling. About 10 percent of the 6,000 sterile grass carp are expected to die off in the first year, according to Collins. The carp have a total lifespan of around 10 years, but may need to be replenished before that time.

There are no current plans to add any more sterile grass carp in the near future, since there is little hydrilla left for them to eat. She doesn’t want to add more carp that could possibly eat some of the native aquatic vegetation that can be beneficial for the lake.

While eliminating hydrilla is nearly impossible, Collins is optimistic that the sterile grass carp could come close. Studies show that the hydrilla tubers can stay viable for 10 years. If the grass carp can prevent the tubers from growing for those 10 years, Collins is hopeful that the plant may disappear. Collins did stress that there is currently no study to prove that just yet, but she is hoping that Smith Mountain Lake could be the first instance.

“We wouldn’t mind being a pilot project toward that goal,” Collins said.

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