Crossville Chronicle, Crossville, TN

September 25, 2013

Exotic weeds invade Glade lakes

By Jane Walker
Sun contributor

CROSSVILLE — Exotic, invasive weeds are plants that are native to other parts of the world and have very aggressive growth habits. Needless to say, these plants are very undesirable. At this time, there are two exotic, invasive plants that are known to have been introduced into Glade lakes.

In 2007, it was discovered that a plant called hydrilla had become established in Lake Canterbury and Lake St. George. Hydrilla is an Asian plant that was brought to this country as an aquarium plant and escaped (or was released) into the wild. It quickly became a significant problem in lakes and waterways all over the country. Hydrilla can grow to the surface in water as deep as 20 feet and mat over on the water's surface, causing the lake to be virtually unusable. This plant spreads rapidly and is readily moved from one body of water to another by boats, water fowl and other means. In 2012, hydrilla was found in Lake Glastowbury near the boat launch which may indicate how the plant ended up in that lake. Over time, this plant will likely be relocated to most or all of our lakes.

The second exotic, invasive plant in the Glade lakes is curly-leaf pondweed. It is present in Lake Sherwood in problematic amounts and is also in Lake St. George. This plant has an unusual life cycle in that it begins growing in November and continues to grow all winter while other plants are dormant and the grass carp are inactive. In the spring and early summer, the curly-leaf pondweed completes its life cycle and dies back by the first of July. It is likely that next year this weed will move down stream from Sherwood to Lake Glastowbury and at some point will be pumped from Glastowbury to Lake Oxford.

Once a plant like hydrilla or curly-leaf pondweed invades a lake, there is no way to eliminate it. The best that can be hoped for is to reach a state of peaceful coexistence. The best tool to hold the hydrilla or curly-leaf pondweed in check in our lakes is the Asian grass carp. When present in the correct number, the grass carp will keep these plants grazed down so that they are not an impediment to the use of the lake. That has been the situation with hydrilla on Lake Canterbury. On St. George an unfortunate set of circumstances resulted in the hydrilla becoming a problem to lake use. Now, several years later, the carp population has been built up to the point that the hydrilla is finally being suppressed. The best way to protect our lakes from these plants is to build and maintain a healthy and appropriate grass carp population in each lake so that when the plants arrive a stable carp population is already established. This is the goal of the incremental carp stocking program being conducted by the Community Club.

It would be easy to conclude from the information above that the correct course of action would be to simply pour grass carp into all of our lakes and any potential plant problems will be avoided. As with most situations, the easy answer is not the correct answer. We know this to be the case because we have tried this approach. If too few carp are in the lake they will not be able to suppress the problem plants. But if too many carp are stocked in the lakes they will not only consume the plants but they will damage the habitat resulting in damage to the sport fishery. This very situation has occurred in Glade lakes in the past, resulting in the need for expensive restocking efforts by the Community Club. A careful and well-planned carp stocking program is called for, so that the plants are kept controlled but the lake habitat is not damaged. Residents and guests can help manage these plants by not moving the plants from lake to lake on boats, trailers or tow vehicles. These plants are now a part of our lakes and will not be going away. Lakes are complex ecosystems that are difficult to manage so that they can afford all the varied uses that our residents enjoy.