The annual treatment of the lakes for Eurasian watermilfoil is set for Monday, May 14.
Lake Management Director Richard Grannells said residents should be aware that there is no swimming or watering of livestock in treated areas until May 15, no drinking or cooking with the water until May 18, and no irrigation with lake water until May 20.
“It will probably be too cold for swimming and people don’t normally use it for drinking or cooking, there’s no livestock right there, so irrigation is really the main thing people have to be aware of,” said Grannells.
Parts of Middle Pond and South Pond will be treated with a selectively targeted herbicide called Diquat. Aquatic Control Technology of Sutton will perform the work.
Grannells said Eurasian watermilfoil is a non-native invasive plant. It has feathery underwater foliage and was once commonly sold as an aquarium plant. Eurasian watermilfoil originates from Europe and Asia, but was introduced to North America many years ago and is now found over much of the United States.
Grannells said the plant is widely distributed and difficult to control.
“Twelve years ago we had to do a whole lake treatment,” Grannells said. “In successive years, we have done spot treatments and the area is less and less every year.”
The sheer mass of plants can cause flooding and the stagnant mats can create good habitat for mosquitoes. Milfoil mats can rob oxygen from the water by preventing the wind from mixing the oxygenated surface waters to deeper water. The dense mats of vegetation can also increase the sedimentation rate by trapping sediments.
Grannells said people couldn’t swim or boat in it.
“It grows so rapidly it can go unchecked,” he said. “It can grow from the bottom of the lake to the top surface and form a tent on the water. It can take over other good plants and kill fish.”
Grannells said Eurasian watermilfoil also generates its own fertilizer, which aids to its rapid growth. It can also grow from cuttings, so if a boat runs through it and cuts it, the leaves can start a new plant.
Aquatic Control Technologies was scheduled to be in Southwick Friday, mapping out the areas to be treated on a GPS. On Monday, the treatment crew will use the GPS to administer the Diquat.
