MTP aquatic threat continues to make incursions downstream, DES scientist says

An airboat leaves Everetts Cove Marina as it prepares to apply herbicide in 2017 to combat the invasive weed European Naiad to an area of Northeast Pond. (Rochester Voice file photo)

MILTON - While several years of aggressive chemical and manual removal of the European Naiad have decreased overall density levels in Milton Three Ponds, the DES limnologist leading the fight against the invasive aquatic plant said it continues to make incursions downstream.

The infestation was first discovered on Northeast Pond in September 2015 and since then has been closely monitored by volunteers under the direction of York County Soil and Water Conservation District, the local interstate Three Ponds Protective Association, New Hampshire Department of Environmental Services (NH DES) and Maine DEP.

During the summer of 2017 portions of Northeast Pond were treated with an herbicide called diquat, which proved successful, however, state Invasive plant species coordinator Amy Smagula of DES said the pesky aquatic plant continues to spread misery farther east within the Milton Three Ponds system.

According to Smagula, diving and spot herbicide treatments have been performed to reduce the density and distribution of the plants and overall densities have decreased, but there has been "some continued spread from Northeast Pond to the downstream ponds (Milton and Townhouse), and those are also under management," Smagula told The Rochester Voice.

European naiad can overtake native lake habitats by shading and outcompeting ecologically valuable aquatic plants, European naiad grows from an annual seed into 7-foot long plants. A productive, one-acre infestation can generate tens of millions of seeds per season. Dense infestations can alter water chemistry and oxygen levels threatening both native fish and plants.

To help prevent the aquatic weed's spread boaters are required to wash their boats before putting them in at Milton Three Ponds boat ramps at Town Beach and Everetts Cove Marina in Lebanon, Maine.

Smagula said plans are currently under way for additional control activities this summer to help further reduce the Naiad's presence.