Guest columnist Brooke Thomas: Leverett Pond: Controlling invasives

  • Leverett Pond is shown earlier this year. FILE PHOTO

Thursday, March 03, 2022

It is with considerable reluctance that I enter into the “pond debate” where an adamant no-herbicide stance counters one of managing the spread of invasive “weeds” through the limited use of herbicides.

My better angels are warning it best to stay out of such heartfelt controversies since the resulting ruffled feathers can lead to long-term animosities and uncomfortable labeling; something we should avoid in this small town. Personally, engaging in this issue is complex — not black or white — since I am sympathetic to both sides.

As most Leverett residents, our collective gut reaction in using a chemical application to suppress invasive weed growth is problematical. After all we have been saturated by stories of Monsanto and Cargill’s abuses. Conversely, the idea of an invasive plant clogging the shorelines, out-competing native vegetation, and compromising recreational use of the pond is equally daunting.

The Friends of Leverett Pond (FLP) has been criticized for not considering alternative methods of control, and urged to consult with other ponds in the area for their advice. Below we hope to show that, indeed, we have tried most of these methods, and have sought the advice of other pond groups. Due to the extent of the pond’s area we have concluded that an approved and targeted herbicide would be most feasible and effective means of control. We are, however, hoping with the restored dam that a seasonal drawdown of the pond level could replace this method of control.

To begin, I suspect that most of FLP members would like to get away from the use of herbicides in checking the spread of milfoil and other invasives. But let’s go back 26 years and review the saga of how we have come to this point. In 1993 a pond resident noted a rapidly spreading aquatic plant and sent it to a state botanist. It was identified as the dreaded milfoil and subsequent testing revealed several variants.

The prognosis of what to do was not good as we learned it had taken over — engulfed — several ponds in the region. With the realization of the devastation this invasive could have on the pond’s ecology and recreational value, we joined the Massachusetts Coalition of Lakes and Ponds (COLAP), and worked with UMass WaterWatch in testing for dissolved oxygen, pH, water clarity, and sampling plant species composition in sections of the pond. While the pond seemed healthy, weed infested shallows had high temperatures and dissolved oxygen at levels too low to support most fish.

These organizations provided us with advice on an array of methods available, but given the size of the 102-acre pond, a state-approved herbicide solution was recommended as the only broad scale means to control weed spread into critical areas of the pond.

Nevertheless, the alternative methods were tried with the following results.

■Hand picking. Here it is necessary to pick the whole plant down to the roots in order to prevent fragmentation that would allow milfoil to float to other areas and colonize them. The mucky bottom on most of the shores makes this very difficult, however, once picking begins the water turns so cloudy that it is impossible to view and accurately pick more milfoil. Given the length of the shoreline this technique would be futile.

■Scuba divers. For reasons of water obscurity mentioned above this technique of milfoil picking is unfeasible. SCUBA only works once the plant mass is substantially reduced.

■Benthic bottom barriers. These are impermeable sheets spread across very small sections of bottom in shallow areas. They require continued maintenance because they accumulate gas underneath causing sections to float to the surface. They need to be removed every fall and would be unfeasible on a large scale.

■Insect predation. Milfoil consuming weevils were researched but it was determined that they would not consume the variety of milfoil in the pond. They are illegal in Massachusetts.

■Mechanical harvester (underwater lawnmower). Even though these cut and bail weeds they inevitably cause fragmentation and hence spread the milfoil.

■Hydro-raking. This machine scrapes up muck and rooted plants from the bottom and dumps them on shore. It is a cumbersome process of going back and forth one scoop at a time and hence can only go so far out.

■Herbicides. The advantage of this technique is that it can cover much larger areas than the above methods. In being absorbed rapidly into the root system it kills the milfoil without fragmentation, and, remains in free form in the water for only a few days.

The state has approved their use in its Generic Environmental Impact Report, and it has been permitted in the past by Leverett’s Conservation Commission. There are more studies that need to be done, but to date research has found no adverse effects. Over the years the FLP herbicide use has been applied to only 8% of the pond. And over time application procedures have improved the targeting of invasives and are absorbed more rapidly into the problem vegetation.

The herbicide used in 2019 (ProcellaCOR) has proven so effective in removing milfoil that there has been no application for the past two and a half years. Impacts to other plants are minimal or non-existent.

■Winter drawdown. Some ponds such as Lake Wyola use a drawdown to eliminate nuisance vegetation in shallow areas. Until the FLP restored the failing dam this option was not possible. However, with the new dam, water level can be gradually reduced. This would involve a 2-3 foot drawdown that would occur in November and December, slowly allowing shoreline fauna to migrate with the receding water and reach its prescribed level by the time of freezing temperatures. The dam gate would then be closed allowing the pond to refill by spring.

■Do nothing. A remaining option is to accept the invasive as a natural process that will hasten the eutrophication of the pond: “let the pond be a pond” or do nothing. This option over the span of a decade will considerably reduce open water and therefore its recreational value (swimming, boating, fishing, bird watching). Also, it will make access from shore, including public access, more difficult and compromise native fauna dependent on open water.

In essence the FLP has applied for a permit from the Leverett Conservation Commission hat attempts to keep the pond healthy for all and maintain its diverse habitats — that is, to keep the pond as we know it. And although vegetation will continue to encroach it is still the town’s most valued resource. On Jan. 31 the Concom approved the permit with conditions.

Brooke Thomas is a member of the Friends of Leverett Pond, and has lived near the pond and mucked around in it's lovely waters for 47 years.