In 2006 the Collins Pond Improvement Association began a project to reduce the infestation of hybrid variable leaf milfoil in Collins Pond. Eradication of this non-native plant has always been the long-term goal but reducing the heaviest infestations had become the most practical annual project. The majority of the cost of our long-term project has been covered by the Maine DEP Plant Control grant program. The remainder of the cost of the project has been supported by donations from our lake association members and several local businesses in addition to the Town of Windham Watershed Protection grant program.
To eradicate milfoil you must either remove the entire plant including the root ball or smother the plants using benthic mats. We started using the mats in 2006 expanding their use until we collected enough money to build our own DASH boat (Diver Assisted Suction Harvester). In 2010 we began using our DASH boat with our own trained, volunteer divers and crews. In 2014 we began annually hiring a local private contractor that specialized in removing invasive plants to supplement our own efforts. The cost of maintaining and insuring our own boat along with the gradual aging-out of our volunteer crews made it necessary to retire our own boat in 2022. Since 2010 we have harvested over 178,000 gallons of milfoil plants which have been composted on local farms. We continued to work with the staff at the Maine DEP Invasive Species Program to develop the most effective method to eradicate this invasive plant.
In 2023 the Maine DEP agreed to develop an herbicide treatment plan in order to get better control over this infestation. Collins Pond was a good candidate for this treatment due to its relatively small size and extensive areas of infestation. It was hoped that one treatment might control the plants but a follow-up treatment in 2024 was always a possibility. The diver survey performed at the end of the summer, 2023, showed that the treatment was very successful but that concentrations of plants still existed. The DEP suggested that one more treatment would be needed in 2024. As in 2023, we partnered with the DEP to send out notices to property abutters, posted notices around the lake where people would access the water and at the central cluster mailbox location.
The herbicide treatment was performed on August 14th by the licensed applicator and was overseen by the DEP staff. The DEP staff also performed water testing at that time and later to determine that the concentration of herbicide was correct on the day of treatment and also when it was no longer detectable. The herbicide chosen by the DEP, ProcellaCOR, was used because of its relative safety. It is fairly specific in its ability to kill the milfoil plants with little harm to most other native plants. There were no concerns about toxicity to fish or other wildlife in or on the lake at the concentration that was used.
A diver survey was performed on October 30th and no viable milfoil plants were seen, only rotted stems with no leaves in a few areas. The native plants looked healthy and there were no adverse effects on the fish and other lake wildlife.
We will plan on a week of DASH work next summer in case there is a regrowth of milfoil in some areas. Prior to the treatment this summer there was very limited regrowth noted except where plants during the post-treatment survey in 2023.
