Results of Herbicide Treatment – One Year Later


In June of 2010 we treated the lake with the herbicide triclopyr.  Details of this expensive and politically difficult undertaking can be found elsewhere in this blog.  By the end of the summer we were enthusiastic about the success of our project.  Virtually all of the Eurasian Milfoil was lying dead on the bottom of the lake and decomposing.  The year-end report required by the State confirmed this observation.

This June aquatic biologists from Lycott performed a detailed examination of the lake.  Our program this summer would depend on how much milfoil they found.  It is possible that in the denser beds of milfoil some rootstock may not have had exposed stalks or leaves, and could have escaped the herbicide.  They did indeed find some milfoil, but an amount that can be easily managed this year with hand harvesting.

Our conclusion is that the herbicide treatment was a resounding success. Yes, there is still some milfoil in the lake, but it is substantially all gone. You can read the details of what they found below, but it is a minuscule fraction of the pervasive infestation of the entire littoral area of the lake in recent years.

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LYCOTT aquatic biologists have conducted three (3) surveys during June of 2011.  The first survey was conducted June 14th.  Its primary purpose was to track the effectiveness of the 2010 herbicide treatment.  In an email summarizing their work, the scientist wrote:

Click here for larger image

“E. Milfoil was found in one location during the littoral zone survey and in one of the three areas where Brittany dove.  As you can see from the map, the first location was at the Middle Brook inlet, relatively close to the State boat ramp.  There are plants scattered among the native species in this shallow area.  Attached is a photo of the heaviest growth we found – you can see a lot of Elodea in the background.

Brittany dove at three locations where growth was heavy in 2009 – near Passumpsic Point (?), the beach at Treasure Island, and the large patch that was close to the camp at Lochearn Rd.  As you can see from the map, the second location of growth was off of Passumpsic Point.  She picked everything in her field of view while swimming ~150 ft. and came up with about 5 plants.”

The second survey was conducted June 24th and 25th.  Two SCUBA divers swam the entire circumference of the lake.  their purpose was to direct the proposed 2011 hand-pulling operation.  After the first day the diver wrote:

“So far we’ve identified only three places with milfoil. Two are in Middlebrook Bay and the third is east of Aloha Hive, north of their swim area. Middlebrook Bay has at least one small, dense bed.. other sites are very sparse and fairly unhealthy looking plants.”

And after the second:

“Nothing much more to report. Found scattered plants in Middlebrook Bay along with one small, but dense patch of plants.”

The third visit was by Will Stevenson, the president of Lycott, accompanied by Sarah Miller, a representative of the herbicide’s manufacturer.  I met with them on the lake, and received the impression that they are very pleased by the success of the treatment.

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This Year’s Program

What does this mean for our milfoil program this year?  Here is our consultant’s recommendation:

“Based on the findings of the three June 2011 surveys, LYCOTT recommends deploying a 2-person dive crew to conduct two separate 2-day hand-pulling events to remove Eurasian Milfoil plants. The first event will be conducted in early July to focus on removal of identified plants in the Middle Brook inlet area and the area adjacent to the Aloha Hive Camp, north of the swim area. The second 2-day hand-pulling event will be scheduled for late August to re-survey the littoral area and hand-pull any late-summer growth that emerges.”

The LFA board will likely accept Lycott’s recommendation and hire them to perform the indicated hand pulling.  We also plan to continue our Courtesy Greeter program at the boat ramp. (more here)