Plan for Keeping Lake Chocorua Free of Milfoil


Variable-leaf Milfoil -- leaves are arranged like a feather - INVASIVE

By Toby Page

If the CLA-CLCF does little or nothing to protect the lake from milfoil, it is only a matter of time before the lake is infested with milfoil (unless we are very lucky).

(1) As late as 1960 exotic aquatic plant species were unknown in NH lakes. By 1965 there was one NH lake infected with exotic milfoil. Now, as of 2009, there are 68 NH lakes infected with exotic milfoil. A marina on Lake Ossipee already is now infested, just 8 miles away from the boat launching areas on Lake Chocorua.

(2) There is some risk from kayaks and canoes, but the larger risks are boat trailers and the occasional motor boat that gets on the lake.

(3) A two to three inch-long fragment of healthy stem material of milfoil is enough to start a new colony.

(4) Because milfoil can grow 12 feet tall, and the Chocorua Lake is shallow, an infection could spread to most of the lake, including swimming areas.

How to Reduce the Risk for Lake Chocorua

(1) Limit the boat launch areas to just one, at the Grove. There has been good progress in limiting launch areas, but more needs to be done. Signs discouraging any launching anywhere but the Grove, may help. Signs explaining the risk of milfoil, may help. Getting a town ordinance prohibiting any launch except for the one at the Grove may help. Signs showing the how to identify milfoil may help (would it invite vandalism?)

(2) If we are successful in getting launchings only at the Grove, it makes sense to have inspectors and Lake Hosts at the Grove. Blair Folts has used Lake Hosts. The Hosts are partially subsidized by the federal government (I think), and don’t have to be local residents. The inspectors do not have be present all day every day. Having inspectors during peak times would reduce the risk. Paying the Patrol to increase his/her presence at the Grove would help. A sign at the Grove, explaining the risk would help. A sign for boat owners could explain how they can do their own inspection when none of the CLA-CLCF, Lake Hosts or Weed Watchers are not present.  A mailbox like container for disposal of weeds found in these inspections would help, which of course would have to be emptied.

(3) If a milfoil fragment gets into the lake and starts a colony, we have a year, possibly two years, to find it and eliminate it. Once the infection spreads it becomes impossible to eradicate. In other lakes, about 7% of discoveries of milfoil are found by lakeside owners. More discoveries of milfoil are found by swimmers and boaters. But the largest findings are by monitors looking for new colonies. In other lakes monitors use motor boats in their searches. We of course have to use canoes and rowboats (I haven’t tried kayaks, since it seems to me that it is hard to control the kayak and search with a viewscope at the same time.)


Bladderwort -- Leaves are in a repeated branching process

The monitors do not have go be on call for every sunny, calm morning. In fact if a monitor monitored just one or two mornings in a summer, this would be a significant help. If there were 6-9 monitors, that might be sufficient, especially if some monitors spent three mornings monitoring in the summer. (A morning is likely to be 2 hours on the lake.) The whole lake does not need to be monitored. From the shoreline to a depth of about 6-8 feet is sufficient, as I remember Amy Smagula’s advice two years ago. Not all the monitors have to monitor in the same morning, in a group. Two people can do a lot in a canoe or rowboat by themselves in 2 hours. Amy recommends that the lake shoreline be sectioned off and one or a few monitors be responsible for a section. The trick is to make the search path efficient – not going over the same spot and not missing spots. Amy has advice about how to monitor efficiently.

It seems to me that it may be harder to make efficient paths in canoes and rowboats, than it is in motor boats, which have wakes that help mark the tracks. On the other hand we have a small lake, and quite a few barren areas that can be quickly monitored.

Mac Lloyd has converted a rowboat to have a plexi-glass bottom. In testing it out Jim Bowditch and I found the plexi-glass bottom improved visibility, especially when a cape is used to put the viewer in the dark, with light coming from the water. David Farley and I explored around the lake. Sam Page used scuba equipment to see clearly the matted density of weeds at the north end of the lake.

(4) I strongly recommend learning from Amy Smagula and Blair Folts. Both have a great deal of knowledge in preventing, discovering, and eradicating milfoil.

(5) I also believe that awareness is a key factor of a successful program. Anyone can learn how to tell milfoil from bladderwort. When there is an aware community it is more likely to do something about the milfoil threat.