Identifying invasive weeds

Residents and visitors to Lake Wicwas are grateful that, at this time, no invasive weeds are present in the lake that we know of.  Lake Wicwas is most vulnerable to variable milfoil which is a prolific, exotic, invasive weed that inhabits many of the surrounding lakes.

To guard against variable milfoil arriving and taking root, the Lake Host™ Program is active during the busiest days at the local boat launching.   These Lake Host monitors inspect arriving boats to insure no variable milfoil or other weed of any type is traveling on the boat, motor or trailer.

Another activity to prevent an influx of variable milfoil is the Weed Watcher Program sponsored by the New Hampshire Department of Environmental Services. Several volunteers on Lake Wicwas take to kayaks about once a month during June, July, August and September to scour the shoreline in search of invasive, non-native weeds such as variable milfoil.

Milfoil vs. native weeds

Two common native weeds, which are prolific and often mistaken for variable milfoil, are bladderwort and elodea.  Although lay-person reports of possible milfoil sightings are encouraged and gratefully received by the Weed Watcher and Lake Host team members, the more accurate these reports are the less time is spent investigating mistaken sightings.

Below is a photograph showing variable milfoil, bladderwort and elodea side by side in water as they would be seen from a boat or kayak, followed by a detailed photograph of each of these three weeds.  (The milfoil was not retrieved from Lake Wicwas and was properly destroyed after this photo was taken.)  Click any of the pictures for a larger view.

Variable milfoil (exotic), bladderwort, elodea comparison

Variable milfoil (exotic), bladderwort, elodea comparison

Milfoil detail

Milfoil detail

Bladderwort detail

Bladderwort detail

Elodea detail

Elodea detail

Note the size of the foliage on the variable milfoil. It is considerably larger than that of the bladderwort and has each single strand emerging directly from the stem while the foliage of bladderwort is much more branched.  You may also be able to see the small bladders on the foliage of the bladderwort.  Elodea is noticeably different from either milfoil or bladderwort having more leaf-like foliage and smaller still than bladderwort. The size of these weeds can be estimated by using the grid pattern at the bottom of the tub of water in which they are floating – it is about 2 ½” square.

For more photos of these weeds and of other invasive plants see the New Hampshire Department of Environmental Services pictures of the “Frightful Fourteen” invasive species which pose risks to all lakes and ponds in New Hampshire. At the 2010 LWA Annual Meeting, Amy Smagula, Limnologist/Exotic Species Program Coordinator for the NH Department of Environmental Services, discussed Lake Wicwas and how to keep it healthy.  Amy asked us to be particularly alert to threats from three of the fourteen invasive species – variable milfoil, fanwort, and water chestnut. Click here to download a color PDF file of Amy’s slides.  Here are the pictures from pages 16 and 17 showing these three threats.

Chinese Mystery Snail

Chinese Mystery snail - top view

Chinese Mystery snail – top view

Chinese Mystery snail - bottom view

Chinese Mystery snail – bottom view

Although not a weed, another invader that is already in Lake Wicwas is the Chinese Mystery Snail.  These will be found near the shore and vary in size from ¼” to larger than 2”.  These snails  are in danger of driving the native fresh water mussels out by consuming the same food sources as the mussels need to survive. Snails found should be pulled well away from the water where they will likely be eaten by mink or muskrats.  The snail pictured here measured about 2 ½” from foot to tail and about 1 ¼” in diameter.

Reporting suspicious weeds

If you are boating on Lake Wicwas and see a weed which you suspect is invasive take a small sample, place it in a zip lock bag and deliver it to a Lake Host if one is on duty at the launch ramp.  If not, call the Lake Wicwas Weed Watcher coordinator at (603) 279-5242.  The person at this number will arrange to pick up your sample and, if suspicious, will deliver it to DES for expert examination.  The location where the weed was found is critical.  Note with as much detail as possible where you found it. Ideally mark it with a small anchor and float, such as an empty plastic bottle.

We hope to keep Lake Wicwas free of invasive weeds and other exotics such as snails and zebra mussels.  Your watchful eye can make the difference between success and failure.  Thank you for your interest.

Lake Wicwas Association
June 26, 2010
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