Variable Milfoil

Variable milfoil is creating a serious economic and recreational nuisance in New Hampshire lakes. Variable milfoil was first introduced in New Hampshire lakes in the late 1960s by way of discarded aquarium plants into lakes and other waterbodies. It then spread from lake to lake by boats, motors, trailers, fishing gear, and by natural forces.  Variable milfoil can live out of the water for hours and then rejuvenate once it is introduced to water again.

Because variable milfoil has no natural predators, it can grow at explosive rates, rapidly inhabiting shoreline areas. Small fragments of variable milfoil carried by water currents and waves created by boat traffic float in the water and form roots, allowing the plant to take hold in shallow waters and colonize another area of the lake. One small fragment of variable milfoil can potentially multiply into 250 million new plants within a year’s time. It can grow one inch per day to reach 18 feet in length, creating a matlike canopy near the water’s surface.  At this time, Monomonac Lake has approximately 30 acres that have been colonized by variable milfoil. The number of colonized areas can grow exponentially if left untreated.

Left untreated, variable milfoil will clog lakes, causing boating and swimming hazards and crowd out native species of aquatic plants, necessary for the food and shelter of fish and fowl. In extreme cases, milfoil has been implicated in the drowning of swimmers who became entangled in the long vine-like plants.

Less obvious is the increased nutrient loading caused by decaying organic matter, reduced dissolved oxygen levels, and increased levels of phosphorus and nitrogen which contribute to the rapid aging (eutrophication) of the lake and loss of property values.  Studies indicate that shoreline property values may decline as much as 20% to 40% when variable milfoil is present in the waterbody.

These results present important implications for prevention and control strategies.  Once introduced and fully established, variable milfoil is virtually impossible to eradicate. The use of herbicides is the best method available for treating the ongoing infestation at Monomonac Lake but it is very expensive. This year we are treating 30 acres at the cost of $11,490. NH-DES will contribute with a grant for 25% ($2,873). Our final cost will be $8,617 which comes from MLPOA member dues paid by lake property owners like yourself. Please help us protect the property and the recreational values of our homes by paying your membership dues.

by Lourdes Gray

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