Eurasian Watermilfoil Myriophyllum spicatum

Tangled underwater stems and vast canopy of strings of paired leaves at the surface

  • English Name: Eurasian Watermilfoil
  • Latin Name: Myriophyllum spicatum
  • Propogate: Vegetative fragmentation and Seeds
  • Symptoms: Thick vast canopy of strings of paired leaves at the surface. Complete take over of a shallow lake
  • Dangers: Clogs water, inhibits other aquatic plants. Can tangle swimmers and restrict water usage

The Easy-Going Lifestyle of a Eurasian Watermilfoil

The Eurasian Watermilfoil is a very successful weed with a presence across the US, particularly in the thirty three states east of the Mississippi River. But it is not native to the US, having originally come from parts of Europe and northern Africa, from where it found its way to US in the 1940s.

It owes its success to a fast growth rate and a tolerant nature. It thrives well on extra warm water yet is able to overwinter in frozen lakes and ponds. Similarly, although it prefers lakes, ponds and slow-moving rivers or streams it does just as well in fast-moving water. It will also take to fresh spring water as well as to the brackish, salty water of tidal creeks and bays.

It helps, too, that the Watermilfoil reproduces through vegetative fragmentation and rhizomes or underground runners. The combination of huge size and fragmentation is what makes this weed such a hard act to follow for other weeds. In fact, it is a rare occurrence to find it in a setting where it is not a frustrating nuisance. It's mass of tangled stems choke the water, reducing oxygen levels for other plants and fish - and making it simply impossible to navigate or fish.

How to Control Eurasian Watermilfoil Weeds

Even by the stubborn standards of water weeds, Eurasian Watermilfoils are difficult weeds to contain. They tend to totally take over a lake or pond and travel far and wide on flowing water. Because of their sheer mass, mechanical harvesting is the quickest way to clear them out of a lake of pond. But that option is, of course, usually temporary because remaining fragments start a new colony and their fast growth rate compensates for any lost time.

There are herbicides that are quite effective against Watermilfoil but, as always, there is always the risk of contamination. The obstinacy and massiveness of the weed, however, has meant that plenty of scientific research has been directed at this weed. As a result there are a variety of insects that have been introduced that make a decent go at keeping the weed at bay. Interestingly, there are even some special fish species being deployed against the weed with reasonably good effect.

A new and potentially game-changing weapon against the Eurasian Watermilfoil is the Bottom Lake Blanket. This is one of our weed control products, made of specially formulated polyethylene that is 10 feet wide with no length limit. The blanket works by suffocating the weed by blocking away sunlight without affecting the fish or the water's chemical balance. It is lowered to a few inches from the water bed by strategically placed weights, pinning down the mass of weeds and whatever fragments may break off, while leaving space for fish to swim below and above the sheet.

Experience of using the blanket in over 400 lakes in over 29 states has shown that it totally destroys water weeds within four weeks - including the roots system. The Bottom Lake Blanket is now approved by the DNRs and DEPs of California, Nevada, New York, Connecticut, Massachusetts, Washington.

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