Didymo, Rock snot Didymosphenia geminata

Brown, tan or yellow mat of algae at the bottom of water body

  • English Name: Didymo, Rock snot
  • Latin Name: Didymosphenia geminata
  • Propogate: Vegetative fragmentation
  • Symptoms: Brown, tan or yellow mat of algae at the bottom of water body
  • Dangers: Covers fish eggs, degrades water quality, affects fish food and fishing

Survival Tactics of Rock Snot Water Weed

Didymo is not native to America. It is a northern Europe import that has since settled successfully across most of the US. Young colonies of the weed are harmless and almost pleasant looking "pimples" on submerged rocks or water beds, but when they get going, they form impenetrable mats of unsightly "snot" that can get eight inches think. Few other plants can survive the onslaught.

The trick to this weed's survival success is that it is a perennial plant that grows through the seasons and multiplies vegetatively from fragments of mature plants. Rock Snot also has the advantage of being able to live in water with little nutrients, plus sticking to the bottom of water bodies where it is harder to be reached by animals or birds.

But the weed's real secret weapon is that combination silica body content and dead mucus. Few animals or birds find that mix appetizing. Also, the combination makes it easy for just about anything that comes into contact with the weed to serve as a carrier to new territory. It is also what gives the weed the ability to stay alive for month in a dry environment such as the side of a boat, fishing equipment or shoes soles.

The only major weakness that Rock Snot has is that it requires shallow water so as to get enough sunlight.

How to keep Didymo Rock Snot weeds in Check

Didymo weeds are a nuisance wherever they take hold. They basically smother the entire river bed, making it near impossible for other weeds to grow and even covering fish eggs. Fishing is difficult where the weed is well established and, of course, swimming in "snot" is not an inviting prospect. Fortunately, the snot does not pollute water in the sense of making it undrinkable although people swimming downstream of a big Rock Snot colony may suffer some eye irritation.

The standard way of getting rid of the Didymo snot is to dredge it out. The method rarely eradicates the weed totally because whatever tiny parts of it that remain behind starts a new colony. A more effective method is to use the Bottom Lake Blanket. This is our lead weed control product and possibly the only method that can in fact totally eradicate a rock snot colony.

The Lake Bottom Blanket is made of 10 feet wide sheets of specially formulated polythene that can be cut to the length of any particular water body. It works by floating slightly above the water bed - on account of being made of material that is lighter than water and a set of weights to keep it in place. Fish and other aquatic animals are not affected since they can freely swim below and above the Blanket. It destroys the entire colony of weeds by simply denying them any sunlight.

The Lake Bottom Blanket is approved for use by the DNR's and DEP's of California, Nevada, New York, Connecticut, Massachusetts, Washington - and has already been used in over 400 lakes in over 29 states.

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