Don't Spread Didymo

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Boulder Booger

This invasive species of algae, commonly known as "rock snot," forms large mats on the bottoms of lakes, river and streams.

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Didymo

Didymosphenia geminata, an invasive algae, forms slimy mats that smother fish eggs and makes water sports unpleasant.

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By Any Name, This Invasive Alga is Just Plain Slimy

Rock snot. Sounds a lot worse than “Didymosphenia geminate,” doesn’t it? This invasive alga is also commonly known as “didymo,” but no matter what you call it, it's gaining footholds in streams worldwide, including some of the most revered trout waters on Earth. The infestation nearest to Missouri is in the White River just south of the Missouri-Arkansas border.

Bad News for Anglers

The jury is still out concerning didymo’s possible ecological effects. But rock snot is definitely bad news for anglers. Stringy alga threads catch on all types of hooks, from dry flies to crankbaits, making fishing nearly impossible.

Please Control Didymo, Comply with the Porous-Soled Wader Ban and Wash your Waders!

Contamination of recreational equipment, such as boats, life jackets and fishing gear, particularly waders, is the most common way for didymo to spread. Please help us keep didymo out of Missouri.

• Follow the control recommendations in Didymo Control below.
• Comply with the new porous-soled wader ban, which goes into effect March 1, 2012. See ban details in Porous-Soled Wader Ban below.
• Treat your porous-soled waders to avoid spreading didymo in Missouri. This video shows you how.
• Wader-Washing Locations below shows you where to find wader-washing stations at your favorite Missouri trout park.

Didymo Control

This fact sheet shows you how to identify and control didymo, a type of invasive algae commonly known as "rock snot." which can cover stream bottoms, smothering fish eggs, degrading water quality and affecting fishing success.