This very slimy substance (Fig. 1) has many common names, was once classified as an algae but is now known as a Cyanobacterium. It is worse in areas that are frequently wet, such as low areas in lawns or on frequently irrigated golf courses (Fig. 2) or along walkways in nurseries where it can create a slipping hazard. However, it can show up in a wide range of locations, including on driveways and in parking lots. Nostoc will dry out during periods without rain, which can make it somewhat easier to scoop up and remove the blackened material (Fig 3).
- Improve drainage where practical.
- Avoid using too much fertilizer, especially phosphates, on lawns nearby. Phosphate fertilizers can increase the growth of the algae and Cyanobacteria. Do a soil test and apply only enough fertilizer to keep the lawn healthy.
- When Nostoc is dry pick up what you can, bag and dispose of it. (Raking may spread it further)
- When working around Nostoc take care to clean shoes and tools afterward to avoid moving it to new locations.
There are limited options for chemical control of Nostoc in turf and little research has been done on the topic. Homeowners can try Bayer Moss and Algae Killer, Safer Brand Moss and Algae Killer, and Garden Safe Moss and Algae Killer Concentrate (or other similar products that contain potassium salts of fatty acids). Remove what you can first then treat when the area is moist and the green material is soft. Because Nostoc produces copious amounts of slime, it is difficult for treatments to penetrate into the living parts of the blobs and several repeat treatments may be needed. This type of treatment is usually only temporary. The best permanent solution is to reduce moisture and excess phosphorus that promote growth of this slimy mess.
For more photos and background information:
For management in the nursery: