Algae in Turfgrass

Algae are primitive green plants. They can be a problem in turfgrass when surface conditions are overly wet. They tend to occur in low, shaded, or compacted areas. Algae form a greenish to black scum on the soil or in thin turf. As this blackish scum dries, it appears as a crust that later cracks. Turfgrass plants may become chlorotic (yellowed), weak, and eventually die.

Algal scums can be controlled by:

  • improving surface and subsurface drainage
  • avoiding frequent waterings, especially at night
  • aerifying compacted areas
  • maintaining proper pH and nutritional levels
  • increasing mowing height
  • improving light penetration to the turf
  • using shade tolerant grasses in shady areas

Algaecides or fungicides can help control algae problems when wet conditions are also corrected. For up to date information on recommending fungicides, visit "Chemical Control of Cooperative Extension Service Turfgrass Diseases" available for free at this link. Remember always read and follow pesticide labels.

Originally prepared by Paula Flynn, updated by  Lina Rodriguez Salamanca

Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on September 14, 2018. The information contained within may not be the most current and accurate depending on when it is accessed.