Blue green algae (Cynobacteria) develop on the surface of overly wet soils. Green or blue-green algae are lower plants that mat together to form a slimy green-black surface that when dry rolls and becomes crusty. Algae do not directly infect turf, but it is competitive in low density turf areas and inhibits important processes, like soil oxygen exchange by sealing the soil surface. From a sport’s playability stand-point algae can directly affect footing/traction, because it can become slippery.
Photograph 1: On this sports field a wet soil and a low density turf produce a favorable situation for algae invasion.
Environmental conditions that favor algae development include poor surface drainage caused by compaction or poor soils. If local weather conditions are warm, cloudy and wet then the problem is aggravated. Mowing a turf species too low and applying too much irrigation can also favor algae outbreaks.
Photograph 2: Close-up of the algae scum that has developed on the above sports field
* When the algae dries it cracks, curls and eventually goes away. To speed up the removal process, the dry algae crust could be diluted by verticutting and /or scarifying.
* Increasing turf density by slit-seeding desirable grasses into thin areas will help the recovery process
* Applying chemical algaecides does not address the reason why algae are there in the first place. The critical factor is to improve surface drainage through soil remediation practices, like core aerification and topdressing. However, there are fungicides (chlorothalonil or mancozeb) that are pretty effective control agents.
Photograph 3: Algae can produce a black scum that can seal the soil surface on putting greens.