Abundant algae has been observed on several golf turf samples submitted to the UMass Extension Plant Diagnostic Lab this season. Terrestrial algae (cyanobacteria) are natural inhabitants of the soil and can proliferate under moist conditions. These organisms secrete a matrix of sugars that protects them from heat and drought. Algal proliferation appears as a slimy, dark green to almost black layer that covers the lower turf canopy and soil surface. This layer can turn to a hard crust when dry. Algae is a most often a problem of low-cut, intensely managed turf typical of golf courses and is therefore highly unusual on healthy lawns.
Algae love warm, wet/humid weather, high fertility (especially phosphorus), and poorly drained soil. Excessive algae appears in areas where the turf canopy is thin, a common problem in late summer, particularly in high traffic areas and places where the soil may be compacted. In areas where turf is thin, algae can take advantage of the sunlight that reaches the soil surface. Algae can be especially problematic in areas that experience afternoon shade, which prevents the turf canopy from drying out.
Algae compete with turf for light and nutrients and exclude oxygen from the lower turf canopy and root zone. There is also some evidence that some species of algae produce toxins that inhibit turf growth. Turf inhibited by algae may begin to yellow from the bottom up and thin out.
Several products are available for management of algae on golf greens; however, chemicals alone cannot be relied upon for sufficient algae control. Good cultural practices must also be implemented. These include:
- Water management and good drainage. Aerify, topdress, and water deeply and infrequently.
- Reduce fertilizer input where possible, especially phosphorus.
- Increase air circulation and sun exposure.
Chlorothalonil is commonly used to manage algae on putting greens. Other choices include copper, mancozeb, and hydrogen peroxide. Check labels carefully as not all products are labeled for algae. Preventive applications are always better than curative ones, so begin in early summer. Some turf managers have found that it is more effective to apply chemicals to turf when it is dry. Since repeated applications of copper can result in accumulation of toxic levels in the soil, copper products should be considered as a last resort. When making curative applications, avoid overuse of DMI fungicides as they have plant growth regulator effects and can hinder turf recovery.
Submitted by: Dr. Angela Madeiras