Blue-green algae encroachment on bentgrass putting greens can manifest as a slime surface mat or a subsurface black layer.

With the ever-increasing demand for faster, more-competitive putting surfaces, superintendents are finding blue-green algae encroachment on bentgrass putting greens all too often. Excessive organic matter and moisture in the upper layers of the root zone accompanied with cultural and environmental stresses make golf greens an excellent growing medium for blue-green algae, various fungi and microflora.

Blue-green algae are prokaryotic organisms often referred to as cyanobacteria; but they differ from bacteria because they contain chlorophyll-a and release oxygen during photosynthesis (Bold and Wynne, 1985). Blue-green algae associated with turf decline have been identified asPhormidiumandOscillatoriaspecies (Tredway et al., 2006). However, because of the diversity of soil bacteria, other species can be involved and can potentially be apart of the blue-green algae problem. Research is being conducted to identify all the agents that comprise the blue-green algae complex and determine exactly which organisms are the true pathogen/weed problems on bentgrass putting greens.

Blue-green algae cause two distinct problems on putting greens: surface slime mats and subsurface black layer. The slime mats are described generally as scum or crust layers and range in color from green to brown or black (Baldwin and Whitton, 1992). Surface slime mats are the most common problem occurring on bentgrass putting greens. These mats disrupt the playing surface and create a soil medium unsuitable for bentgrass growth. They are a result of a mucilage substance that the blue-green algae secrete, which the organism uses for protection and conservation of water. When this slime dries, it creates a crust that is impermeable to water, limiting bentgrass growth (Turgeon and Vargas, 2006).

Blue-green algae, through these mats and fibrous growth, can clog soil pores and cause anaerobic conditions making the sand medium susceptible to subsurface black layer. When a soil becomes anaerobic, it allows sulfur-reducing bacteria to thrive and cause turf decline (Tredway et al., 2006).

Recent research identifies a new possible blue-green algae associated problem found on golf course greens: yellow spot disease. Identified on golf greens as yellowing small blotches, yellow spot disease is becoming a problem in the southeastern and western United States (Tredway et al., 2006). Though the disease does not pose a serious killing threat to turf stands, it does pose a problem with aesthetics.

Blue-green algae complex

Blue-green algae isolates taken in Knoxville, Tenn. Crust layers can range in color from green to brown or black.

A major factor for blue-green algae encroachment is water status. (Baldwin and Whitton, 1992). Persistent wet conditions favor blue-green algae development on putting greens (Turgeon and Vargas 2006).

A poorly drained root zone can increase blue-green algae encroachment, as well as pose a problem for bentgrass establishment and growth. Blue-green algae problems tend to occur in these poorly drained areas along with areas that are bare in the turf or where the turf stand is weak (Baldwin and Whitton, 1992). These bare areas can be a result of mechanical stress, such as areas where mower overlap and mower turn stress occur, poor seedling establishment, or perhaps areas distressed by disease.

Without competition from the bentgrass stand, blue-green algae growth can increase and expand over the entire golf green. Along with water issues, poor air circulation, which delays proper drying of the turf canopy, can increase the chance of blue-green algae encroachment as well.

In the turf market, there are numerous fungicide/algaecide control options that have been studied for control of blue-green algae on bentgrass putting greens. However, these control methods should be second to alleviating the conditions that are favoring blue-green algae growth.