Algae scum keeps grass away.

Superintendents are finding blue-green algae encroachment on putting greens an all-too-common theme. 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 micro-flora. Blue-green algae are prokaryotic organisms often referred to as cyanobacteria; however, because of the diversity of soil bacteria other species may be involved and could potentially be a part of the blue-green algae problem.

Blue-green algae are known to cause two distinct problems on putting greens: surface slime mats and subsurface black layer. The slime mats have been described generally as dark scum or crust layers and range in color from green to brown or black.

A major factor for blue-green algae encroachment is water status. Persistent wet conditions favor blue-green algae development on putting greens. A poorly drained root zone can increase blue-green algae encroachment, as well as pose a problem for grass establishment and growth. Problems tend to occur in these poorly drained areas along with areas of bare turf or where the turf stand is thin or weak.

Cultural Controls

In the turf market are numerous fungicide/algaecide control options have been studied for control of blue-green algae on putting greens; however, these control methods should be second to alleviating the conditions that are favoring blue-green algae growth. Water management should be one of the first cultural practices considered when trying to remedy algae encroachment. Drainage and excessive subsurface water retention should be improved in order to decrease anaerobic conditions and improve turfgrass vigor. Air circulation should be enhanced around the surrounding area to increase water evaporation and maintain adequate subsurface water levels. Cultivation methods such as aerification or spiking should be used to break up the blue-green algae crust and allow water and air circulation into the root zone (Turgeon & Vargas 2006). Topdressing can also be utilized to coat the algal mat and help to break up the crust layer. Blue-green algae are photosynthesizing organisms, so a layer of sand above the photosynthetic tissue can create a stress on the organism allowing grass to compete. Once conditions that favor blue-green algae growth have been corrected, over-seeding as well as chemical control may be considered.

Chemical Controls

Various fungicides/algaecides are available for blue-green algae control. Mancozeb (Junction, Fore), Chlorothalonil (Daconil Ultrex, Daconil Zn), Hydrogen Dioxide (ZeroTol) and Copper Hydroxide (Kocide 3000) are some examples that are labeled for the control of blue-green algae in turf. According to Dernoeden and Shmitt (1992), chlorothalonil is effective for blue-green algae control, and different formulations did not change effectiveness. Elliot (1998) also noted this same result in a study with different formulations of chlorothalonil on bermudagrass putting greens. Mancozeb and chlorothalonil will effectively suppress development of blue-green green algae on putting greens (Elliot, 1998). When these chemicals were tested as preventive instead of curative applications, better results were observed, and both chlorothalonil and mancozeb were able to restrain the encroachment of blue-green algae on bermudagrass putting greens (Elliot, 1998). According to Elliot (1998) mancozeb and chlorothalonil can both be used as an effective preventive of blue-green algae encroachment. Chemical control should always be secondary to alleviating environmental and cultural factors contributing to blue-green algae encroachment. Monitoring weather patterns and applying these chemicals as labeled can help to prevent blue-green algae from encroaching onto golf course greens.

See also LSU Turfgrass Disease Guide