This winter look out for leaf spot on bermudagrass
One of the most chronic and devastating diseases of bermudagrass greens during late-fall and winter is leaf spot. In South Florida for example, leaf spot often peaks in January. The disease requires early diagnosis and often repeated treatments for control.
Figure 1: Close-up of the leaf spot symptoms on a bermudagrass (utradwarf) green.
Cool, wet weather is ideal for the development of leaf spot on bermudagrass. The disease appears as small brownish spots normally one to two inches in diameter. The spots may coalesce forming large blighted areas. Symptoms on greens are most apparent along the outer edges of the bermudagrass green where traffic wear from mowing is the greatest. Leaf lesions appear as a bleached or whitish center surrounded by a purplish border.
Figure 2: Typical bermudagrass leaf spot symptoms caused by Bipolaris leaf spot.
In the past, The pathogens that cause this disease were grouped as Helmithosporium leaf, crown and root diseases. Golf Course Superintendents often still refer to it as Helminthosporium leaf spot. However, the pathogens that are associated with bermudagrass leaf spot are the Bipolaris species (ex. B. cynodontis, B. spicifiera, and B. sorokiniana). The most prevalent pathogen on bermudagrass is Bipolaris cynodontis but other Bipolaris species can infect too. The common name for the disease now is Bipolaris leaf spot.
Figure 3: Close-up of the coelescing and expansion of the leaf spot symptoms.
Cultural practices that may help reduce disease severity include fertilizing to promote moderate growth, but not over stimulating growth, reducing thatch, increasing sunlight by removing or pruning trees if the turf is shaded and proper irrigation. Herbicide applications including both pre-emergent and broadleaf weed chemicals during leaf spot activity may increase disease severity.
Figure 4. Overview of the leaf spot symptoms on a putting green. In this case, the turf is seashore paspalum.
Fungicides applied preventatively and repeatedly when conditions are favorable for Bipolaris leaf spot are needed. Secure® Action™ or Daconil® Action alone, tank mixed or in rotation are effective for Bipolaris leaf spot control.
For further information for controlling bermudagrass diseases, including leaf spot during cool wet weather, see this technical article from Lane Tredway, technical services manager for Syngenta, entitled “Protect your bermudagrass greens now to maximize spring quality”.
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: