We have recently received many questions concerning problems in bermudagrass hay fields and pasture land.
Across the Southeast, many producers that have not seen problems in the past are seeing them this year. They describe a “dying” or “browning-off” of their bermudagrass.
The question everyone wants answered is, “What is going on in my field?”
Bermudagrass leaf spot is characterized by brown, black or faded circular lesions on leaves, which are most prevalent around the collar of the leaf blade. It has been linked to a Bipolaris fungus. Beginning as spotty patches randomly-located around the field, leaf spot can spread to form large irregularly-shaped areas that result in decreased yield and thinning of stands.
If the browning or spotting moves from the leaf blades onto the bermudagrass stolons and rhizomes and/or crown area, damage could be devastating to the stand.
Leaf spot requires several hours of continual leaf wetness to really thrive. As such, it is no surprise this disease has become so prevalent in this summer of excessive and abnormally frequent rainfall.
Moreover, leaf spot problems are most severe when bermudagrass gets overly mature and/or lodged.
Bermudagrass leaf rust, also referred to as Puccinia, is represented as small, red to orange lesions, clustered and abundant in quantity, found on leaf and stem tissue.
Lesions begin as raised areas on the leaves and can easily be felt by rubbing a leaflet. Plants infected with rust can potentially leave “rusty” coloration on your hands and clothing and is therefore easily identified.
Leaf spot and leaf rust are often confused with one another. Microscopic identification can determine which of the two diseases is in fact causing the problem, but the management approach is virtually identical.
Bermudagrass varieties that are not as resistant as other varieties to these diseases can be the first problem. When preparing to establish new plantings of bermudagrass, select hybrid varieties (e.g., Tifton 85, Russell, Coastal, Tifton 44, etc.) that exhibit some level of disease resistance.
Annually, most reports of leaf spot/rust are in common bermudagrass varieties or other varieties that are known to be susceptible (e.g., Alicia, World Feeder, etc.).
This year, even resistant bermudagrass varieties are exhibiting significant signs of disease.
Low soil potassium levels in bermudagrass have been linked to increased disease and decreased stand. If soil tests do not recommend potash application and disease symptoms are still apparent, collect forage samples to determine potassium levels through tissue analysis.
Other management considerations include timely harvest, minimized thatch, and water management.
There are no chemical control options for leaf spot/rust. Regularly burning bermudagrass fields in late February or early March at least one out of every three years can drastically reduce the incidence of these disease problems because it reduces the residual forage that hosts the spores.
Removing infected material and fertilizing to overcome nutrient deficiencies are currently the only options found to be effective to control leaf spot/rust.
For more information about managing these disease problems in bermudagrass, see the UGA Cooperative Extension publication entitled “Leaf Spot Diagnosis and Management in Bermudagrass Forages” (C 887) at http://www.caes.uga.edu/Publications/pubDetail.cfm?pk_id=7386.