Diagnosis is often made difficult by symptoms that differ from published descriptions or by the similar appearance of several diseases, particularly the numerous patch diseases reported on Kentucky bluegrass. Further confusion sometimes arises because the symptoms of some diseases and nematodes resemble those of poor site adaptation, shrub and tree competition, low fertility, root-feeding insects, soil compaction, and other sources of turf stress. Before arriving at a diagnosis, carefully examine the affected turf and management records to eliminate other possible causes of turf problems. For a positive diagnosis, you may have to submit a plant or soil sample for nematode analysis to a professional laboratory. The susceptibility of most turfgrasses to disease is influenced by management practices such as fertilizing, removing thatch, mowing, and watering.
Diseases are often most damaging to over-fertilized, intensively managed turfs.
However, some diseases are restricted to low-management turfs. Turf nutrition plays an important role in the development of several common diseases. Rust, dollarspot, leaf spot, and crown rot are more severe on turf that is stressed by low nitrogen or potash levels. The overuse of nitrogen fertilizers greatly increases the susceptibility of turf to brown patch, Pythium blight, spring dead spot, and gray leaf spot. An early spring or fall nitrogen application increases the risk of a brown patch outbreak, especially in the coastal areas of Alabama.