Abstract/Contents: | "Once again, spring dead spot heads the list of the most important diseases of bermudagrass. Research conducted at the University of California Riverside has shown that Loptosphaeria korrae is one of the causes of this disease in California (2). Researchers in other parts of North America have tried techniques outlined by California researchers to isolate the causal agent but have not been successful. Spring dead spot can be a major problem in central North America (United States and Canada), southwest United States, southeast United States, eastern Australia and southern Australia. There have been several unanswered questions raised in the past year or so about the Rhizoctonia diseases. Brownpatch disease is not as simple as it once was. There are four species of Rhizoctonia which cause diseases of bermudagrass; Rhizoctonia solani, R. cerealis, R. oryzae, R. zeae (5). Although symptoms of disease may be different for each of these species under the same set of environmental conditions, the symptom expression may overlap considerably because of environmental conditions, virulence of the pathogen and turf growth conditions. Nuclear staining techniques are used to differentiate between these species in the laboratory (4). Rhizoctonia diseases occur as a minor problem in central North America (U. S. and Canada), southwest United States, and Egypt. Major disease problems have been reported in southeast United States, the Orient, eastern Australia, and Venezuela. Pythium diseases have recently had the spotlight in the turfgrass industry with the distribution of much literature on root disease and the limited success of control by some of the systemic fungicides. Although, Pythium has often been detected in roots of bermudagrass, most professional turf managers have not realized or have ignored the possibility of root damage. Rather, they were concerned with the blight symptoms characteristic of Pythium blight. Many species of Pythium are associated with bermudagrass with cool season and warm season species being important in turfgrass survival. New advances in epidemiology have made it possible to produce computer compatable, environmental data stations to help the turfgrass manager predict when to apply preventative fungicides. ELISA techniques are also being used to dipstick diagnosis for Pythium and will be available to the turf manager in a short time. Major Pythium problems have been reported on bermudagrass in the southwest United States, southeast United States, southern Australia, Venezuela, and a minor problem in central North America (United States and Canada). Nematode control is increasingly difficult in large areas with the removal of such materials as Ethylene dibromide (EDB) from the available pesticides. Materials such as Telone II are being testes but are much more costly than EDB. With the increased demand for quality turf, nematodes are becoming much more important. Data on thresholds in the southeast is sketchy. Much of the information on thresholds is borrowed but in many cases no one knows from where. Recently in Florida, a bacterium has been reported as a cause of bermudagrass stunting disease (1). This bacterium keyed with environmental stresses may lead to information related to bermudagrass decline." |