News New Diseases Alert
Two newly emerging turf diseases, Rapid Blight and Brown Ring Patch, have recently been confirmed in samples received from golf courses in the UK and Ireland, and it is suspected that they are more prevalent in areas of fine turf than are currently recorded
DURING 2012, The Turf Disease Centre will be collating information on turf samples received for analysis that are positively identified with either of these two diseases, and a summary will be published later this year to show their recorded regional occurrence. The most important step in effective turf disease management is the identification of the cause and, with the apparent emergence of these new disease problems, this fact has never been more important.
Rapid Blight - A non-fungal disease
In 2004, turf samples were received from a golf course in the UK where the greens were showing a progressive decline in turf quality. Patches of affected turf, up to 30cm across, were becoming red/brown in colour, watersoaked in appearance and thinning out due to the loss of Poa annua and Agrostis spp from the sward. Analysis of the turf identified the presence of a non- fungal organism called Labyrinthula within the plant tissues, and a disease known as Rapid Blight was recorded for the first time in Europe.
Subsequent collaboration between The Turf Disease Centre and Dr Mary Olsen at the University of Arizona confirmed the identity of the organism as L. terrestris, a new species of Labyrinthulid, that Mary had initially identified in 2002, as the cause of this increasingly important turfgrass disease.
Over the past three years, The Turf Disease Centre has received a small number turf samples affected by Rapid Blight that have
originated from Ireland, Spain and Portugal, but it is believed that the incidence of this disease is much higher than has currently been recorded.
In Spain, the disease showed dramatic development of symptoms on creeping bentgrass greens (with patches up to 2m diameter) and extensive discolouration and turf loss on fairways (Fig. 1 & 2). The severity of the problem is correlated with not only the grass type that is present but also ambient temperature and the level of salinity in the rootzone or applied irrigation. Poa species are very heavily affected by this pathogen, as too are Lolium perenne and Agrostis spp. Warm-season turfgrasses can harbour Labyrinthula within the plant tissues, but they don’t show evidence of any disease. If these grasses are oversown with cool- season turf, the young seedlings inevitably become infected and disease symptoms will develop.
Symptoms can develop when temperatures rise above 15O
C
and salinity levels are >2.0dS/m (although Labyrinthula has been isolated from turf growing in much lower salinity conditions). Because the causal organism is not a fungus, most fungicides will have no effect, either on the organism or on the development of symptoms. However, research completed by Dr Olsen and other researchers across the USA has shown that the active ingredients - pyraclostrobin, trifloxystrobin and mancozeb - can provide effective control, but that results are much better if products are applied prior to or at the onset of disease, rather than curatively.
Close up of Brown Ring Patch (Waitea Patch)
In order for the correct product to be applied effectively, the presence of this Labyrinthula sp. must be accurately identified but, because it is not a fungus, L. terrestris can’t be cultured in the laboratory in the same way that fungi can.
During 2011, turf samples in which Labyrinthula was again detected, were received from golf courses in Ireland and the UK. In the UK, the symptoms on the affected course had been considered as being Anthracnose disease and managed accordingly (Fig. 3 & 4), but lack of recovery prompted an analysis that eventually identified the real problem. Due to the way in which Labyrinthula affects the plant, the sward initially becomes yellow, then becomes red in colour before the tissues eventually ‘rot’ and the sward thins. The symptoms can appear very much like Anthracnose (or Take-all Patch disease in Agrostis- dominated turf), but there will be no distinct blackening of the crown tissues, symptoms that are typical of Anthracnose Basal Rot.
Rapid Blight is considered to be a unique example of an emergent plant disease potentially induced by human activity (Douhan et al, 2009) and I am sure that, in the future, it will be confirmed on more amenity areas where water with high salt content is used for irrigation.
Now that we have learned how to identify this disease, sample analysis can confirm its presence
and, potentially, save significant management time and costs by allowing implementation of effective control options.
Detailed information on Rapid Blight disease can be found in the article Rapid Blight: A New Plant Disease, by Stowell, et al, 2005.
Brown Ring Patch - A non- fairy ring disease
During 2007, a sample received for analysis from a golf course in Portugal, was confirmed as having the fungal disease known then as Waitea Patch. This was the first known record of Waitea Patch in Europe.
The disease is caused by a Rhizoctonia-like fungus and, although the symptoms closely resemble those of superficial fairy rings or thatch fungi, this Rhizoctonia-like fungus is not related to fairy-ring causing fungi.
Since 2003, this new disease has been increasingly recorded on Poa annua turf across the USA and, more recently, on Poa trivialis (Wong & Kaminski, 2007). However, prior to the recognition of this problem in the United States, the disease was first recorded as developing on Agrostis palustris turf in 1994 in Japan (Toda et al, 2005) where the symptoms developed as brown rings and was given the common name of Brown Ring Patch.
On Poa annua, the affected turf shows symptoms of coalescing
Fig.1. Rapid Blight on creeping bentgrass in Spain
6 PC APRIL/MAY 2012
Fig. 2. Fairway damage caused by Rapid Blight in Spain
Fig. 3 Rapid Blight in the UK, 2011 (photographs courtesy David Stansfield, David Stansfield Ltd)
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