View source for Gloeocercospora sorghi (copper spot of creeping bent grass)

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'''<big>Lee Miller, University of Missouri</big>'''

'''Reviewed by:Name, Organization'''
=Pathogen=
Gloeocercospora sorghi is an ascomycete with no known teleomorph. The pathogen produces abundant sporodochia that emerge through stomates on the leaf surface.  Sporodochium bear numerous conidia in a salmon-colored slime.<ref name="smiley"/>  Conidia are hyaline, needle-shaped, have 1-7 septations, and are 20 – 195 μm long and 1.4-3.2 μm wide.  Small, black sclerotia (0.1-0.2 mm diameter) may be observed in necrotic leaf lesions.    

=Symptoms and Signs=
In the early stages of disease, lesions are small and reddish but enlarge to cover the entire blade. Since the disease occurs most often on low mown putting greens, the stand symptom is often first observed in the field. Copper to reddish-pink colored patches approximately 1-3 inches in diameter.  In warm wet weather, or dew events leaves may be covered with mycelium and/or a gelatinous matrix of salmon-colored spores.<ref name="smiley"/> 
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=Ecology and Spread=
G. sorghi overwinters as sclerotia and thick mycelium in thatch. Initial infection occurs at air temperatures of 68°F. Hyphae germinating from sclerotia penetrate leaf tissue through direct penetration or through stomates.  Masses of conidia formed by sporodochia are distributed to other leaf surfaces by splashing water.  The pathogen can produce secondary inoculum rapidly in conducive temperatures of 79-86°F and extended periods of wetness, resulting in large epidemics.<ref name="couch"/><ref name="smiley"/>

=Geographic Distribution=
Copper spot occurs mostly on Agrostis spp., and is particularly prevalent in the northeastern U.S. on Agrostis canina.  Recently, more outbreaks have been observed on A. stolonifera in the central U.S.   The pathogen also causes zonate leaf spot in numerous other Poaceae, which is also an important foliar disease on sorghum.<ref name="smiley"/>    
=Cultural Control=
As with other foliar diseases, minimizing leaf wetness duration through early morning mowing, irrigation, dragging a hose, or dew-whipping can aid in preventing copper spot development.  In active infections, however, do not mow or move morning dew across the green as this will aid in conidia spread. Also limit the use of water-soluble nitrogen sources when copper spot is active.  Maintaining a soil pH between 6 and 7 is ideal to suppress copper spot.<ref name="vargas"/>

=Host Resistance=
No information on resistant cultivars is available.<ref name="vargas"/>

=Diagnostic procedures=
Copper spot and dollar spot may occur simultaneously on Agrostis.  Copper spot, however, is a darker brown to rust colored, while dollar spot symptoms are typically a bleached color.  Copper spot stand symptoms may also resemble red leaf spot and the initial stages of brown patch.  The most characteristic diagnostic feature of copper spot is the numerous filiform shaped spores, which are formed en masse on leaves and easily found when examined under a compound microscope.  If the sample is dry, an overnight incubation in a humidity chamber at room temperature will cause pathogen sporulation.    

=Resources and References=
<references>
<ref name="couch">Couch, H. B. 1995. Diseases of Turfgrass, 3rd edition. Krieger Publishing Company. Malabar, FL.</ref>
<ref name="smiley">Smiley, R. W., Dernoeden P. H., & Clarke, B.B. 2005. Compendium of turfgrass diseases. The American Phytopathological Society. St. Paul, MN.</ref>
<ref name="vargas">Vargas, J.M. (1994). Management of Turfgrass Diseases. Lewis Publishers. Boca Raton, FL. </ref>
</references>

=Acknowledgments=
{{NorthCentralDiagnosticResources}}
[[Category:Diagnostic Resources]]