Tar spot on seashore paspalum in Georgia
Tar spot has been identified for the first time on seashore paspalum turfgrass at the University of Georgia.
Alfredo Martinez-Espinoza, Ph.D.; Omar Martinez-Uribe; and Dae Kim
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is a warm-season grass native to tropical and subtropical regions of North and
South America. In the United States, it is found in the coastal regions of
Texas, Florida, Georgia, South Carolina and North Carolina. With the exception
of one commercially available seeded cultivar, seashore paspalum propagates via
rhizomes and stolons. Seashore paspalum has been growing in popularity for use
on golf course tees, fairways and greens because of its high tolerance to
saline soils and water (3,8).
Figure 1. Tar spot lesions, which were black to dark brown with
yellow to light brown tissue surrounding the spots, were discovered
on seashore paspalum plants in a greenhouse at the
University of Georgia in Griffin, Ga.
Photos by Alfredo Martinez
Symptoms on plant tissue
spot was first observed on seashore paspalum turfgrass plants in late 2010 at a
research greenhouse on the campus of the University of Georgia in Griffin, Ga.
Symptoms of the disease included what were later determined to be tar spot
lesions, which were black to dark brown with yellow to light brown tissue surrounding
the spot (Figure 1). The spots were small and compact, and most were circular to
slightly oval. Some spots coalesced and formed a short delineated strip (Figure
2). Spots were located mainly on the tops of the leaves, with some
discoloration on the back of the leaves. However, tar spots did not reach the
back tissue of the leaves. These observations are consistent with tar spot
disease observed in other turfgrasses, and in other crops, where lesions are
dark, small, compacted and located on the upper part of the leaves (Figures 1,2)
(1,2,4-7,9-11). Clypei. Light and electron microscope observations conclusively
showed that the lesion on the paspalum plants was made up of a shield-like
structure called the clypeus (plural clypei) (4,7,10,12). The clypei are oval in shape with
a slightly raised center and seem to push through the epidermis of the plant
tissue, dramatically changing the structure and anatomy of the plant epidermis.
The size of clypei ranges from 170 micrometers × 152 micrometers to 203
micrometers × 495 micrometers.
Figure 2. Some of the tar spots coalesced to form a continuous strip on the grass blade
Figure 3. An electron microscope photo shows an ascocarp, which forms a nest-like or spherical supportive structure for asci, the bean-pod-like structures that contain the ascospores by which the tar spot fungus reproduces.
Figure 4. A light compound microscope photo shows an ascus containing eight ascospores arranged in a single row.
Figure 5. An electron microscope photo with a close-up of ascospores, the fungal spores from the tar spot fungus.
Figure 6. The reproductive spores (ascospores) of the tar spot fungus are seen breaking through the tissue of an infected seashore paspalum plant to infect other plants.
and asci. An
a nest-like or spherical structure that contains the asci (plural of ascus),
bean-pod-shaped structures that are the sexual spore-bearing cells produced by
ascomycete fungi (12) (Figure 3). When seen under an electron microscope, the asci
are cylindrical and arranged in a palisade formation with vegetative tissue
dispersed throughout the ascocarp. The asci range from 7 to 8 micrometers in
width × 48 to 51 micrometers in length.
individual ascus containing eight ascospores (fungal spores) is shown in a light
microscope photo (Figure 4). The ascospores are uniseriate, that is, they are
arranged one by one in a single row (12). The ascospores also have a smooth
surface and are devoid of any ornamentation (Figure 5). Their shape is ellipsoidal,
and many of them have a slightly conical or parabolic end. No division,
separation or any other structure was observed. Ascospore size ranges from 5.7
to 7 micrometers in width × 10 to 11 micrometers in length. In an electron
microscope photo, masses of ascospores are shown oozing through small ruptures or
holes in the clypei; ascospore release appears to be limited to the inter-vein
sections of the leaf (Figure 6).
fungal organism can only grow on living tissue. After evaluating several
methods of infecting the turfgrass and determining the environmental conditions
conducive to infection, we collected grass clippings from the infected source
(initial infection was observed in the cultivar SeaIsle 2000). Infected grass clippings
were placed on healthy seashore paspalum turfgrass grown in plastic pots in the
greenhouse. Greenhouse temperatures were kept at 77 F-80 F (25 C-27 C) and high
careful visual evaluation of physical symptoms was conducted. Plants were
inspected for size, shape, color, appearance, distribution, quantity and
location of le- the lesions and observed under a compound microscope and under
electron scanning microscopy. Visual observations, light microscopy and
electron microscopy yielded conclusive evidence of the pathogen infection and
process was replicated at least four times. Healthy plants of the cultivars
SeaIsle 2000, Aloha, SeaIsle Supreme and an experimental line (106L-1) were successfully
infected with tar spot. All the inoculated pots were infected, but the
incidence of the infection was rather low (mean of 5%).
ascocarp, asci and ascospore morphology and measurements corresponded exactly to
those described for Phyllachora paspalicola (also known as Phyllachora
grass was infected with P. paspalicola isolates, fulfilling Koch’s postulates
and demonstrating the causal agent of the disease. Therefore, we propose that
the causal agent of tar spot in seashore paspalum is P. paspalicola. To our
knowledge this was the first report of tar spot on seashore paspalum in
The research says
- Visual observations, light microscopy and electronic microscope
techniques yielded conclusive evidence of the pathogen infection and symptoms.
- Fungal morphology and measurements corresponded exactly to those
described for Phyllachora paspalicola.
- Healthy grass was infected with P.
paspalicola isolates, demonstrating that P.
paspalicola is the causal agent of tar spot in seashore paspalum.
material in this article was adapted from Martinez-Espinoza, A.D., Martinez- Uribe,
O. A., and Kim, D. 2012. Identification and characterization of tar spot on
seashore paspalum in Georgia. (Abstr.) Phytopathology 102(Suppl.):S4.76,
and was also taken from the accompanying poster as presented at the 2012 Annual
Meeting of The American Phytopathological Society, Providence, R.I., Aug. 4-8,
- Bockus, W.W., R.L. Bowden, R.M. Hunger et al. 2010. Compendium of Wheat
Diseases. APS Press, St. Paul, Minn.
- Dakshini, K.M.M., R.K. Tandon and K.G. Mukerji. 1970. A new species of Phyllachora.
- Duncan, R.R., and R.N. Carrow. 2000. Seashore Paspalum—The Environmental Turfgrass.
John Wiley & Sons, Hoboken, N.J.
- Hanlin-Silva, D.M.W., and R.T. Hanlin. 1998. The order Phyllachorales:
Taxonomic review. Mycoscience 39:97-104.
- Monteiro, F.T., B.S. Vieira and R.W. Barreto. 2003. Curvularia
Two fungal pathogens of the grassy weed Hymenachne amplexicaulis from
Plant Pathology 32:449-453.
- Orton, C.R. 1944. Graminicolous species of Phyllachora in North
- Parbery, D.G. 1967. Studies on Graminicolous Species of Phyllachora
in FCKL: A taxonomic monograph. Australian Journal of Botany 15:271-375.
- Raymer, P.L., S.K. Braman, L.L. Burpee et al. 2008. Seashore paspalum: Breeding
a turfgrass for the future. www.usga.org/turf/green_section_record/ 2008/jan_feb/breeding_future_turfgrass.pdf
- Rey, M.E., and H.M. Garnett. 1984. A physiological study of Panicum
Journal of Botany 62:2283- 2289.
- Silva, D.M. 1996. Phylogenetic relationships of the Phyllochorales and related
genera. Ph.D. diss. University of Georgia, Athens, Ga.
- Smiley, R.W., P.H. Dernoeden and B.B. Clarke. 2005. Compendium of Turfgrass
Diseases. APS Press, St. Paul, Minn.
- Ulloa, M., and R.T. Hanlin. 2012. Illustrated Dictionary of Mycology. APS
Press, St. Paul, Minn.
Alfredo Martinez-Espinoza, Ph.D., is an associate professor in plant pathology at the
University of Georgia-Griffin; Omar Martinez-Uribe is a student at the University
of Georgia, Athens, Ga.; and Dae Kim is a student at Georgia State University,