symptoms appear as roughly circular patches of tan turf that can
sometimes partially fill in with weeds or grass to create 'frog-eye'
patches (Figure 6). The key difference, however, lies in the active
temperature range of each disease. Whereas necrotic ring spot
only infects when soil temperatures are between approximately 55
and 65°F, the summer patch fungus BEGINS to infect roots once
soil temperatures reach approximately 60°F.
As the soil temperatures rise through summer the fungus infects more and more turfgrass roots until sometime in mid-summer when the remaining functioning roots cannot support the
plant and it wilts and dies. A fungicide application once symptoms have appeared will stop the current infection from spreading
(assuming you get the fungicide down into the roots). However,
because the infection decimated so much of the root system, the
symptoms are likely to persist and the plants weakened for the rest
of the summer. Methods for reducing summer patch infection include healthy rooting practices (summer patch is worse where
thatch is excessive and in poorly draining or compacted soils) and
reducing the soil pH to under 6.5 through acidifying fertilization
or other means. Where summer patch is a consistent problem,
fungicides from the strobilurin or DMI class can be used and
should be applied in the late spring when soil temperatures are approaching 60°F. Care should be taken to water the fungicides into
the top inch of the soil where the fungus is active.
www.stma.org
The aforementioned diseases are not the only diseases you will
find on your athletic field, and even determining which disease is
present on your turf (or if it's a disease at all!) can be very taxing.
If you're unsure, I recommend submitting a sample to a diagnostic
lab that specializes in turfgrass diagnostics to confirm the presence
of a disease PRIOR to applying a fungicide. It's better to spend
$100 on proper diagnostics than waste $500 on a misapplied fungicide. Many universities around the country, including the Turfgrass Diagnostic Lab at Wisconsin (www.tdl.wisc.edu), have
excellent turf diagnostic facilities and can provide needed support
to properly diagnose your problem. For the most effective chemical control options check with your local sales representative, extension agent, or look up the University of Kentucky's "Chemical
Control of Turfgrass Diseases 2013" online. n
Paul Koch, PhD, is an associate researcher, turfgrass pathology, at
the University of Wisconsin-Madison.
SportsTurf 23
