Over the last three to four weeks I have received pictures
from Neric Smith at Indian Hills CC (seen below), and also noticed dollar spot
on several creeping bentgrass golf course tees/fairways across the state. Dollar
spot is caused by the fungal pathogen
Sclerotinia homoeocarpa.
Generally, dollar spot develops when dew persists on the plant for greater than
8 hours. It is less dependent on temperature, and can develop over a wide range
of temperatures (55-80°F). Turf deficient in nitrogen is the most likely
situation where signs of dollar spot will occur. The disease gets its name from
the silver-dollar-sized blighted areas that appear on closely mown creeping
bentgrass. In Kentucky bluegrass and higher cut turf, the blighted area is
about the size of a softball. Upon further examination of the turf affected by
this disease, you will see an hour-glass shaped lesion in the middle of the
leaf blade. The lesion is tan in the middle, surrounded by brown to orange
halos on each side.
Active dollar spot infections produce a cottony white
mycelium mass that is often evident on the turf during the early morning hours,
not to be confused with spider webs. When viewed under a microscope the
mycelium will exhibit y-shaped branching and the presence of septum
(crosswalls). Pythium also produces this cottony white mass of mycelium but
does not contain septum.
There are many ways to control dollar spot. The most important management
technique is to increase N fertility in situations where N is found to be
deficient. In addition to adding nitrogen; moderating thatch, removing dew, and
preventing drought stress will help prevent the occurrence of dollar spot. The
risk with many site-specific inhibitors is the development of dollar spot
resistance. To prevent fungicide resistance use a rotation of chemicals and
avoid repetitive use.
The two pictures below were taken by Neric at Indian Hills.
Cutworms:
The black cutworm is the most widely distributed cutworm
that attacks turf in the United States. Cutworms do not overwinter in Iowa, but
are brought up by winds from the south. Once they are established in the
spring, they can undergo several life cycles before dying out in the fall. The
adult is a dark-colored moth that is often observed fluttering around lights in
the summer months.
Cutworms, as the ones seen below, are commonly found in open
aerification holes on golf course greens. A close look at the surface will
reveal a lot of feeding damage around the holes. They are often empty
because of the feeding of birds. Cutworms are surface feeders and can easily be
controlled with insecticides, the most common of these being Sevin (Carbaryl). While
the larvae mainly emerge at night to feed, some may be seen on the putting
surface during the day time, as was the case with the pictures below that
was seen at Cedar Pointe in Boone a few weeks ago.
