COURSE CARE
2015 Early Winter Disease Concerns January 20, 2015 By John H. Foy, director, Southeast Region

Is it Pythium or Microdochium patch? Only laboratory and microscopic examination can provide a truly accurate diagnosis.

Weather patterns with mild temperatures, high relative humidity, high dew points and extended periods of cloud cover are ideal for the development of turfgrass fungal diseases. A similar weather pattern currently is affecting areas in Florida and, not surprisingly, disease outbreaks have been observed. This update will describe common diseases being observed in the region. While your course may not currently be experiencing disease pressure, keep this information in mind because at some point conditions may occur that evoke the development of the following diseases.

 Bipolaris leaf spot disease has been problematic on courses in the central and southern part of Florida. Preventative fungicide applications have been required to avoid severe outbreaks and maintain dense, healthy turf. Generally, the use of contact fungicides applied on the shortest label-recommended interval has produced the most consistent and best results. Outbreaks of leaf spot disease have been noted on tees, fairway, and rough areas; but large-acreage fungicide treatments fortunately have not been required in most cases.

In mid-fall 2014 there were reported outbreaks of Rhizoctonia zeae sheath and leaf spot and – more recently – Pythium. Now some courses are experiencing difficulties with Microdochium patch – caused by Microdochium nivale, the same fungal pathogen that causes pink snow mold. While snow cover is a rare occurrence in the south, keeping putting greens covered during cold snaps can create the necessary environmental conditions pink snow mold outbreaks. When covers are removed, circular patches of light-pink mycelium produced by M. nivale may be seen if an outbreak of pink snow mold has occurred. Microdochium patch is the second phase of the disease and occurs in the absence of snow or covers. Very low light intensity, high relative humidity and cool-to-mild temperatures are necessary to trigger an outbreak of Microdochium patch.

However, during a discussion with Dr. Bruce Martin of Clemson University, he mentioned that it’s difficult to accurately diagnose Microdochium patch based solely on above-ground symptoms because they can be very similar to the symptoms caused by Pythium. Sending samples into a turf disease diagnosis lab is strongly recommended to make sure that the appropriate fungicide treatment is employed.

In addition to disease concerns, golfer complaints about wet, soft playing conditions and slower green speeds have been common. Superintendents are being accused of Overwatering when – in most cases – little or no irrigation has been applied over the past six to eight weeks. High relative humidity, high dew points, heavy cloud cover and periodic rain have prevented turf surfaces and soil from drying out.

The transition to the normally dry winter season in Florida has been delayed. Golfers need to understand and accept that until there is a change in the current weather pattern, nothing can be done short term to produce drier, firmer playing conditions.

Source: John Foy (jfoy@usga.org), Patrick O’Brien (patobrien@usga.org), Todd Lowe (tlowe@usga.org), and Chris Hartwiger (chartwiger@usga.org)

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