SURVEY QUESTION

SPORTS TURF: What disease do you target the most fungicide applications for?

Dollar Spot
Brown Patch
Pythium
Summer Patch
Spring Dead Spot
Other
None

Update (04/27/2015)

Big Focus on Large Patch

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Weather

Cool Down Brings April Back to Reality A.  Temperatures to April 26 and forecasted temperatures to close out April.  Forecasted temperatures should end April at approximately 3 degrees above normal.    - Source: Pat Guinan   B.  Soil temperatures and degr

The back half of April calmed the early April fire.  Temperatures expect to remain cool, and, if the forecast holds, April will finish approximately 3 degrees above average.  This is somewhat of a relief considering at mid April the state was 7 degrees above normal.   The NOAA climate prediction center has forecasted a warm early May in Missouri and much of the nation.  If this occurs, I expect that several pest and disease problems that had their metabolism kick-started in early April and suspended by cooler temperatures in late April, will rebound quickly and cause symptoms. 

Precipitation has been consistent throughout April, with the last 7 days, including yesterday’s event, having most areas receive 0.5 – 2.0” of rainfall.  The state is expected to dry out over the course of next week, which should be a relief to many in the region who have dealt with consistently saturated soils.  The saturated soils, and frequent April rains along with the cooler temperatures, may have set the stage for large patch, which is featured again in this update.     

Quick Hits

Missouri Frost Freeze Guide A new resource for planning when to plant frost sensitive plants in Missouri is available.

  • Frost/Freeze Website (click to view):  Dr. Patrick Guinan has scoured the last 120 years of data to historically define the growing season window from the last date of frost in the spring to the first date of frost in the fall.   Plentiful contour and point maps indicate median dates for temperatures of 24, 28, 32, and 36°F throughout the state, as well as the extreme latest or earliest dates for spring and fall frost events.  If you plant anything in Missouri, this should be a go to resource for scheduling your activities. 

  • On sites with previous history, billbug issues on zoysia should be considered now.  Curative control is challenging, and a preventive strategy targeted towards control of adults is suggested.  As mentioned in previous updates, zoysiagrass in Missouri is predominantly the cultivar ‘ Meyer’ due to its superior cold tolerance.  ‘Meyer’ is also unfortunately the most susceptible cultivar to billbug damage.   Previous research at U. of Arkansas found hunting billbugs were most active in late March and April, but some activity was observed throughout the whole year.  Complicating matters, several billbug species are present and may feed on zoysiagrass in Missouri, and their peak periods of activity and egg laying may be different.  The gddtracker.net website tracks the bluegrass billbug with a base 50 degree day model and indicates most of Missouri at or below I-70 is in the range of first adult emergence.  

Dollar Spot in Springfield Shortly after the previous update, a putting green sample with dollar spot was submitted from Springfield, MO. The dollar spot pathogen does not produce any spores, but has characteristic Y-shaped hyphal branching.     

  • Shortly after the previous update, a putting green sample of dollar spot was submitted to the plant diagnostic lab from the Springfield area.  Perhaps clouded by the recent aerification, the symptoms were a bit non-descript and could’ve easily been confused with Microdochium patch or anthracnose.  After incubation, copious amounts of mycelium covered the affected areas on the plug and Y-shaped mycelium of Clarireedia homoeocarpa (formerly Sclerotinia homoeocarpa) was observed covering and entering leaf tissue.  As noted in the previous update, the copious amount of rain we’ve had in April may be reducing the amount of available nitrogen, and rendering the bentgrass particularly susceptible.  If you applied a preventive application for fairy ring (see below), you should get a side benefit of some dollar spot control. 

  • The cool temperatures to end April kept us in the window for preventive applications targeted at fairy ring control on golf putting greens.  At this point, however, these applications should probably be down.  The subsequent low rate, watered-in DMI application should therefore be made in 21-28 days, hopefully outside the window of a potential high heat event.

  • Bermudagrass managers should be on the lookout for spring dead spot.  Several cases have been reported in Arkansas over the last few weeks.  If you do get the disease, the damage has been done, and fungicides will not be effective if applied at this time.  Map the outbreak, plan for fall prevention, and fertilize during the forecasted May heat spell to promote recovery.   

Large Patch Research

N Impact on Large Patch Severity The effects of nitrogen source and application timing on large patch severity is being investigated. Plates in the middle of plots are inoculation points. Sampling a large, large patch last week along the patch margin.

April showers bring May flowers and … large patch.  Several outbreaks of large patch have been reported and observed throughout Missouri in the last two weeks.  Below is a description of the research currently being conducted by M.S. student John Koehler, and a corresponding sample request for this research.      

Large patch on zoysiagrass is caused by the fungal pathogen Rhizoctonia solani AG2-2 LP.  Little research has been done on the effects of cultural practices, particularly nitrogen application timing and source, on large patch incidence.  Nitrogen applications during fall and spring are commonly avoided, due to concern of increasing large patch severity. No definitive correlation between nitrogen applications and increased large patch severity has been found, however.  Our goal is to determine if applying nitrogen during the spring and fall infection periods will increase large patch severity, or decrease it and promote disease recovery.  Along with application timing, we will also investigate the impact of different nitrogen sources on disease severity.  In our lab, we found that R. solani remained its characteristic brown color on media amended with calcium nitrate or urea, but on ammonium sulfate amended media was completely white.  Some fungal pathogens rely on dark brown melanin pigments to penetrate into plant cells, but the importance of melanin in R. solani infection of turfgrasses is not known.  The overall goal of this project is to integrate a nitrogen application strategy into the large patch management scheme. 

For this project, large patch samples from the region are needed.  If your golf course is near Columbia, MO I can visit to collect large patch samples.  For those who are farther away, it may be most feasible to make arrangements for shipping the samples.  If you choose to ship samples, follow the guidelines as you would for  sample submission to the turfgrass diagnostic lab.  In brief, cut an area of the affected turf from the margins of the disease, including 2/3 symptomatic and 1/3 healthy turf.  A cup cutter plug, or plugs 4-6 inches wide and approximately 2-3 inches deep, will be sufficient. Please also indicate the location (home address or golf fairway) the sample was taken from.  Please contact John via email (jfk7dc@missouri.edu) to set up the logistics for getting the sample to him.

Lee

Lee Miller
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Extension Turfgrass Pathologist
University of Missouri