Late May has heated up with above normal high and low air temperatures over the last 3 days. Soil temperatures have followed suit This high temperature trend is forecasted to continue into late May and early June (see below), which could spark off our first round of heat stress for cool season turfgrasses… and associated summer diseases.
As noted in the last report, precipitation has been below normal in May. May is typically our wettest month with the state averaging approximately 5” of total precipitation. Some areas in SW and central Missouri are 3” and almost 4” below normal for the month. Luckily, or unlucky for farmers trying to plant, April had above average precipitation (6th wettest on record). This dry May, however, may be an issue, and echoes the 2012 drought when a hot, warm May rolled right into a bone-dry summer. Fortunately, this week and early July looks to produce isolated, or scattered PM storms across the region. Let’s hope they are not so isolated and not quite so scattered.
In the last few weeks, three cases of Pythium root rot have been diagnosed on putting greens samples sent in from STL and KC. Most of these samples were waterlogged from previous rains or irrigation events and had high organic matter. The disease can be caused by a number of different Pythium spp., and does not need to be sparked by a wave of extreme >90F temperatures to cause decline. Basically, all the pathogen needs is a pool to swim in (aka saturated soil profile) caused by rainfall or irrigation events. The disease also takes advantage of a hole in many greens fungicide programs, as most do not include a watered in fungicide that targets soilborne Pythium spp. To go along with this outbreak, numerous instances of Pythium root rot on seedling corn from April flooded fields have been diagnosed in the MU Plant Disease Clinic.
Max Gilley recently joined the Mizzou Turfgrass Pathology team as a Ph.D. student. He will be taking over the research project on soilborne Pythium spp., which was established through the Environmental Institute for Golf/GCSAA Chapter Cooperative Program along with funds pledged from the Heart of America, Ozark Turfgrass Association, and Wisconsin GCSAA Chapters. Max completed his M.S. degree in plant pathology at Mississippi State under the direction of Dr. Maria Tomaso-Peterson. While there, he worked on characterizing diseases of Giant Miscanthus, a bioenergy crop.
As a refresher, the project objectives are to define the distribution of Pythium species throughout the Midwest and provide management guidelines for Pythium root diseases occurring in the region. There are two distinct soilborne Pythium diseases that can occur on creeping bentgrass putting greens. Pythium root rot (PRR) occurs in over-saturated conditions or areas with poor drainage. Symptoms of PRR include red, yellow, or dark-colored areas occurring in irregular, mosaic-like patterns that can occasionally follow drainage patterns. Individual plants may have rotted crowns and roots. For more information regarding PRR see a previous disease update (6/26/2011 update) or disease profile (PRR disease profile). Pythium root dysfunction (PRD) as caused by Pythium volutum is a disease that was recently described in North Carolina on young (<5-7 years) bentgrass putting greens. While PRD has not been observed to our knowledge in Missouri, it is a disease we are on the look out for. Symptoms of PRD include plants that are initially wilted and chlorotic and develop a yellow-to-orange foliar decline in patches. Infected roots are tan and lack root hairs. Unlike PRR, symptoms of PRD are most severe during periods of hot and/or dry weather.
If you suspect a Pythium root disease (root dysfunction/root rot) and would like to submit a sample, please contact me (email@example.com) or Max Gilley (firstname.lastname@example.org) for more information.
Plans are underway for the 2014 Mizzou Turfgrass & Ornamental Field Day! The event will be held July 22nd at our research facility at South Farms. Presentation topics are set to include post-application irrigation impact on fungicide performance, NTEP warm season survival, impact of spring fertilizer technologies on tall fescue lawns, and a litany of others. Save the date and look forward to seeing you there.
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Extension Turfgrass Pathologist
University of Missouri