Microwave Radiometry: A
Pennsylvania Turfgrass Council
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Penn State Turf Team
Growth and Support
As we enter another busy growing season, the PTC family reflects on the challenges and successes of the season past. While changes in Penn State turf faculty presented a short-term hurdle, the commitment of our organization has been integral to the continuation of the Pennsylvania turf research community. We are proud to have donated funds to a number of avenues for research advancement and support of future turfgrass professionals. These investments benefit our members and our industry by training the incoming workforce and discovering new and innovative products and practices.
PTC thanks you for your continued support not only financially, but through your participation in events, training and sharing your collective experiences on the ground. Your support matters, it is through your commitment that our industry continues to grow and thrive!
PA Turfgrass Council Research and Scholarship Fund provided the following support to the Penn State Turf Program in 2024.
$8,000 Support PSU Student travel to attend SFMA and GCSAA Travel
$25,000 PTC Excellence Account through Penn State University to support the PSU Turfgrass Science Program
$55,000 Watson Scholarship Donation for two- and four-year PSU Turfgrass Science students
$25,000 Start-UP funds for Dr. Manoj Chhetri
$50,000 Start-UP funds to support Dr. Chase Straw
$12,000 PTC Scholarships for two- and four-year PSU Turfgrass Science students
$101,000 John Kaminski, Ph.D. Research Account
$216,000 Ben McGraw, Ph.D. Research Account
$42,000 Max Schlossberg, Ph.D Research Account
$127,263 Smithco 300 Gallon GPS Sprayer for Valentine Turf Research Facility and for Teaching in the two- and four-year Turfgrass Science Program (pictured below) •
Jeffrey A. Borger Senior Instructor Emeritus in Turfgrass Weed Management 814-865-3005 • jborger@psu.edu
Michael A. Fidanza, Ph.D. Professor of Plant & Soil Science 610-396-6330 • maf100@psu.edu
David R. Huff, Ph.D. Professor of Turfgrass Genetics 814-863-9805 • drh15@psu.edu
Brad Jakubowski Instructor of Plant Science 814-865-7118 • brj8@psu.edu
John E. Kaminski, Ph.D. Professor of Turfgrass Science 814-865-3007 • jek156@psu.edu
Peter J. Landschoot, Ph.D. Professor of Turfgrass Science 814-863-1017 • pjl1@psu.edu
Ben McGraw, Ph.D. Associate Professor of Turfgrass Entomology 814-865-1138 • bam53@psu.edu
Andrew S. McNitt, Ph.D. Professor Emeritus of Soil Science 814-863-1368 • asm4@psu.edu
Max Schlossberg, Ph.D. Associate Professor of Turfgrass Nutrition / Soil Fertility 814-863-1015 • mjs38@psu.edu
Al J. Turgeon, Ph.D. Professor Emeritus of Turfgrass Management aturgeon@psu.edu
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Fidanza Receives Grau Award
TheFred V. Grau Turfgrass Science Award is administered by the Crop Science Society of America. This award is presented in recognition of significant career contributions in turfgrass science during the most recent 15 years.
Evaluation Criteria
1. Significance and originality of basic and/or applied research
2. Teaching ability and effectiveness
3. Planning and implementation of extension programs
4. Development and implementation of significant industrial programs
5. Administrative ability and effectiveness
6. Total impact of contributions on turfgrass science, nationally and internationally
Dr. Fidanza is the 2024 recipient, and is a professor of plant and soil science at Penn State Berks, in Reading, PA.
1987 James R. Watson*
1988 James B. Beard
1989 Jack J. Murray
1990 C. Reed Funk
1991 Glen W. Burton
1992 Robert C. Shearman
1993 Donald V. Waddington*
1994 William A. Meyer
1995 B.J. Johnson
1996 Terrance P. Riordan
1997 Keith J. Karnok
1998 A.J. Powell, Jr.
1999 Nick E. Christians
2000 Richard E. Schmidt*
2001 Wayne W. Hanna
2002 Alfred J. Turgeon*
2003 Paul E. Rieke
2004 T. Karl Danneberger
2005 A. Douglas Brede
2006 Arden A. Baltensperger
2007 Peter H. Dernoeden
2008 Roch E. Gaussoin
2009 Thomas L. Watschke*
2010 Milton C. Engelke
2011 Jack D. Fry
2012 Leah A. Brilman
2013 No Award
2014 Lambert B. McCarty
2015 Michael D. Richardson
2016 Bruce B. Clarke
2017 S. Bruce Martin
2018 Kevin N. Morris
2019 James A. Murphy
2020 John Clinton Stier
2021 Elizabeth A. Guertal
2022 Grady L. Miller
2023 Bernhard Leinauer
2024 Michael A. Fidanza*
* Graduate student and/or faculty member of Penn State.
The Fred V. Grau Turfgrass Science Award
Originally Written By Peter H. Dernoeden (Source: http://archive.lib.msu.edu/tic/monos/171620.pdf)
The“Turfgrass Science Award” was first awarded in 1987 by the C-5 Division of the Crop Science Society of America (CSSA) and was named in honor of Dr. Fred V. Grau. Donald V. Waddington was Chair of C-5 at the time the award was presented and accepted by CSSA in 1986. The award was proposed by John F. Shoulders and John R. Watson (C-5 “Award and Professional Advancement Committee”) during the 1985 business meeting of the C-5 Division (Robert N. Carrow presiding). The committee recommended that the new award be named the Fred V. Grau Award and that it be established to recognize significant career accomplishments to Turfgrass Science. The proposed award was brought forward by the C-5 Chair (D.V. Waddington) to CSSA in 1986 (James B. Beard presiding CSSA President). At the time the executive committee of CSSA had a policy that awards not be named for an individual or company. Furthermore, J. Beard wanted to establish additional awards specific to those members not eligible for existing CSSA awards. Hence, J. Beard initiated contacts with the Seed Science and Turfgrass Science divisions concerning the possibility for these subject related areas to also develop awards. The CSSA Board changed the policy at the 1986 meeting so that names of individuals could be used for memorial or honorary awards. A major criterion for the Fred V. Grau Award stipulated that candidates be evaluated on their most recent 15 years of activity to ensure persons with a sustained record of achievement would be awarded. An honorarium was established and funds for the award were solicited by D.V. Waddington from state and regional turfgrass councils, associations and similar organizations.
Dr. Grau was born and raised on a farm in Jefferson, Douglas County, Nebraska and graduated from the Nebraska State College (now the University of Nebraska - Lincoln) in 1931. Dr. Franklin D. Keim, a professor at UNL who taught turfgrass culture and inspired a number of students to enter the field, received a $300.00 grant from the United States Golf Association (USGA) to evaluate the effects of various fertilizers on turf. Fred Grau was hired to care for the plots and maintain the records. This experience, as well as a greenkeeping job he had to earn money to pay for college, were the stepping stones to his turfgrass career. After graduation from UNL, he was hired by Dr. John Monteith, Jr., Director of the USGA Green Section, to care for the turf research plots at the Arlington Turf Gardens, now the site of the Pentagon. During that time the USGA Green Section had a research relationship with the United States Department of Agriculture (USDA). The USGA and USDA agreed to formally collaborate in 1920. The purpose was to conduct scientific research to improve turf for golf courses. The relationship ended around 1956.
For reasons that are not recorded, but obviously related to a desire to further his career, Grau enrolled at the University of Maryland (Maryland Agricultural College prior to 1926) to pursue an advanced degree. His Master of Science (1933) thesis was titled “The Use of Chemicals in the Control of Turf Weeds.” He initiated his research with about 20 chemicals and evaluated them in the greenhouse and on lawns around the University of Maryland campus. Once he narrowed down the list of candidate herbicides he conducted studies at the Bannockburn Golf Course in Glen Echo, MD; East Potomac Golf Course in DC and the Arlington Turf Gardens in VA.
Most of his studies were conducted on Kentucky bluegrass, the predominating species in the DC area at that time. Some studies were performed in mixed German bent, colonial bentgrass and bermudagrass. He remained an employee of the Green Section at this time and was supervised by Dr. John Monteith, Jr. of the USGA and Professor Jacob Metzger at the University of Maryland. He stated in his MS thesis that the five most important weeds of putting greens included crabgrass, chickweeds, dandelion, plantains and white clover. He estimated that weed control in greens, which was performed by handpicking, cost about $1000 annually and this figure would include weeding areas immediately surrounding the clubhouse. He reported that “plantains, chickweeds, white clover, pennywort and knotweed have succumbed to the soluble compounds of arsenic.” “Of the chemicals used sodium chlorate has most effectively controlled crabgrass and milk purslane.” He found in his weed control experiments that live steam and dry heat from an asphalt heater were “nonselective and impracticable.” Sodium chlorate caused slight turf injury and he estimated that the material would cost about ten dollars an acre. Although there is no mention of grubs in his thesis, he did say at a later time that he found that lead arsenate was effective in controlling crabgrass and grubs and noted that the plots were still free of crabgrass and grubs when the bulldozers arrived to build the Pentagon in 1942 (GCM, January 1985). Due to the immense financial hardship of the depression, the Green Section eliminated many jobs, including his. Professor Jacob Metzger, Chair of the Department of Agronomy at the University of Maryland “rescued him” by finding funds for him to conduct a survey of Maryland pastures. His dissertation was titled “Factors Affecting Pasture Quality – An Inventory of Soils, Vegetation, and Management of Maryland Permanent Pastures.” He received his Ph.D. in 1935 and was hired in the same year to be the first Extension Turfgrass Specialist at the Pennsylvania State College (now Pennsylvania State University). The position was evenly split between turf and forages. As an Extension Agronomist, he traveled throughout Pennsylvania. It was on one of these Extension trips in Berks County in 1935 that he discovered what was to become known as ‘Penngift’ crownvetch. In 1953, Penngift was formally released by Dr. Grau and Professor Musser at Penn State and in 1987 it was named the “Beautification and Conservation Plant” by the State of Pennsylvania. Today, Penngift can be found growing along thousands of miles of Pennsylvania and Maryland highways, stabilizing soil while providing the beauty of it purple summer flowers. During World War II, Dr. Grau entered the Air Force, where he helped establish grass airfields under the guidance of Professor Musser, who also was working with the Air Force at this time. In 1945, he was hired to be Director of the USGA Green Section in Beltsville, MD and moved to College Park.
During Dr. Grau’s tenure as Director of the Green Section (1945 to 1953), the American Society of Agronomy (ASA) recognized turf as a legitimate agricultural entity and established the C-5 Division after an aggressive letter writing campaign that he initiated (ASA’s Crop Section became CSSA in 1955). Dr. Grau served as the first C-5 Chair and chaired a separate ASA Turfgrass Committee from 1946 to 1955, which served as a clearinghouse for turfgrass research information. The recognition provided by a Turfgrass Division in ASA gave agricultural experiment stations (state and federally funded research units at land grant institutions)
the impetus to establish turfgrass-oriented research and educational programs within agricultural universities. This led to a rapid increase in the number turfgrass science programs at American universities. It also was during this period when he played an important role in the release of ‘Merion’ Kentucky bluegrass, ‘Meyer’ zoysiagrass, and U-3 bermudagrass. He left the USGA in February 1953 and became a consultant to golf courses and several business including West Point Products (producers of aerifiers and other turf machinery) and Hercules Powder Company (Nitroform fertilizer, including Power Blue and Blue Chip). He also operated Grasslyn, the family business for growing Penngift crownvetch. Dr. Grau was a founding member of the Pennsylvania Turfgrass Council in 1955 and served as Executive Director from 1968 to 1975 and Executive Secretary from 1976 to 1981. Dr. Grau also was a founding member of the Musser International Turfgrass Foundation in 1969, serving as President for 20 years. Among his many awards were the USGA Green Section Award (1969) and the GCSAA Distinguished Service Award (1954 and 1975). He died in 1990 at the age of 88. His legacy was summarized by Mr. Tom Mascaro (GCM. January 1991), who stated, “He has left us in body but not spirit. He will continue to be with us in our lives, and in the lives of future generations. He was a man of vision – and a man of our future.”
References and Acknowledgements
Information provided by Mr. Jim Snow, Director of the USGA Green Section; Dr. Don Waddington, Professor Emeritus, Penn State University; and Dr. James B. Beard, Professor Emeritus, Texas A&M University is gratefully acknowledged. Most of the information in this story was obtained from articles and letters written by Dr. Grau and published in Golf Course Superintendent (September/October 1976); Golf Course Management (January 1985); and from “…And A Remembrance” written by Mr. Tom Mascaro (Golf Course Management, January 1991). •
Better Built. Quality Results.
Dr. Fred V. Grau
G GPGCSA Presents 2024 Distinguished Service Award
reater Pittsburgh Golf Course Superintendents Association presented its annual Distinguished Service/ Chris Morup Award at the annual meeting at Sewickley Heights Golf Club on October 8, 2024. During the meeting, Bob Capranica, Irrigation Sales Manager for E.H. Griffith, Inc. was presented the 2024 Distinguished Service Award. This award acknowledges the effort that Bob put into his profession and speaks highly of how well Bob is perceived in the industry. Bob has been an invaluable member of the Greater Pittsburgh Golf Course Superintendents Association for over 40 years, and his contributions to the field are nothing short of extraordinary.
Bob’s work ethic is unparalleled, and his dedication to customer service is truly remarkable. His mission has always been to professionally serve our customers, offering them the best possible solutions for their irrigation needs. This unwavering commitment has not only earned him respect within the industry but has also resulted in him receiving multiple Toro sales and service awards,
including the prestigious Toro Irrigation Master Salesperson Award. These accolades are a testament to Bob’s significant impact and his exceptional dedication to his work.
Beyond his professional achievements, Bob Capranica is one of the most genuine and sincere individuals you will ever meet. His integrity and passion for his work make him a deserving candidate for this honor. Bob’s contributions have left a lasting imprint on our industry, and he continues to be a beacon of excellence and professionalism.
The GPGCSA DSA
This award was first presented in 1992 to Chris Morup. Chris graduated from the Penn State Turf Program and during the years 1968-1988 was Superintendent of golf courses in Pittsburgh, Cleveland, and Philadelphia. In November of 1991, Chris broke his neck when a large branch from a tree he was taking down fell the wrong way. He spent the last nine years of his life paralyzed from the neck down and dependent on a respirator. He died at home on September 18, 2000. His incredible faith and his positive, optimistic attitude were an inspiration to all his family and friends. Chris also played an instrumental role in the merging of the two previous Superintendent’s Associations and forming the Greater Pittsburgh GCSA in 1983. This award was created to honor Chris for the person in the Pittsburgh area best exemplifying integrity in the turfgrass profession and/or notable personal achievements for the GPGCSA membership. •
A New Tool for Precision Irrigation on Golf Courses Microwave Radiometry
As
By Madan Sapkota, Chase M. Straw, Weston W. Floyd, and Elia Scudiero
global demand for freshwater intensifies and the environmental impact of water use becomes more apparent, golf course superintendents face increasing pressure to manage water resources more efficiently. Conventional irrigation scheduling methods may result in overwatering or underwatering, leading to water waste and negatively affecting turfgrass health and playability. Precision irrigation has emerged as an advanced approach that applies water precisely where and when it is needed, using technologies that monitor soil moisture and optimize irrigation practices.
Accurate soil moisture data are crucial for precision irrigation, as they provide real-time information necessary for refining irrigation schedules, minimizing water waste, and maintaining healthy turfgrass. However, current sensor technologies face challenges in covering large areas like golf course fairways. While traditional methods, such as gravimetric techniques, are accurate, they are also labor-intensive and impractical for large-scale use. Time domain reflectometry (TDR) sensors, commonly used by superintendents in the United States, provide real-time data with less labor but are limited to point-specific measurements, making them less efficient for extensive areas. To overcome these limitations, new solutions are needed to improve the accuracy and reliability of soil moisture measurements over large areas, ultimately enhancing water conservation and promoting healthier turfgrass.
Introducing Microwave Radiometry
To address the limitations of current soil moisture sensing technologies, microwave sensing emerges as a promising solution for large-scale, accurate soil moisture measurement on golf courses. Microwave sensing can be categorized into active and passive methods. Active microwave sensing, such as synthetic aperture radar (SAR), involves emitting microwave signals to the ground and measuring the reflected signals. This method is effective for mapping surface features but can be complex and resourceintensive. In contrast, passive microwave sensing, or microwave radiometry, measures the natural microwave emissions from the surface. This passive approach is particularly effective for assessing soil moisture content, as it directly responds to the water present in the soil.
Microwave Radiometry in Golf Course Management
Microwave radiometry is emerging as a promising technology for soil moisture measurement, with significant potential for largescale applications in golf course management. An example of this technology is the Portable L-Band Radiometer (PoLRa), commercially known as turfRad (TerraRad Tech AG, Zurich, Switzerland). Although PoLRa represents a new tool for golf course superintendents, the principles of microwave radiometry could transform how soil moisture is monitored and how high-resolution soil moisture maps are created.
Figure 1. a) Portable L-band Radiometer (PoLRa, i.e., turfRad) sensor mounted on a fairway mower at the golf course.
b) Time domain reflectometry (TDR) measurements (ground truth data) from the data collection conducted on August 14, 2023.
AB
Microwave radiometry detects natural microwave emissions from the surface, allowing for soil moisture measurement up to four inches below the surface. This non-invasive method enables rapid data collection over large areas, making it ideal for managing extensive golf course fairways, where traditional soil moisture-sensing methods are often labor-intensive or limited. The radiometer sensor can be mounted on a mower or strapped to the bed of a utility vehicle, measuring soil moisture about 14 times per second while traveling up to 10 mph. Sensors can also be arranged in an array for broader coverage.
Although microwave radiometry is still relatively new and has not undergone extensive testing in golf course management, it has already been implemented at several golf courses in the United States. Technologies like PoLRa show promise but are still in the early stages of exploration. For precision irrigation, any geospatial sensor technology, including PoLRa, must be rigorously evaluated by assessing soil moisture measurement accuracy and improving soil moisture mapping.
The preliminary research discussed in the next section focuses on the first step: enhancing measurement accuracy through calibration techniques. Calibration involves adjusting the sensor readings to match those from reliable reference measurements, such as those obtained from TDR sensors, to ensure the data collected are accurate and reliable. Factors influencing accuracy include soil moisture content, leaf water levels, brightness temperature (how much microwave radiation is reflected back to the sensor),
temperature fluctuations, and surface roughness (how smooth or uneven the surface is, affecting the scattering of microwave signals). Different turfgrass species may also affect readings due to variations in leaf water content and surface characteristics. Therefore, site-specific calibrations are essential for ensuring reliable measurements. Significant effort is needed to develop and apply effective calibration techniques to achieve precise and dependable results.
Preliminary Research at Champions Golf Club, Houston, Texas
On August 14, 2023, Texas A&M University researchers conducted a study at Champions Golf Club (Jackrabbit Course) in Houston, Texas, focusing on fairways 2, 6, and 13, which feature ‘Tifway 419’ hybrid bermudagrass in sandy loam soil. Two methods to measure soil moisture were used: the PoLRa (turfRad) microwave radiometer and handheld TDR 350 sensors (FieldScout TDR 350 Soil Moisture Meter, Spectrum Technologies, Inc., Plainfield, IL, USA). The PoLRa was mounted on a fairway mower about one meter above the ground (Figure 1a) and driven at speeds of 3.54.5 mph. The mower made three passes per fairway—two near the edges and one down the center—while data were collected at twelve randomly chosen points per fairway. After each pass, the points were flagged and exact times were recorded using the ‘Unix Time’ app.
Previous research has shown strong correlations between TDR and gravimetric soil moisture measurements, especially in coarse, non-conductive soils. Since TDR is practical for golf course superintendents, it provides reliable data for calibrating the PoLRa sensor. After using PoLRa to take measurements, soil moisture readings were collected at marked points using handheld TDR sensors at depths of 1.5, 3.0, and 4.8 inches (Figure 1b). The PoLRa data were then matched with the TDR readings based on the recorded times to ensure accurate comparisons.
For calibration, we used ANCOVA regression, a statistical method that helps understand the relationship between different variables while controlling for other factors. In this method, TDR readings were treated as the dependent variable (the outcome we are measuring), and the brightness temperature from PoLRa’s vertical polarization was the independent variable (the factor we are testing to see its effect). This method enabled more accurate estimation of soil moisture levels. We assessed
the model’s performance using metrics such as R², which indicates how well the model explains the variation in soil moisture, and mean absolute error (MAE), which shows the average size of the prediction errors.
Our initial calibration using PoLRa’s off-the-shelf (i.e., factory) settings showed an R² value of 0.60 (P < 0.01) and MAE of 0.06 (Figure 2a), indicating that 60% of the variability in soil moisture readings could be explained by PoLRa data. While promising, these results highlighted the need for further refinement to improve accuracy. Using an advanced ANCOVA calibration approach that incorporated additional factors such as brightness temperature, the model’s performance significantly improved. The R² value increased to 0.78 (P < 0.01) (Figure 2b), explaining 78% of the variability in soil moisture, and the MAE was reduced to 0.03. These results demonstrate the effectiveness of advanced calibration techniques in enhancing the accuracy of PoLRa’s soil moisture measurements.
Figure 2. a) The relationship between off-the-shelf PoLRa (turfRad) volumetric water content (VWC) and ground truth time domain reflectometry (TDR) measurements from three golf course fairways during a survey at Champions Golf Club (Jackrabbit Course) in Houston, Texas.
b) A comparison of observed vs. estimated VWC using the ANCOVA regression approach.
Future Direction for Accuracy and Reliability
The improved soil moisture measurement accuracy from using ANCOVA to calibrate microwave radiometry technology highlights its potential to improve golf course irrigation. While effective, ANCOVA requires further refinement. Future research should explore additional factors, such as different soil types, turfgrass species and varieties, management practices, and various climatic environments. Considering temporal factors, including seasonal variations, will also help enhance the model’s year-round accuracy.
Fine-Tuning Microwave Radiometry and Improving Soil Moisture Mapping
After improving soil moisture measurement accuracy, the next step in optimizing precision irrigation is enhancing soil moisture mapping across large areas like fairways. These maps help visualize soil moisture variability, as shown in Figure 3, and hold great potential for precision irrigation. By integrating PoLRa, which utilizes both microwave radiometry and GPS for georeferencing soil moisture data, with digital job board technology, real-time georeferencing of soil moisture readings can be achieved as a PoLRa moves across fairways. The resulting maps can reveal patterns of soil moisture variability, which can be more effectively addressed once the soil moisture calibrations are fully applied (Figure 3a and 3b).
Conclusions
Microwave radiometry holds potential to transform precision irrigation on golf courses. Its ability to provide accurate, large-scale soil moisture measurements could revolutionize water management for superintendents. By overcoming the limitations of current sensors and offering a non-invasive, efficient method for real-time data collection, microwave radiometry
Figure 3. a) Soil moisture maps generated by integrating PoLRa (turfRad) data with digital job board (ASB taskTracker) for fairway 2 and 6 (a and b, respectively) at Champions Golf Club (Jackrabbit Course) in Houston, Texas, during a survey on August 14, 2023.
could become essential in modern golf course management. Although further research is needed to improve accuracy and reliability, the final step to ease the implementation of precision irrigation is integrating this technology with irrigation systems. This integration could reduce the need for manual adjustments of irrigation schedules by allowing the system to recommend adjustments based on soil moisture and possibly other turfgrass or soil data. Superintendents would then be able to simply approve or adjust these recommendations as needed. This approach could ultimately lead to more sustainable water use, improved turfgrass health, and enhanced overall golf course quality. •
M. Sapkota, C.M. Straw, and W.W. Floyd,
Department of Soil and Crop Sciences
Texas A&M University 3100 F and B Rd College Station, TX 77845
E. Scudiero
University of California Riverside West Big Spring Rd Riverside, CA 92507
Acknowledgement
The authors gratefully acknowledge Chris Ortmeier, Director of Agronomy at Champions Golf Club, and Cliff Morris, Superintendent of the Jackrabbit Course, for providing space for our research. We are also thankful to the United States Golf Association and the South Texas Golf Course Superintendents Association for their financial support. Special thanks to Dr. Derek Houtz, Founder and CEO of TerraRad Tech AG, for his technical support with the PoLRa sensor.
TURFGRASS DISEASES
Summer patch
(Causal fungus: Magnaporthiopsis poae)
By Pete Landschoot, Ph.D.
Summer patch, sometimes called Poa patch, is a root and crown disease of golf course turf, home lawns, grounds, and athletic fields.
This hot-weather disease is caused by the fungus Magnaporthiopsis poae and occurs on annual bluegrass, Kentucky bluegrass, and fine fescues. Creeping bentgrass, perennial ryegrass, and tall fescue are highly resistant to summer patch.
Symptoms and Signs
On annual bluegrass putting greens, tees, and fairways, summer patch may begin as small (<4-inch diameter) circular patches that progress to larger (4 to 18-inch diameter) patches as the disease worsens. Large patches will often appear suddenly with no indication of previous disease activity. In severe cases, patches may coalesce and destroy large areas of turf. Summer patch-diseased annual bluegrass initially takes on a yellow color, then becomes brown as affected plants die. On greens, tees, and fairways with mixed annual bluegrass/creeping bentgrass populations, creeping bentgrass will often colonize the center of diseased patches of annual bluegrass.
Symptoms of summer patch in lawns, grounds, and athletic fields typically begin as circular areas of wilting Kentucky bluegrass or fine fescue turf, progressing to reddish-brown or light brown sunken patches, often with a tuft of healthy grass in patch centers. Patches range from a few inches to over three feet in diameter and can appear as a mix of rings, crescents, or spots of various sizes. In severe cases, patches of diseased turf can coalesce, making field diagnosis difficult.
Figure 1. Summer patch symptoms on an annual bluegrass putting green (left) and a patch of diseased annual bluegrass being colonized by resistant creeping bentgrass. Photos: Peter Landschoot, Penn State
Summer patch. Photo: Peter Landschoot, Penn State
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Summer patch symptoms can mimic those of other diseases or turf injury resulting from summer heat stress or drought conditions. Hence, diseased turf should be examined by a qualified diagnostician using a microscope if positive identification is necessary. A microscope examination of summer patch affected plants typically reveals brown, rotting crown tissues and discoloration of the vascular cylinder of roots. Dark brown strands of fungal hyphae (ectotrophic runner hyphae) on the surface of rotting roots, and brown fungal cells inside of root tissues indicate the presence of the summer patch pathogen, M. poae.
Disease Cycle
Dark brown ectotrophic runner hyphae of the causal fungus colonize the surface of turfgrass roots during spring, summer, and fall, but do not typically initiate disease activities until susceptible plants are subjected to summer heat stress conditions. When conditions are favorable for summer patch, the causal fungus penetrates deep into root tissues and invades water and nutrient conducting elements in the vascular cylinder, causing plants to wilt and die. Hyphal strands of M. poae on infected plant debris can be disseminated to other areas via aerator tines, verticutting blades, excavation equipment, or through the movement of soil. Mycelium of M. poae remains dormant during winter in northern climates but can resume growth and disease activities the following summer. This pathogen does not produce spores in the field.
Disease Development
Summer patch usually occurs on susceptible grasses in midsummer during extended periods of high temperatures (> 82°F) following rainy periods. This disease does not appear during the cool weather of spring and fall. On golf courses, summer patch is frequently observed in areas that receive poor air circulation, low mowing heights, heavy traffic, excessive irrigation, and inadequate drainage. In lawns and sports turf, summer patch is often found in pure stands of Kentucky bluegrass or fine fescue turf with wet or dry soils, and in areas subjected to low mowing heights and soil compaction.
Figure 3. A severe case of summer patch in a fine fescue lawn where patches have coalesced to destroy a large area of turf. Photo: Peter Landschoot, Penn State
Figure 4. Dark brown, rotting roots and stem base (left) and vascular root discoloration with ectotrophic runner hyphae of M. poae (right) on summer patch-affected annual bluegrass.
Photos: Peter Landschoot, Penn State
Figure 2. Summer patch symptoms on a lawn in central Pennsylvania. Photos: Peter Landschoot, Penn State
Cultural Control
Because summer patch is a root disease, cultural practices that promote good root growth will aid in reducing disease severity. Increased aeration and improved drainage on compacted and poorly drained soils will alleviate some root inhibition and enable turf to better resist infection by M. poae. Low mowing heights are associated with shallow rooting; thus, raising the height of cut may result in less summer patch injury. In some cases, fertilizing with an acidifying fertilizer, such as ammonium sulfate, during spring and fall to lower soil pH may help reduce the severity of future summer patch outbreaks. On golf course turf with persistent summer patch problems, encouraging the growth of creeping bentgrass will reduce summer patch problems. In lawns and sports turf, overseeding turf with a history of summer patch with perennial ryegrass or tall fescue will reduce or eliminate symptom expression.
Chemical Control
On golf courses, summer patch can be controlled with penetrant fungicides, provided applications are made on a preventative basis (three to four weeks prior to symptom development) and high labelrecommended rates are used. On Pennsylvania golf courses with a history of summer patch on greens, the first summer patch application is usually made between late April and mid-May, with follow-up applications every three to four weeks until August. Fungicides should be applied with large spray volumes (up to five gallons of water per 1000 sq ft) to ensure significant concentrations of active ingredient reach turfgrass crowns and the upper portion of root systems. An alternative to using large spray volumes is to apply the fungicide in the early morning, then lightly irrigate the treated area immediately with enough water to wash spray droplets off the leaf canopy and into the turf/soil surface where crowns and roots are located. Penetrant fungicides in the demethylation inhibitor (DMI), quinone outside inhibitor (QoI), and methyl benzimidazole carbamate (MBC) classes tend to provide the best control of summer patch.
High rates of certain DMI fungicides can produce growth-regulating effects and some phytotoxicity on putting green turf during high-temperature periods in summer; thus, these products are better used for preventative treatments in spring. Preventative fungicide programs for summer patch control are often too expensive for lawns and low-budget athletic fields and may not provide complete control. Turf managers should be aware that “curative” or post symptom fungicide applications generally result in marginal or poor control. •
Table 1. Some penetrant fungicides labeled for control of summer patch disease.
Active ingredient according to class Fungicide class, FRAC code*, and plant mobility classification** Product name(s)***
Demethylation inhibitors (DMI)
flutriafol
DMI, 3, acropetal penetrant Rayora mefentrifluconazole DMI, 3, acropetal penetrant Maxtima metconazole DMI, 3, acropetal penetrant Tourney myclobutanil DMI, 3, acropetal penetrant
Andersons Golden Eagle DG, Eagle 20EW, Myclobutanil 20EW
propiconazole
DMI, 3, acropetal penetrant Andersons Prophesy DG, Banner Maxx II, Dorado, Lesco Spectator, Propiconazole 14.3, Savvi prothioconazole
DMI, 3, acropetal penetrant Densicor
tebuconazole
ArmorTech TEB 360 XL, Mirage Stressgard, Sipcam Clearscape ETQ, Tebuconazole 3.6, Torque triadimefon
DMI, 3, acropetal penetrant
DMI, 3, acropetal penetrant Andersons Fungicide VII, Bayleton FLO triticonazole
Methyl benzimidazole carbamates (MBC)
thiophanate-methyl
Phenylpyrroles (PP)
fludioxonil
Quinone outside inhibitors (QoI)
azoxystrobin
DMI, 3, acropetal penetrant Trinity
MBC, 1, acropetal penetrant
3336 EG, 3336 DG, Cavalier F, Fungo Flo, Lesco T-Storm, SysTec 1998, TM 4.5, TM 85 WDG, T-Methyl, Transom 4.5F
Signal transduction, 12, local penetrant Medallion
QoI, 11, acropetal penetrant Heritage, Heritage TL, Strobe 50WG, Strobe 2L, Strobe Pro fluoxastrobin
QoI, 11, acropetal penetrant Disarm G, Disarm 480 SC, Fame Granular, Fame SC pyraclostrobin
QoI, 11, local penetrant Insignia Intrinsic (suppression only) trifloxystrobin
QoI, 11, local penetrant Compass azoxystrobin + propiconazole
azoxystrobin + propiconazole + pydiflumetofen
azoxystrobin + tebuconazole
benzovindiflupyr + difenoconazole
QoI, 11, acropetal penetrant + DMI, 3, acropetal penetrant Goliath XP, Headway, Headway G
QoI, 11, acropetal penetrant + DMI, 3, acropetal penetrant + SDHI, 7, acropetal penetrant Posterity XT
QoI, 11, acropetal penetrant + DMI, 3, acropetal penetrant ArmorTech Zoxy-T, Oximus
SDHI, 7, acropetal penetrant + DMI, 3, acropetal penetrant Ascernity boscalid + pyraclostrobin
chlorothalonil + propiconazole
chlorothalonil + iprodione + thiophanate-methyl + tebuconazole
chlorothalonil + tebuconazole
fluoxastrobin + chlorothalonil
fluoxastrobin + myclobutanil
fluoxastrobin + tebuconazole
isofetamid + tebuconazole
mefentrifluconazole + pyraclostrobin
PCNB + tebuconazole
pyraclostrobin + fluxapyroxad
pyraclostrobin + triticonazole
trifloxystrobin + triadimefon
SDHI, 7, acropetal penetrant + QoI, 11, local penetrant Honor Intrinsic
Chloronitrile, M5, contact + DMI, 3, acropetal penetrant Concert II
Chloronitrile, M5, contact + Dicarboximide, 2, local penetrant + MBC, 1, acropetal penetrant + DMI, 3, acropetal penetrant Enclave
Chloronitrile, M5, contact + DMI, 3, acropetal penetrant E-Scape ETQ
QoI, 11, acropetal penetrant + Chloronitrile, M5, contact Disarm C, Fame+C
QoI, 11, acropetal penetrant + DMI, 3, acropetal penetrant Disarm M
QoI, 11, acropetal penetrant + DMI, 3, acropetal penetrant Fame+T
SDHI, 7, acropetal penetrant + DMI, 3, acropetal penetrant Tekken
DMI, 3, acropetal penetrant + QoI, 11, local penetrant Navicon
Aromatic hydrocarbon, 14, contact + DMI, 3, acropetal penetrant Premion
QoI, 11, local penetrant + SDHI, 7, acropetal penetrant Lexicon Intrinsic
QoI, 11, local penetrant + DMI, 3, acropetal penetrant Pillar G
QoI, 11, acropetal penetrant + DMI, 3, acropetal penetrant Armada 50WG, Tartan Stressgard
Table 2. Some combination product fungicides labeled for control of summer patch disease.
Active ingredient
azoxystrobin + acibenzolar-S-methyl
Fungicide class, FRAC code*, and plant mobility classification** Product name(s)***
QoI, 11, acropetal penetrant + Host defense induction, P1, systemic penetrant Heritage Action azoxystrobin + difenoconazole
QoI, 11, acropetal penetrant + DMI, 3, acropetal penetrant Briskway
*FRAC is an abbreviation for Fungicide Resistance Action Committee. The FRAC code/resistance group system consists of numbers indicating classes or groups of fungicides based on mode of action, and letters that refer to broad classifications of fungicides (P = host plant defense inducers; M = multi-site fungicides; and U = unknown mode of action and unknown resistance risk). Due to the risk of fungicide resistance, turf managers should avoid excessive use of fungicides within the same FRAC code/resistance group and alternate products among different FRAC codes/ resistance groups.
**Plant mobility classification refers to a fungicide’s ability to penetrate plant surfaces or remain on plant leaf or stem surfaces without penetration. Fungicides that penetrate plant surfaces and are translocated mostly upwards through plant xylem tissues are called acropetal penetrants (acropetal = toward the apex). Fungicides that enter plant cuticles or move limited distances in internal plant spaces, but do not translocate through vascular tissues (xylem and/or phloem) are called local penetrants. Contact fungicides do not penetrate plant surfaces and only inhibit fungal pathogens residing on leaf and stem surfaces.
***Follow label precautionary statements, restrictions, and directions regarding tolerant turfgrass species, rates, and timing of applications.
References
Buhler, W. Fungicide spraying by the numbers.
Clarke, B.B., P. Koch, and G. Munshaw. 2020. Chemical control of turfgrass diseases 2020. University of Kentucky, Rutgers University, and University of Wisconsin.
Latin, R. 2011. A practical guide to turfgrass fungicides. American Phytopathological Society Press, St. Paul, MN.
Smiley, R.W., P.H. Dernoeden, and B.B. Clarke. 2005. Compendium of turfgrass diseases, 3rd Edition. American Phytopathological Society Press, St. Paul, MN.
Smith, J. D., N. Jackson, and A.R. Woolhouse. 1989. Fungal diseases of amenity turfgrasses. 3rd ed. E. and F. Spon, London.
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