Pythium patch is a relatively new disease of annual bluegrass putting greens. The disease was first observed on a golf course in 2005, but only recently was the pathogen confirmed.
Case Study
The story began in 2005, when Dr. Kaminski first stumbled upon the enigmatic Pythium patch on a golf course in Connecticut. The disease’s resemblance to summer patch initially created an air of uncertainty, compounded by the fact that numerous labs misdiagnosed its true nature. However, this initial challenge served as a catalyst for deeper investigation.
Amidst the diagnostic intricacies, Dr. Kaminski’s discerning eye detected a unique thread that would ultimately unravel the mystery. He discerned a distinctive foliar Pythium variant intertwined with the disease, a variant that exclusively targeted annual bluegrass on mixed stands alongside bentgrass. With diligent exploration, the puzzle pieces started to align, and the pathogen’s identity came into focus.
Armed with newfound clarity, Dr. Kaminski embarked on a mission to share his discoveries and insights. His journey took him across the New England region, where he engaged with superintendents grappling with turfgrass challenges. As he shared his observations and recommendations, these turfgrass stewards began adjusting their spray programs to incorporate traditional Pythium-targeting products. As a result, the disease’s impact gradually waned.
However, the narrative did not conclude there. The years 2016 and 2017 witnessed a resurgence of Pythium patch, this time making its presence felt on a larger canvas across the northeastern and mid-Atlantic regions of the United States. Dr. Kaminski’s lab embarked on a rigorous research endeavor, deploying their expertise to unravel the mysteries that the pathogen, later identified as Pythium arrhenomanes, held.
With unyielding dedication, the research journey extended nearly two decades, underlining the complexity inherent in unearthing new diseases. Through trials, observations, and collaboration, the pieces of the Pythium patch puzzle were finally assembled. Dr. Kaminski’s lab emerged victorious, confirming the identity of the pathogen that had perplexed turfgrass professionals for years.
This tale serves as a testament to the tenacity and determination required to identify and comprehend novel turfgrass diseases. Dr. Kaminski’s journey, from the initial Connecticut discovery to the comprehensive understanding of Pythium arrhenomanes, stands as an inspiration to budding turfgrass scientists, emphasizing the significance of patience, persistence, and the ceaseless pursuit of knowledge.
Causal agents
Pythium arrhenomanes
Primary Hosts
Annual bluegrass (Poa annua) putting greens and sometimes collars and approaches
Disease Cycle
The pathogen is believed to survive the winter as mycelium or oospores on previously colonized plant material within the soil. Infection is believed to occur from mycelium when temperatures are between 25 and 30oC (77 to 95oF). The pathogen selectively affects annual bluegrass (Poa annua) in mixed populations on bentgrass putting greens. The pathogen appears to spread via mycelium, but the role of various other structures, including antheridia, oogonia, and sporangia, is unclear. The disease will continue to cause damage into the autumn as long as conditions are favorable.
Like most Pythium diseases, Pythium patch seems to be more of a problem in soil-based greens or greens that have implemented a heavy topdressing program over native soil with poor drainage.
Epidemiology
The optimal growth temperatures for Pythium arrhenomanes is between 25 and 35°C (77 and 95°F), with little to no growth observed below 20°C (68°F), and a decline in growth seen at 40°C (104°F). The pathogen grows equally well at temperatures from 25 to 35°C, thereby giving it an advantage over annual bluegrass during the summer months. Disease symptoms generally appear around the same time as summer patch, and the two diseases are often confused for one another.
Patches are slow to grow but can enlarge up to 60 cm (24 in) if left untreated. Factors like poor drainage, hot and humid weather, afternoon thunderstorms, and other conditions favoring Pythium favor the disease development.
Symptoms
When active, distinct chlorotic patches range in size from 10 to 60 cm (5 to 24 in) and can have an orange/yellow halo on the periphery of the patches. As the disease progresses, turf may collapse and become necrotic. Field symptoms resemble summer patch caused by Magnapothiopsis poae. In mixed stands of annual bluegrass and creeping bentgrass, the creeping bentgrass can encroach into affected patches.
Credit: John Kaminski/Penn State University
Signs
Mycelium is not observed in the field, but incubation of symptomatic turfgrass samples reveal coenocytic mycelium on and extending between leaves, oogonium and antheridia, and occasionally oospores embedded in leaf tissue.
Credit: John Kaminski/Penn State University
Management
Little is known about the management of Pythium patch, but the same strategies for dealing with most Pythium diseases is generally recommended.
Cultural
Moisture management is critically important for mitigating this disease. Internal drainage should be installed on older native-soil annual bluegrass putting greens. Pruning trees and installing fans to aid in air movement can also assist in reducing disease symptoms.
Chemical
Fungicidal control is relatively easy with this disease. Preventive control on turfgrass with chronic Pythium patch outbreaks can be suppressed with 14 to 21 day applications of most traditional Pythium fungicides.
For curative control, foliar applications (do not water fungicides in) of propamocarb (Banol), followed 3 to 5 days later by cyazofamid (Segway) will arrest the pathogen.