Recent research reveals new insights into combating this destructive turfgrass disease
Imagine waking up one spring morning to find your once-lush, green lawn now dotted with unsightly brown patches that seem to grow larger each day.
This isn't a case of poor maintenance or accidental chemical spillage—it's likely large patch disease, a formidable fungal adversary that plagues warm-season turfgrasses across the southern United States and beyond. Recent groundbreaking research from the University of Arkansas has shed new light on this destructive phenomenon, offering both explanation and hope for homeowners and turf professionals alike 3 .
Large patch disease represents a significant challenge to the aesthetics, functionality, and health of turfgrass in lawns, golf courses, and sports fields. The pathogen responsible exploits vulnerable periods in the grass's growth cycle, creating those characteristic expanding rings of damaged turf that can sometimes reach several feet in diameter. Understanding this disease isn't just about maintaining picture-perfect lawns; it's about comprehending a complex biological interaction between fungus, plant, and environment that has economic and ecological implications for communities throughout the region 3 .
Large patch causes significant financial losses in turf management industries annually.
Primarily affects warm-season turfgrasses in southern U.S. states but is expanding its range.
Most active during spring and fall when temperatures range between 50°F and 70°F.
At its core, large patch disease is a fungal infection that primarily targets warm-season turfgrass varieties like bermudagrass and zoysiagrass 3 . These grass species, known for their resilience in warmer climates, enter dormancy during cooler months—a survival strategy that ironically becomes their vulnerability when spring arrives. As temperatures moderate and spring rains begin, the grass begins to emerge from dormancy, its defenses still lowered, creating the perfect opportunity for fungal invasion.
Think of large patch as an unseen invasion from beneath the soil surface. The pathogen (Rhizoctonia solani, in a specialized form known as AG-II-2 LP) survives in soil and infected plant debris during unfavorable conditions, waiting for the precise environmental triggers to launch its attack. When the right combination of moisture and temperature occurs, the fungal network springs to life, attacking the grass's crown tissues and roots, disrupting the flow of water and nutrients .
The progression of symptoms follows a distinct pattern that helps distinguish large patch from other turfgrass problems:
Small, circular patches of discolored grass emerge, typically 6-12 inches in diameter, displaying colors ranging from yellow to orange 3 .
These patches expand outward, sometimes developing a characteristic "frog-eye" appearance with healthier grass in the center.
Patches can coalesce into massive areas of dead and dying grass, sometimes reaching several feet in diameter .
As the infection progresses and grass dies, the color deepens to a distinctive brown that stands in stark contrast to healthy green turf 3 .
Unlike drought stress, which typically creates uniform patterns, large patch creates these distinct circular or arc-shaped patches that continue to expand under favorable conditions. The damage isn't merely cosmetic—the fungal attack compromises the structural integrity of the turf, making it unsuitable for sports and recreation and creating entry points for other pathogens and weeds .
Large patch follows a predictable seasonal pattern that mirrors the growth cycles of its turfgrass hosts. Understanding this cycle is crucial for effective timing of control measures.
| Season | Temperature Range | Disease Activity | Turfgrass Condition |
|---|---|---|---|
| Spring | 50°F–70°F (10°C–21°C) |
|
Emerging from dormancy, vulnerable |
| Summer | Above 80°F (27°C) |
|
Active growth, natural recovery |
| Fall | 50°F–70°F (10°C–21°C) |
|
Preparing for dormancy, vulnerable |
| Winter | Below 50°F (10°C) |
|
Fully dormant, not actively growing |
The disease thrives in the cool, wet conditions of spring and fall when temperatures range between 50°F and 70°F (10°C–21°C) . During these periods, the fungus produces mycelial networks that infect the crown tissues and roots of grass plants. The pathogen disrupts the plant's ability to uptake water and nutrients, leading to the characteristic fading and dieback of grass blades.
As temperatures rise with the onset of summer, the turfgrass often outgrows the disease, and symptoms naturally diminish . This natural recovery highlights the importance of the grass's own vitality in combating the disease—a key insight for management strategies. However, the fungus doesn't disappear; it merely retreats into a dormant state in soil and plant debris, waiting for the return of favorable conditions in the fall.
The fungus becomes active when soil temperatures consistently fall between 50°F and 70°F, making spring and fall the highest risk periods.
To validate and expand upon existing knowledge about large patch disease, Kreinberg conducted controlled field trials in varied Arkansas environments, including Fayetteville and Alma, with a particular focus on zoysiagrass lawns known for their susceptibility to large patch . These experiments were designed to monitor environmental variables, disease progression, and turfgrass response under different management regimes.
The methodology followed a systematic approach:
Zoysiagrass (highly susceptible variety)
Multiple growing seasons to capture seasonal variations
The results from these experiments reaffirmed the critical role of environmental modulation and proper cultural techniques in disease suppression . Specifically, the research identified key factors influencing disease development:
| Factor | Low-Risk Condition | High-Risk Condition | Effect on Disease |
|---|---|---|---|
| Soil Moisture | Well-drained, moderate irrigation | Poor drainage, overwatered | 3x higher severity in saturated soils |
| Soil pH | Neutral (6.5-7.0) | Acidic (<6.0) | 2.5x increase in acidic conditions |
| Nitrogen Fertilization | Early summer application | Spring application | 80% higher severity with spring feeding |
| Thatch Depth | <0.5 inches | >1 inch | 2x higher severity with thick thatch |
| Soil Salinity | Low to moderate | High | 1.8x increase in saline conditions |
These findings have transformed extension recommendations for turf professionals and homeowners, emphasizing the importance of modifying cultural practices rather than relying solely on fungicides for control.
The single strongest predictor of disease severity, with saturated conditions dramatically increasing infection rates.
Soil pH below 6.0 significantly increased disease susceptibility, while values near neutral (7.0) provided protection.
Nitrogen fertilization timing profoundly influenced disease, with spring applications exacerbating problems.
Effective management of large patch requires an integrated approach that begins with proper cultural practices. As Hutchens noted, many people inadvertently worsen large patch problems through well-intentioned but misguided practices like overwatering 3 . The research consistently shows that simple adjustments to maintenance routines can significantly reduce disease severity:
When cultural practices alone prove insufficient, targeted fungicide applications may become necessary. The research highlights that timing is absolutely critical for effectiveness . Preventative applications in early fall, when soil temperatures drop into the favorable range for fungal activity (50°F–70°F), provide significantly better control than curative applications after symptoms appear.
Monitor soil temperatures in autumn and apply fungicides when temperatures consistently fall below 70°F for best preventative results.
Rotate between chemical classes to prevent the development of fungicide resistance in pathogen populations.
The review highlights breeding for genetic resistance as a promising frontier for sustainable large patch management . Current turfgrass breeding programs are increasingly incorporating disease resistance as a key selection criterion, though this remains challenging due to the complex genetics involved.
Identification of resistant cultivars and the incorporation of resistance genes through traditional or molecular breeding could significantly reduce reliance on chemical controls while improving long-term disease resilience. Such endeavors require robust phenotyping protocols and a deeper understanding of the genetic bases underpinning host-pathogen interactions within warm-season turfgrass species.
Key research materials and their functions in studying large patch disease
| Research Tool | Primary Function | Application in Large Patch Research |
|---|---|---|
| Selective Media | Fungal isolation and identification | Allows researchers to isolate Rhizoctonia solani from soil and plant tissue |
| Soil Moisture Sensors | Continuous monitoring of soil water content | Correlates irrigation practices and rainfall with disease outbreaks |
| Digital Phenotyping | High-resolution disease assessment | Provides objective measurement of patch size and disease severity |
| Weather Stations | Microclimate monitoring | Tracks temperature, humidity, and rainfall at research sites |
| Soil Testing Kits | Analysis of chemical properties | Measures pH, salinity, and nutrient levels influencing disease |
| Molecular Markers | Genetic identification | Differentiates between fungal strains and identifies resistant grass varieties |
Large patch disease represents a fascinating intersection of plant pathology, soil science, and turfgrass management, demanding integrated solutions rooted in both fundamental biological understanding and practical application . The recent comprehensive review led by Samuel Kreinberg provides an invaluable synthesis of existing knowledge while charting a course for future research directions.
For homeowners and turf professionals battling this stubborn adversary, the insights from this research offer both explanation and empowerment. Understanding the environmental triggers, recognizing the seasonal patterns, and implementing proper cultural practices can dramatically reduce the impact of this disease. As climate variability intensifies and user demands on turfgrass systems evolve, this continuous research and adaptive management will prove increasingly indispensable .
The University of Arkansas System Division of Agriculture, through its Agricultural Experiment Station and Cooperative Extension Service, continues to bridge the gap between scientific discovery and practical application 3 . Their work ensures that the evolving scientific understanding of turfgrass diseases like large patch benefits a broad audience, from individual lawn owners to professional turf managers, promoting healthier and more resilient grass landscapes for future generations.
The next time you notice those expanding brown patches in a spring lawn, remember—you're not just seeing a dying lawn, but witnessing a complex biological drama that scientists are steadily working to unravel. Through their efforts, the promise of lush, healthy turfgrass becomes increasingly attainable for everyone.