SUMMER PATCH PATHOGEN

SUMMER PATCH DISEASE IN TURFGRASS: UNDERSTANDING MAGNAPORTHE POAE AND ITS IMPACT IN NORTHERN BEIJING

 

INTRODUCTION
Summer 2023 brings heightened concerns for turfgrass health in the northern Beijing region, as the prevalence of Summer Patch disease, caused by the pathogen magnaporthe poae, continues to rise. This article delves into the working mechanisms of this pathogen and its implications in plant pathology. Additionally, we explore effective management strategies and highlight some of the latest fungicides recommended by the Thompson Golf Management (TGM).

 

UNDERSTANDING MAGNAPORTHE POAE
Magnaporthe poae, a fungus, plays a central role in causing Summer Patch disease. It survives unfavorable conditions through mycelium in infected plant tissue or debris. Optimal growth occurs at 28°C, and infection takes place during late spring when soil temperatures reach 19-20°C. The fungus spreads between turfgrass roots, with symptoms often remaining dormant until triggered by a significant temperature increase during wet weather. Furthermore, this pathogen can be transmitted through the movement of infected plant material and mechanical equipment, exacerbating its prevalence and impact.

 

IMPACT ON PLANT PATHOLOGY
Summer Patch disease caused by M. poae affects turfgrass, including Kentucky bluegrass (poa pratensis), annual bluegrass (poa annua), and fescues (festuca sp.), common in the northern Beijing region. The disease leads to a root and/or crown rot, resulting in scattered small patches of thin, wilted, or slow-growing turf. The affected areas vary in size, ranging from 3-8 cm initially but potentially expanding to 30 cm in diameter. Patches exhibit colors from gray-green to light tan or straw-colored and may coalesce to form crescents of yellow or tan turf. Microscopic examination is often necessary to distinguish Summer Patch from other diseases like Necrotic Ring Spot, which may display similar symptoms. Additionally, infected plant tissue presents dark brown roots, crowns, and stolons as the dark mycelium invades the tissue, ultimately leading to the rotting of the cortex and plant mortality.

MANAGEMENT STRATEGIES IN NORTHERN BEIJING
Effective management of Summer Patch disease is critical to maintaining the health and aesthetics of turfgrass in the Beijing region. Addressing primary stresses, including excess thatch, fertilizer, and turf canopy temperature, as well as improper timing of fertilizer applications, low mowing height, and pH extremes, is essential.

To mitigate disease severity, focus on cultural practices such as maintaining soil and rhizosphere pH levels between 5.5 and 6.0 and using acidifying fertilizers when pH exceeds 6.0. Proper fertilization practices, applying two to five lbs of nitrogen per 1000 sq. ft., should be followed. Avoid fertilizer application during the stress period (June to August) and only fertilize in autumn and late spring.

In the dry summer periods, ensure deep & infrequent watering to promote proper root growth. Consider using soaker hoses for supplementary watering on steeper slopes to enhance efficiency and infiltration rates. Lightly syringe the surface during mid-day to reduce harmful temperature effects.

Maintain an appropriate cutting height and mow frequently enough to remove less than 1/3 of the leaf blade during each mowing session. Manage thatch, ensuring it does not exceed 1.5 cm in thickness through practices like verti cutting, aeration, and topdressing during spring and early fall.

 

RECOMMENDED FUNGICIDES BY TGM FOR SUMMER PATCH DISEASE
For Beijing’s turfgrass management, TGM recommends the following latest fungicides to combat Summer Patch disease effectively:
• Fungicide A: Ascernity, benzovindiflupyr + difenoconazole
• Fungicide B: Honor Intrinsic, boscalid + pyraclostrobin
• Fungicide C: Posterity, azoxystrobin + propiconazole + pydiflumetofen

Thoroughly water the areas with a history of this disease several days before applying the fungicide. Monitor soil temperature to a depth of 2 inches and make the first application when the soil temperature reaches 55°F or about 13°C. Additional applications may be necessary, depending on soil temperature and disease severity. Always adhere to the rates and procedures recommended on the fungicide package label.

CONCLUSION
The emergence of Summer Patch disease caused by Magnaporthe poae presents a significant challenge to turfgrass health in the Beijing region during Summer 2023. Understanding the pathogen’s working mechanisms and its impact on plant pathology is crucial for effective management. Employing appropriate cultural practices and employing the latest recommended fungicides by TGM will ensure the resilience of your turfgrass playing surfaces, mitigating the adverse effects of this devasting disease.

http://plantclinic.cornell.edu/factsheets/
summerpatch.pdf

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