What Is Necrotic Ring Spot & How To Treat It

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Necrotic Ring Spot (NRS), caused by the soilborne fungus Ophiosphaerella korrae, is a formidable foe for lawns and grassy areas. This insidious disease manifests as unsightly circular patches of dying grass, often forming distinctive rings or arcs. Left unchecked, NRS can significantly impact your turf's aesthetics and overall health. However, you can effectively combat this pervasive lawn disease with a comprehensive understanding of its identification, treatment strategies, and preventative measures.

Identifying Necrotic Ring Spot

NRS exhibits distinct visual characteristics that allow for early detection. The hallmark symptom is the presence of circular patches of dead or declining grass. These patches typically begin small, measuring only a few inches in diameter, and gradually expand over time into well-defined rings or arcs that can reach several feet or even meters across.

  • Growth Pattern: A closer inspection of the affected areas often reveals a straw-colored or sunken appearance at the center of the ring. This central zone is frequently surrounded by a band of healthy-looking, green grass, creating a striking visual contrast. In some instances, a keen eye may detect dark fungal structures, such as hyphae and pseudosclerotia, clinging to the diseased grass blades.
  • Seasonal Patterns Of Necrotic Ring Spot: While NRS can technically appear throughout the growing season, its peak activity coincides with warm, humid weather and moist soil conditions. This typically translates to late spring through early fall, a period when fungal growth flourishes.

Understanding The Life Cycle Of Necrotic Ring Spot

Unlocking the life cycle of NRS is crucial for developing an effective management strategy. Here's a breakdown of the key stages:

  • Inoculation and Infection: The journey begins in cool, wet conditions during spring or autumn, when the fungus Ophiosphaerella korrae infects the grass roots and crowns.
  • Colonization: The fungus establishes itself within the root system, disrupting the vital flow of water and nutrients. This disruption leads to the development of characteristic rings or patches of dead grass.
  • Symptoms Development: The telltale signs of NRS, such as yellowing and death of grass blades, typically become apparent during periods of environmental stress, particularly in late spring and summer.
  • Spore Production and Dissemination: The fungus produces spores, microscopic reproductive units, which can be readily spread by water, wind, or even mechanical means like lawnmowers or gardening tools. These spores then infect new areas, perpetuating the cycle of disease.
  • Dormancy: With the arrival of winter, the fungus enters a dormant state, residing within infected plant debris or the soil itself. It remains poised to re-infect the lawn in the next growing season.

Combating & Preventing Necrotic Ring Spot

Managing NRS necessitates a multifaceted approach, employing a combination of cultural practices and, in some cases, targeted interventions. A healthy lawn, nurtured through proper watering, mowing, and fertilization practices, is naturally more resilient to disease.

  • Enhanced Drainage: Aeration is paramount. By aerating the affected areas, you improve air circulation and soil drainage. This creates an environment less conducive to fungal growth.
  • Water Management: Overwatering is detrimental, as it fosters fungal proliferation. Implement a deep watering regimen, focusing on infrequent but thorough saturation to encourage deep root growth.
  • Mowing Practices: Maintain proper mowing heights and avoid scalping the lawn. Scalping can stress the turf, making it more susceptible to disease.
  • Balanced Fertilization: Ensure balanced soil fertility by avoiding excessive nitrogen fertilization. Excessive nitrogen can exacerbate fungal growth. Conduct a soil test to determine the appropriate nutrient levels and fertilize accordingly.
  • Fungicides: When necessary, fungicides can be employed to mitigate fungal activity and support turf recovery. However, it's important to note that fungicides may not completely eradicate the disease. Always use fungicides specifically labeled for NRS and meticulously follow the manufacturer's application instructions. Consulting a professional lawn care specialist before applying fungicides is highly recommended.
  • Beneficial Organisms: Research on utilizing beneficial fungi or bacteria as biological control agents for NRS shows promise. While more studies are needed for widespread adoption, this method may emerge as a viable option in the future.

Call Heartland For Lawn Disease Control

While Necrotic Ring Spot presents a significant challenge to lawn health, a comprehensive approach combining identification, treatment strategies, and preventative measures empowers you to combat this disease effectively. By implementing cultural practices that optimize drainage and promote turf health, coupled with targeted interventions like fungicides when necessary, you can safeguard your lawn from the detrimental effects of NRS. Remember, early detection and proactive management are key, so why not call the professionals here at Heartland Turf & Landscape to stay on top of your NRS for you? 

Our technicians have years of experience in the field, and calling us at the first hint of NRS invading your turf is the best way to prevent any serious damage to your lawn. If you are in the Kansas City area and need help identifying or treating lawn disease on your property, contact us now to get started!