Summer Disease Vigilance

A practical perspective

I’ve seen summer turf diseases take hold rapidly, wiping out areas of newly sown ryegrass in conditions that seemed entirely manageable the day before. These diseases can infect the turf surface incredibly fast — and can be unforgiving.

Now, in my role with ICL, I’m supporting venues across the UK and Ireland — not just with product advice, but by helping grounds teams interpret conditions, plan disease management strategies, and strengthen decision-making. This article outlines some of the key summer disease threats, the environmental triggers to watch for, and how to build a robust and practical response.

Why vigilance is essential

The summer months present a paradox for turf managers of elite sports pitch surfaces. While warm temperatures and extended daylight hours drive turf growth and recovery, they also create the perfect storm for destructive turfgrass diseases. Newly established turf, particularly perennial ryegrass (Lolium perenne) swards on sand-based rootzones, is especially vulnerable due to:

• Intensive renovations: High-spec renovations often involve high nitrogen inputs and frequent irrigation, increasing disease susceptibility.
• Zero tolerance for damage: Unlike golf greens where some damage might be tolerated, stadium and training ground pitches demand immaculate playing surfaces all season, meaning even minor disease outbreaks can have serious consequences.
• Microclimates in stadia: Enclosed or semi-enclosed stadium environments can trap humidity and restrict air movement, fostering conditions that favour pathogen development.
• Increased foot traffic and wear: The return of pre-season training and friendly fixtures in July and August adds additional plant stress, further weakening the turf’s natural defences.

A proactive approach is crucial. Understanding the conditions that drive disease outbreaks and recognising early symptoms allows for timely cultural and chemical interventions. Below, we explore four of the most common summer turf diseases and how to manage them.

1. Pythium blight (Pythium spp.)

Conditions to watch out for:

• High temperatures and humidity: Outbreaks are common when daytime temperatures exceed 27°C and nighttime temperatures remain above 20°C.
• Excess surface moisture: Poor drainage, excessive irrigation, and prolonged leaf wetness create ideal conditions.
• Dense, juvenile growth: Newly germinated ryegrass is particularly at risk, especially in stadia with poor airflow.

How to identify Pythium Blight:

• Greasy, water-soaked patches: Dark, slimy patches often appear overnight.
• Rapid turf collapse: Entire patches can wilt and die within 24–48 hours.
• Fluffy mycelium: Cottony white growth may be visible in the early morning under humid conditions.

Management strategies:

• Reduce leaf wetness: Water deeply but infrequently, avoid evening irrigation, and improve drainage. Use an appropriate wetting agent to drive moisture into the rootzone and avoid excess surface wetness.
• Increase airflow: Prune vegetation and consider fans in enclosed stadia.
• Clean machinery and footwear: Use appropriate disinfectants on equipment and for staff and players.
• Fungicide protection:
  • Preventative: Apply Heritage (azoxystrobin) ahead of prolonged warm and humid periods.
  • Curative: Apply FR321 (azoxystrobin + fludioxonil + Ryder). Act immediately at first symptoms — Pythium spreads rapidly via water.

Pythium blight

2. Grey leaf spot (Pyricularia grisea)

Conditions to watch out for:

• Warm, humid weather: Prolonged daytime temperatures above 25°C and night-time temperatures above 20°C with high moisture.
• Juvenile ryegrass: Particularly aggressive on newly sown turf.
• Nitrogen-driven growth: Excess nitrogen creates tender, susceptible tissue.

How to identify Grey leaf spot:

• Small, water-soaked lesions: Appear greyish on leaf blades.
• Twisting & wilting: Leaves curl, twist and collapse, thinning the turf.
• Greyish, velvety spores: Outbreaks may result in a spore mass on the surface.
• Larger areas appear dry & shrivelled.

Management strategies:

• Nitrogen management: Avoid excessive applications of immediately available nitrogen. Use slow release and controlled-release fertilisers.
• Cultural practices: Increase airflow (using fans in stadiums), reduce organic matter accumulation, and avoid excess surface moisture.
• Irrigation management: Water deeply and less frequently using a wetting agent like Qualibra. Avoid evening irrigation and prolonged leaf wetness.
• Use resistant cultivars: Choose cultivars with known resistance to GLS.
• Clean/disinfect machinery & footwear.
• Fungicide protection:
  • Preventative: Ascernity (difenoconazole + SOLATENOL) or Instrata Elite (difenoconazole and fludioxonil) in high-risk conditions.
  • Curative: Use Medallion TL (fludioxonil) for contact action during severe outbreaks.

Grey leaf spot

3. Brown patch (Rhizoctonia solani)

Conditions to watch out for:

• Warm, moist conditions: Especially when nighttime temperatures stay above 17°C.
• Lush turf & excess organic matter: Risk increases with over-fertilisation, overwatering, and organic matter buildup.

How to identify Brown Patch:

• Circular, brown patches: 10 cm to 1 m wide, sometimes with smoky rings.
• Morning mycelium: Brown mycelium visible on dewy mornings.
• Leaf lesions: Irregular tan lesions with dark borders.

Management strategies:

• Water management: Irrigate in the early morning and avoid excess water.
• Organic matter control (if not a full renovation): Aerate and top dress with an appropriate sand to reduce thatch build up and improve drainage.
• Fungicide protection:
  • Preventative: Ascernity (difenoconazole + SOLATENOL) or Heritage (azoxystrobin).
  • Curative: Instrata Elite (difenoconazole + fludioxonil) or Medallion TL (fludioxonil) when symptoms appear.

4. Leaf spot diseases

Leaf spot diseases are common in intensively managed sports turf, especially where stress, compaction, and disease pressure coincide.

Conditions to watch out for:

• Cool or warm temperatures.
• Prolonged damp surface conditions.
• Overfeeding with nitrogen (soft, succulent growth).
• Nutrient deficiencies.
• Overwatering.
• Close mowing.
• Surface compaction.
• Shade and poor air movement.

How to Identify Leaf spot:

• Three main pathogens: Bipolaris spp. (more common in summer), with Curvularia spp. and Drechslera spp. also present, particularly on seedlings.
• Small dark yellow, brown or black lesions on leaf blades, progressing to larger spots with dark margins and leaf dieback.

Management strategies:

• Reduce surface compaction.
• Balanced nutrition: include micronutrients.
• Sharp mower blades.
• Avoid excess irrigation.
• Fungicide protection:
  • Preventative: Ascernity (difenoconazole + SOLATENOL) or Instrata Elite (difenoconazole + fludioxonil).
  • Curative: Medallion TL (fludioxonil) in case of outbreaks.

Brown patch

Summary

Each site has its own microclimate, renovation pressures, and performance expectations. But across all venues, the key elements of disease prevention remain consistent:

• Observation: Monitor surface moisture, canopy density, and weather conditions.
• Early identification and action: React quickly at the first signs.
• Cultural control: Improve airflow, manage thatch, and avoid excess nitrogen.
• Planned fungicide use: Rotate actives, apply in line with conditions, and act before issues escalate.

Managing disease through the summer doesn’t need to be a firefight. With the right foundations and a clear plan, it becomes just another part of good surface management.