Understanding Pythium disease in turf management

Pythium disease is particularly problematic in stadium environments where high humidity, poor air circulation, and frequent irrigation create ideal conditions for the disease to thrive.

Causes

Pythium disease is caused by soil-borne oomycetes, which are fungus-like organisms but belong to a different biological class. These pathogens flourish in water-saturated soils and spread rapidly through water movement. Key contributing factors to Pythium outbreaks include:

• High Soil Moisture: Over-irrigation, poor drainage, and heavy rainfall create conditions favourable for Pythium growth.
• High Temperatures: Pythium blight is most aggressive during periods of high temperatures combined with high humidity.
• Poor Air Circulation: Enclosed environments like stadiums trap heat and moisture, exacerbating the conditions that favour Pythium development.
• Thatch Accumulation: Thatch provides a conducive environment for Pythium spores to survive and germinate.

Identification

Identifying Pythium disease involves looking for specific symptoms and signs on the turfgrass:

• Greasy or Water-Soaked Appearance: Affected areas often appear greasy and water-soaked, with a dark, slimy texture.
• Rapid Turf Decline: Pythium can cause rapid and severe turfgrass wilting and collapse, often within a day or two.
• Mycelium Presence: Under high humidity, Pythium produces a fluffy, white mycelium on the grass surface, especially during the early morning hours.
• Distinct Patches: Infected areas can develop into irregular, distinct patches that expand rapidly if conditions remain favourable.

Pythium

Cultural Management Strategies

Cultural management practices play a crucial role in preventing and controlling Pythium disease. Implementing these strategies can reduce the risk of severe outbreaks:

Water Management:

• Avoid over-irrigation and ensure proper drainage to reduce soil moisture levels.
• Water deeply but infrequently to encourage deep root growth and reduce surface moisture.

Improve Air Circulation:

• Prune surrounding vegetation and manage landscape features to enhance airflow around the turf.
• Consider using fans in enclosed stadiums to reduce humidity and dry the turf canopy.

Thatch Management:

• Regularly aerate and dethatch the turf to reduce organic matter accumulation, which can harbour Pythium spores.
• Topdress with sand to improve soil structure and drainage.

Avoid Nighttime Irrigation:

• Watering in the early morning allows the turf to dry quickly, reducing the duration of leaf wetness, which is crucial for Pythium development.

Fertility Management:

• Maintain balanced fertility levels to promote healthy turf growth and reduce stress.
• Avoid excessive nitrogen applications, especially during periods of high disease pressure.

Chemical Control

When cultural practices are not sufficient to control Pythium disease, chemical interventions may be necessary.

Fungicides can provide effective control, especially when applied preventatively or at the first sign of disease.

Fungicide Selection:

• Use fungicides specifically labelled for Pythium control. In this case, Heritage is recommended as the go-to fungicide for Pythium blight. Heritage, containing azoxystrobin, is effective against Pythium due to its systemic action.
• Avoid using fungicides like Instrata Elite and Medallion TL for Pythium, as they are less effective against this particular pathogen.

Application Timing:

• Apply fungicides preventatively during periods of high risk, particularly before extended periods of warm, wet weather.
• For curative applications, act quickly at the first sign of disease to halt progression.

Proper Application Techniques:

• Ensure thorough coverage of the turf canopy and root zone, as Pythium pathogens can be present both on the foliage and in the soil.
• Follow label instructions regarding rates, intervals, and application methods to maximise efficacy.

Conclusion

By understanding the causes, identifying symptoms early, and implementing effective cultural and chemical management strategies, turf managers can significantly reduce the impact of Pythium disease and maintain healthy, resilient turfgrass during periods of high-risk of attack.