Understanding Brown patch disease in turf management

Effective management of brown patch involves understanding its causes, identifying symptoms early, and implementing appropriate cultural and chemical control strategies.

Causes

Brown patch disease is driven by a combination of environmental factors and turf management practices. Key contributing factors to brown patch outbreaks include:

• High Humidity: Prolonged periods of high humidity create favourable conditions for Rhizoctonia solani.
• Warm Temperatures: Brown patch is most aggressive during periods of warm temperatures, particularly when nighttime temperatures stay above 17°C.
• Turf Stress: Poor turf health due to stress factors such as excessive nitrogen, low mowing heights, and excessive thatch increases susceptibility to Brown patch.
• Thatch Accumulation: Thatch provides a conducive environment for fungal spores to survive and germinate.

Identification

Identifying brown patch involves looking for specific symptoms on the turfgrass:

• Brown, Circular Patches: Affected areas typically appear as circular patches of brown, dead grass, ranging from a few inches to several feet in diameter.
• Mycelium Presence: Under high humidity, brown patch produces a white or light brown mycelium on the grass surface, especially during the early morning hours.
• Leaf Lesions: Lesions often appear on the leaves as tan or brown spots with dark brown borders.
• Rapid Turf Decline: Infected areas can deteriorate quickly, leading to large, unsightly patches of damaged turf.

Brown patch

Cultural Management Strategies

Implementing effective cultural management practices can significantly reduce the risk and severity of brown patch disease:

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 harbor fungal 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 brown patch 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 brown patch 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 Brown patch control. Effective fungicides include Ascernity and Heritage.
• Instrata Elite and Medallion TL can also be used as part of a fungicide rotation program to prevent resistance development.

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 brown patch 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 brown patch disease and maintain healthy, resilient turfgrass.