Introduction: Take-all patch disease stands out as one of the formidable challenges faced by gardeners, even though it’s a relatively rare occurrence. Stemming from the fungus Gaeumannomyces graminis, previously known as Ophiobolus graminis, this disease wreaks havoc by decimating the roots and stems of bent grass in lawns. Afflicted bent grass tends to easily detach from the turf, a result of the deteriorating roots.
Identification: The onset of the disease is typically noticeable around mid-summer, with initial manifestations occurring as small, expanding circular patches ranging from 50cm to 100cm in diameter. Notably, only the bent grass is affected. Dead or decaying rings of straw-colored bent grass might have patches of resistant grasses and weeds inside. As the disease progresses, these patches can coalesce, leading to widespread damage. Although take-all patch usually recedes post-December, it can recurrently plague the lawn for multiple years. However, as antagonistic bacteria counteract the disease over time, its eventual complete disappearance is likely, making a recurrence improbable.
Favorable Conditions: Several conditions can exacerbate the prevalence of take-all patch disease:
- Soil pH: Any treatment, like liming, which elevates the root zone’s pH can be a catalyst for the disease.
- Nutrient Deficiency: Soils lacking essential nutrients are susceptible.
- Soil Type: Light, sandy soils, inherently deficient in antagonistic bacteria, can be breeding grounds for the fungus responsible for take-all patch.
- Lawn Wetness: A wet, thatchy lawn is a conducive environment for the disease to spread among soil particles.
Prevention & Control: Given the challenges of controlling the disease once it has established a foothold, and the unavailability of fungicides to amateur gardeners, prevention becomes paramount. Some cultural practices to consider are:
- Soil pH Management: Abstain from practices that increase soil pH, like liming. If liming is unavoidable, subsequent applications of lawn sand or iron sulphate can help acidify the lawn surface, staving off the disease.
- Seed Selection: Opt for resistant grass seed mixtures, such as those containing fescue and ryegrass, which remain unaffected by the disease.
- Nutrient Management: Implement a balanced fertilizer regime. Some theories suggest that magnesium applications can help suppress the disease.
- Aeration: Regular aeration not only dispels surface water (since the disease proliferates in wet conditions) but also augments soil bacteria that inhibit the disease.
- Scarification: Regular scarifying can help eliminate excess thatch and organic matter, which can harbor the disease.
Conclusion: Take-all patch disease, though not common, can be a formidable adversary for your lawn. A combination of vigilant observation and proactive lawn care practices can help manage and eventually eliminate this pesky challenge.
