Dollar spot in bermuda grass is a common and frustrating disease that thrives in warm, humid conditions. This fungal infection, caused by Sclerotinia homoeocarpa, targets the leaf blades and disrupts the plant's ability to photosynthesize effectively. Homeowners and groundskeepers often notice small, circular patches that resemble silver dollars, hence the name. Early detection is crucial to prevent the disease from spreading across the entire lawn, turning a lush green carpet into a damaged and unsightly yard.
Identifying the Symptoms
Recognizing the visual signs is the first step in combating this issue. The most distinct characteristic is the appearance of straw-colored, sunken lesions on the leaf blades. These lesions often have a reddish-brown border, which makes them stand out against the healthy green tissue. As the disease progresses, the spots expand and merge, forming the characteristic circular patches that are typically the size of a silver dollar or larger. In the early morning or during high humidity, you might also observe a fine, cobweb-like mycelium covering the affected areas.
Distinguishing from Other Lawn Diseases
It is easy to confuse dollar spot with other common lawn ailments, such as brown patch or Pythium blight. However, there are key differences that set it apart. Unlike brown patch, which usually affects the base of the plant and creates large, irregular brown areas, dollar spot specifically targets the leaf blades while the crown and roots often remain healthy. Furthermore, the lesions are relatively uniform in size and have a distinct tan color with a reddish margin, whereas brown patch lesions are often water-soaked and dark. Proper identification ensures you apply the correct treatment strategy.
Causes and Favorable Conditions
The disease thrives in specific environmental conditions that favor the fungus over the grass. Warm temperatures between 80°F and 90°F, combined with high humidity, create the perfect storm for an outbreak. Nighttime dew or prolonged leaf wetness are critical factors, as the fungus requires moisture to spread. Lawns that suffer from drought stress or have low nitrogen levels are particularly vulnerable, as the weakened grass struggles to defend itself against the invasion.
High humidity levels above 90%
Insufficient nitrogen in the soil
Overwatering leading to wet foliage
Thatch buildup preventing air circulation
Mowing when the grass is wet
Effective Treatment Strategies
Once the disease is confirmed, immediate action is necessary to save the lawn. Fungicides containing active ingredients such as azoxystrobin, propiconazole, or thiophanate-methyl are highly effective at controlling the spread. It is essential to apply these products according to the label instructions, ensuring thorough coverage of the affected areas. Systemic fungicides are often preferred because they are absorbed by the plant and provide long-lasting protection against reinfection.
Cultural Practices for Recovery
Chemical treatments work best when combined with improved cultural practices. Adjusting your mowing height to the recommended level for bermuda grass helps the plant conserve energy for recovery. Avoiding heavy nitrogen fertilizers during the outbreak is advised, as they can promote excessive top growth that is more susceptible to disease. Instead, opt for a balanced fertilizer once the threat has passed to strengthen the grass blades and improve overall resilience.
Preventative Measures for Long-Term Health
Preventing dollar spot is significantly easier than treating it after the damage is done. Implementing a consistent lawn care routine reduces the risk of future outbreaks. Morning watering allows the grass blades to dry quickly, depriving the fungus of the moisture it needs to germinate. Aerating the soil annually alleviates compaction and improves drainage, while regular dethatching removes the debris that traps moisture near the crown of the plant.
