Brown spots on lawn?
The culprit is a fungal disease known as, Ascochyta leaf spot. Conditions that favor Ascochyta are not well understood, but usually brown spots on lawns occur just after unseasonably warm weather preceded by cool and wet weather.
Water droplets from precipitation and irrigation splash fungal spores onto individual grass blades. When the turf grass becomes water stressed the disease is able to infect the plant.
Nearly overnight, the affected grass plants bleach out turning the grass into a straw-like color. The grass patches appear dead, however only the grass blades are affected – the roots are unharmed. Close examination of the leaf blade reveals that the bleached out part of the grass plant has a pinched appearance.
Ascochyta appears in the spring and summer months. Infections that occur this time of year usually recover with cooler temperatures. Summer infections are slow to recover and may only do so with cooler fall weather. Proper lawn care in Colorado can help prevent this issue.
What should you do?
- If not already completed, have your lawn aerated.
- Set your mower to a height of 2 ½ to 3 inches and make sure your mower blade is sharp. Do not mulch your lawn if you have ascochyta.
- Keep mower wheels and shoes used when cutting the lawn clean, as this can spread the fungus.
- Continue with a balanced fertility program. Do not increase fertilization to promote recovery.
- Check your irrigation system to ensure complete coverage. Water the affected area with more water and less often. Limit your watering to the early morning hours so that the grass plant will dry quickly.
- Apply a soil conditioner that promotes water penetration may also promote recovery.
To help prevent a similar occurrence of brown spots on your lawn later in the summer, sharpen your mower blade monthly and check your sprinkler coverage frequently. Within the confines of water restrictions, increase and decrease your irrigation schedule as the summer temperatures change.