St. Augustine grass is popular for residential and commercial lawns and golf courses. Its thick turf and lush greenery can transform any property into the envy of the entire neighborhood.
However, this turf grass is known to fall prey to fungal diseases like the grey leaf spot, especially during the warm and humid weather.
If left unchecked, the disease can kill large patches of grass, making your lawn unhealthy and unsightly.
In this article, we’ll assist you in accurately identifying the disease and provide expert-recommended treatments that will help recover and keep your St. Augustine lawn thriving.
What is Grey Leaf Spot: Symptom Identification
The grey leaf spot is a fungal disease caused by the Pyricularia grisea. It mostly attacks the grass during the hot, rainy periods. The disease can also be encouraged by extended periods of overwatering and leaf wetness from dew or rain.
One of the first signs to look out for when identifying the disease are the grey oval leaf spots on the leaves. They initially start as small and brown spots but grow into large oblong lesions that appear on the leaf blades.
Here are some symptom pointers to correctly identify the grey leaf spot disease:
- Small or large oval spots on the leaves that are typically gray with a dark brown or purplish border.
- First, check for the spots in the shaded or moist areas and look for the progressive spread outward to other patches.
- The affected patches may begin to thin out and appear drought-stressed or scorched even when the soil moisture is adequate.
- As the disease progresses, the leaves may turn yellow and die off.
The disease typically affects new turf growth more frequently than already established grass. However, other causes that may increase a turf susceptibility to the disease:
- Improper irrigation practices such as overwatering or watering late in the day.
- Excessive applications of nitrogen fertilizer in the summer.
- Compacted soil and thatch buildup.
- Nutrient imbalance or deficiency.
- Growing susceptible turf varieties like the Palmetto.
Since the disease spreads fast, a timely and accurate identification is crucial to avoid costly treatments. As soon as you confirm the infestation, implement the right measures to treat the disease.
Grey Leaf Spot Treatment Options
Whether the disease infestation is small or is ravaging half your lawn, you can stop it and reclaim your turf.
The control measures are:
1. Improving Cultural Practices
A vital turf grass management practice that discourages the spread of the disease is proper irrigation. Water early in the day to reduce the duration of leaf wetness. Also, water deeply but infrequently — once a week, with about an inch of water is enough for most St. Augustine cultivars.
Fertilization completed under the right weather conditions (less than 85°F) can also prevent and reduce grey leaf spot infestations.
2. Chemical Treatment
The most effective treatment for grey leaf spot is fungicides. Products containing active ingredients such as fluoxastrobin, azoxystrobin, propiconazole, thiophanate-methyl, and pyraclostrobin offer excellent to good control.
Exclusive use of one product can lead to fungicide resistance. Experts recommend alternating the fungicides or using products that have two active ingredients.
Make sure to read the label and apply as directed.
Lead Editor for Insight Weeds.