Short Answer: The spring lawn diseases we see most often across Jacksonville and St. Augustine are large patch (on St. Augustine, Zoysia, and Centipede), gray leaf spot (the defining St. Augustine disease), take-all root rot (on Bermuda and St. Augustine), and dollar spot (on Bermuda and Zoysia). Catching them early (circular yellow-orange rings, water-soaked patches along edges, thinning slow-green Bermuda, small bleached spots) saves significant recovery time. Below is the field guide for Northeast Florida lawns, from Ponte Vedra to Atlantic Beach to Fernandina Beach.
You walk out one April morning in Jacksonville, Ponte Vedra, or St. Johns and notice something new. A yellow-orange ring forming in your St. Augustine near the back patio. Grayish lesions on individual blades that were green a week ago. Or a Bermuda area that is just not greening up the way it did last April.
Northeast Florida’s climate, with warm year-round temperatures, high humidity, frequent afternoon rain, and sandy soils, creates ideal fungal conditions. The good news is that early identification is straightforward once you know what you are looking at.
Large Patch: The Dominant Spring Disease
Large patch is the most common spring lawn disease we see across Jacksonville and St. Augustine. It affects St. Augustine, Zoysia, and Centipede lawns alike.
What it looks like: circular or irregular yellow-orange patches ranging from 3 feet to more than 30 feet across. Edges are typically bright yellow-orange, interior grass is thin and brown. Usually appears first in low, wet areas and shady spots where moisture lingers.
Why it shows up in spring: Rhizoctonia solani AG2-2 LP thrives at 60 to 75 degree soil temperatures with high moisture. Jacksonville’s spring humidity and frequent rain make April and May peak season.
What to do: reduce nitrogen (heavy spring fertilizer directly feeds the fungus), improve drainage in wet spots, and apply targeted fungicide if active. A preventive fungicide in fall often shuts down spring outbreaks before they start.
Gray Leaf Spot: The St. Augustine Problem
Gray leaf spot is specific to St. Augustine grass and shows up heavily in humid conditions. If you have St. Augustine in Jacksonville, you will encounter this disease eventually.
What it looks like: small gray-to-tan oval lesions with dark or purple borders on individual grass blades. Severe infection causes leaves to die back and patches to thin. Often starts in heavily watered or heavily fertilized areas, particularly in the shade of mature oaks common in Riverside and Ortega neighborhoods.
Why it shows up: Pyricularia grisea loves warm, humid weather, which describes Jacksonville summer perfectly. Excess nitrogen is a direct contributor.
What to do: reduce nitrogen, water deeply but less frequently (never in the evening), raise mowing height on St. Augustine to 3.5 to 4 inches. Apply fungicide if outbreak is active.
Take-All Root Rot: The Bermuda and St. Augustine Sneak
What it looks like: thinning, irregularly shaped yellow or pale areas that are slow to green up in spring. When you pull a handful of grass, roots look short, dark, and rotted instead of healthy and white.
Why it shows up: Gaeumannomyces graminis attacks roots of warm-season grasses when cool, wet soil conditions persist into early spring. Jacksonville’s sandy soils with high water tables and cool late-winter periods create openings.
What to do: soil test and check pH (high pH is a common factor in Florida). Correct with sulfur if pH is above 7.0. Address manganese deficiency with foliar applications. Fungicide for severe cases plus cultural improvements like adjusted irrigation.
Dollar Spot on Bermuda and Zoysia
What it looks like: small bleached patches about the size of a silver dollar. Individual blades have hourglass-shaped lesions. Early morning dew may reveal cobweb-like fungal growth.
Why it shows up: nitrogen-deficient lawns. Common on Jacksonville lawns that skipped fall feeding or that are in the recovery phase from other stresses.
What to do: a balanced fertilizer application often resolves dollar spot in its tracks. Fungicide for heavier outbreaks.
Three Habits That Prevent Most Jacksonville Spring Disease
- Water in the early morning only, 1 inch per week. Evening watering is the single biggest driver of fungal outbreaks in Northeast Florida. Set irrigation to 4 to 7 a.m.
- Reduce spring nitrogen on St. Augustine and Zoysia. Heavy feeding drives both large patch and gray leaf spot. The Miami-Dade summer restrictions that do not apply here still teach the right lesson: less is more for these grasses.
- Mow at the right height. St. Augustine: 3.5 to 4 inches. Zoysia: 2 to 3 inches. Bermuda: 0.5 to 1.5 inches for home lawns. Taller grass for St. Augustine is especially important for disease resistance.
When to Call for Help
- A circular off-color patch larger than 2 feet that was not there last week
- Bermuda slow to green up when the rest of the lawn is greening normally
- St. Augustine blades with gray-brown lesions
- A cluster of small bleached spots appearing suddenly
What to Do Next
Lawn Squad of Jacksonville-St. Augustine serves Atlantic Beach, Elkton, Fernandina Beach, Jacksonville Beach, Jacksonville, Neptune Beach, Ponte Vedra Beach, Ponte Vedra, St. Augustine, and St. Johns.
Call us at 904-594-7380 or request a free quote at lawnsquad.com. Our VitaminLawn program is built for Northeast Florida’s sandy soils, warm-season grasses, and year-round growing pressure.
