The majority of dollar spot cases GrassDx diagnoses from Florida submissions arrive well before homeowners in other states have even started watching for the disease, and the engine most commonly identifies them in lawns where overnight temperatures have stabilized above 50F for several consecutive weeks while irrigation scheduling still runs on late-evening cycles carried over from winter. Florida's combination of sandy low-nitrogen soils, extended dew periods, and warm winters compresses the timeline between first infection and visible turf damage to a degree that consistently surprises homeowners who moved here from northern states. Understanding the regional pattern is the difference between catching dollar spot in one or two small patches and watching it spread across a third of the lawn before it registers as a disease problem.
Dollar spot is caused by Clarireedia jacksonii (formerly classified under Sclerotinia homoeocarpa), a necrotrophic fungal pathogen that kills turf cells directly rather than living within them asymptomatically first. The fungus produces tan to straw-colored circular lesions on individual blades, typically with a reddish-brown border that distinguishes it from bleaching caused by heat or drought. The name comes from the patch size on shorter-cut turf such as bermudagrass fairways, where infections appear as silver-dollar-sized dead circles. On St. Augustine maintained at 3 to 4 inches, those patches expand to 3 to 6 inches across before they become visually obvious, which means homeowners often underestimate how far the infection has progressed when they first notice it.
Florida's climate provides near-ideal conditions for dollar spot for most of the year. The fungus requires leaf wetness periods of at least eight consecutive hours and air temperatures between 59F and 86F, with peak activity in the 70F to 80F range. University of Florida IFAS Extension documents this active temperature range specifically for Florida turf conditions. Miami and Fort Lauderdale can meet those criteria simultaneously in February. Tampa and Orlando reach consistent dollar spot risk by March. Even Jacksonville, the northernmost major city, typically hits the active window by April in most years, earlier in El Nino years with compressed winters.
Florida First-Occurrence Dates by Region: South Florida (Miami, Fort Lauderdale, Naples): late February to early March. Central Florida (Orlando, Tampa, Sarasota): mid-March to early April. North Florida (Jacksonville, Tallahassee, Gainesville): mid-April. These dates assume typical soil temperature progressions. Warm winter anomalies shift all windows two to four weeks earlier.
Dollar spot becomes active when soil temperatures at the 2-inch depth reach 60F and remains active through 80F. In South Florida, soil temps rarely drop below 60F even in January in most years, which is why the disease pressure window is effectively year-round in Miami-Dade and Broward counties. In Central Florida, soil temps cross the 60F threshold in late February on average. In Gainesville and Tallahassee, that crossing typically happens in late March.
Florida's dominant soil types, classified largely as Entisols and Spodosols, create a compounding problem that GrassDx sees reflected in the pattern of submissions from coastal counties. These sandy soils have low cation exchange capacity, meaning they hold very little nitrogen between applications. UF/IFAS Soil and Water Science notes that Florida's high-sand-content soils require more frequent, smaller nitrogen applications to maintain turf health compared to heavier soils in other regions. Nitrogen-deficient turf is significantly more susceptible to dollar spot infection because nitrogen supports the cell wall integrity and growth rate that allow grass to outpace or recover from fungal colonization. A large share of the dollar spot submissions GrassDx receives from Pinellas, Sarasota, and Collier counties involve lawns that have not received nitrogen in eight or more weeks, often because the homeowner is correctly avoiding over-fertilization but has drifted past the point where the turf can defend itself.
St. Augustine is Florida's most common residential turf grass and carries moderate susceptibility to dollar spot, particularly the Floratam variety, which dominates most of Central and South Florida. Floratam is maintained at 3 to 4 inches, and that canopy height traps moisture and slows morning drying, extending the leaf wetness window that dollar spot requires. Seville and Palmetto varieties, which are maintained slightly shorter, show somewhat lower incidence in GrassDx submissions from the same geographic areas, though both remain susceptible under high disease pressure.
Bermudagrass lawns in Florida, concentrated mostly in Central and North Florida where the turf handles the cooler winters better, show high dollar spot susceptibility particularly during spring green-up when nitrogen demand is high and the canopy is thin. GrassDx identifies the green-up period in bermudagrass, typically April in Tampa and Orlando and May in Jacksonville, as the highest-risk window for initial infection establishment. Common bermudagrass is more susceptible than hybrid varieties such as Tifway 419 or TifTuf, but all bermuda in Florida should be monitored starting in March.
Zoysia in Florida, most often Empire or Palisades variety, shows lower dollar spot susceptibility than St. Augustine or bermudagrass but is not immune. GrassDx diagnoses dollar spot on zoysia primarily in lawns with chronic low-nitrogen conditions or under tree canopies where morning dew persists past mid-morning.
Mowing Height and Dollar Spot: Cutting St. Augustine below 3 inches removes the leaf area the plant needs to photosynthesize effectively and accelerates the nitrogen deficiency that amplifies dollar spot severity. Never scalp St. Augustine below 2.5 inches during the active disease season. On bermudagrass, maintain 1 to 2 inches depending on variety and do not allow thatch to exceed 0.5 inches, as thatch harbors the inoculum between seasons.
Florida homeowners face a structural irrigation problem that other regions do not. The state's mandatory irrigation restrictions in many counties, combined with high summer evapotranspiration rates, push many homeowners toward evening or late-night watering cycles to maximize absorption. Evening irrigation is one of the most reliable dollar spot amplifiers GrassDx sees in Florida submissions. When irrigation runs at 9 PM or 10 PM, the turf surface stays wet from irrigation, then picks up atmospheric dew, and does not dry until mid-morning the next day. That creates a 10 to 12 hour leaf wetness window that is more than sufficient for dollar spot to establish new infections each night.
The corrective move is to shift all irrigation to a single pre-dawn cycle running from 4 AM to 6 AM. This allows maximum absorption before peak evapotranspiration while ensuring the turf surface dries by 9 AM or 10 AM as temperatures rise. Water utility restrictions vary by county, so check local rules before adjusting schedules, but where the window allows it, pre-dawn irrigation is the single most impactful cultural change for dollar spot management in Florida.
When dollar spot has progressed beyond early-stage cultural control, fungicide application is necessary. The three active ingredients with the strongest track record in Florida conditions are propiconazole (FRAC group 3), azoxystrobin (FRAC group 11), and thiophanate-methyl (FRAC group 1). However, documented fungicide resistance in dollar spot populations means that thiophanate-methyl alone is no longer reliable in turf that has been treated repeatedly with FRAC 1 products. GrassDx recommends rotating FRAC groups between applications any time more than two consecutive applications are needed.
Propiconazole at 1 to 2 fl oz per 1,000 sq ft applied in a minimum of 2 gallons of water per 1,000 sq ft provides reliable curative activity. Repeat on a 14-day interval for two to three applications. Azoxystrobin at 0.4 to 0.6 fl oz per 1,000 sq ft works better as a preventive, applied before symptoms appear during high-risk periods. Do not apply azoxystrobin more than twice per season in the same area without rotating to a different FRAC group, and always apply with a surfactant to improve blade penetration on St. Augustine's waxy leaf surface.
Application Tip: Apply fungicides in the early morning or evening to minimize photodegradation and avoid application when temperatures exceed 90F, which is common in Florida afternoons from June through September. Water in lightly after application only if the product label specifies it. Most contact fungicides should not be irrigated in for 24 hours post-application.
Miami and Fort Lauderdale homeowners should begin scouting for dollar spot in late January in warm years and have a preventive nitrogen application scheduled for late February at 0.5 lb actual N per 1,000 sq ft. Tampa and Orlando lawns should begin morning scouting walks in early March, with irrigation adjustments to pre-dawn cycles completed before mid-March. Sarasota and Naples fall into the South Florida window, with first-occurrence risk beginning in February. Gainesville and Tallahassee homeowners have a shorter pre-season preparation window, typically six to eight weeks between the end of dormancy and first dollar spot risk, making April the critical action month. Jacksonville homeowners should treat mid-April as the earliest meaningful risk date but should be aware that unusual warm fronts can push that to late March.
Correcting nitrogen deficiency is not just cultural background management in Florida dollar spot control. It is an active prevention strategy. Research from the University of Florida confirms that turf maintained at adequate nitrogen levels consistently shows lower dollar spot incidence than adjacent nitrogen-deficient turf under identical disease pressure. The target for St. Augustine in Florida is 3 to 5 lb of actual nitrogen per 1,000 sq ft per year, split across the growing season in applications no larger than 1 lb actual N per 1,000 sq ft. During the active dollar spot season, a light application of 0.5 lb actual N every six to eight weeks using ammonium sulfate (21-0-0) maintains turf health without pushing excess shoot growth. Ammonium sulfate also slightly acidifies Florida's often-alkaline sandy soils, which can improve overall turf nutrient uptake.
Do Not Over-Correct Nitrogen During Active Infection: Applying heavy nitrogen rates during an active dollar spot outbreak stimulates rapid, lush growth that is itself vulnerable to infection and can worsen the outbreak short-term. Target 0.5 lb actual N per 1,000 sq ft as a corrective application, not a full-rate fertilization event.
Upload a photo to GrassDx and the diagnosis engine will analyze your submission against regional Florida disease patterns, soil type data, and current weather conditions to identify exactly what you are dealing with and what to do about it.
🌿 Get a Free Diagnosis