A: St. Augustine lawns had a rough winter.
The December cold snap is the likely culprit, but not the only problem people have brought to us this spring. Whether you just have winter damage that will recover on its own with time and care, or an actual turf disease to worry about is the question. Turf disease will leave irregular patches of dead lawn, and in the case of the worst common turf disease (Take-all Root Rot), you’ll see the occasional chartreuse colored leaf blades coming out of otherwise completely dead patches in the lawn. Treat those areas with Scotts Disease Ex (azoxystrobin) turf fungicide. Peat moss raked across the worst areas would be helpful as well.
If the grass is simply sparse but is the proper green color, it’s just cold damage. Fertilize the lawn if you have not yet done so and as we head into May, keep the lawn watered and mown, and wait. The lawn should recover in sunny areas without further intervention. In areas of deep shade, the turf may have completely collapsed. Limb up and properly thin out the canopy of trees throwing heavy shade over those areas before trying to lay new sod, or consider putting in beds of ground covers, many of which are more shade tolerant than any turfgrass.