Brown Grass Veins (cat, spring, south, pets)

[hou-iah]

I seem to be getting veins and spots of dead grass and wondering if anyone can diagnose whether its disease, fungus, thatch, or some other ailment on my southern St. Augustine Lawn.

No pets although the neighbor's cat sometimes makes an appearance.

[Hemlock140]

There are several possibilities based on your photo.

Uneven application of fertilizer
Moles or gophers tunneling and disturbing the roots underneath
Dogs peeing on the lawn
Grubs or Crane Fly Larvae eating the roots
Your variety gets some common fungal diseases, especially as the late spring temperatures rise to 60-65F

One thing you can try is dumping a bucket of soapy water in one spot that shows brown, and watch over the next 1/2 hour to see if any creatures come up to the surface.