I live in Louisiana, and recently early in the mornings I have noticed what looks like someone drug an oil can thru lines in my grass. Upon closer looking, and touching- it is only on the surface. When touched it feels like a silk feeling. No damage to grass, washes away in rain...but I thought it could be a fungus of some kind. Since we are in extremely humid area. Does anyone know what it could be. Does not grow back after cutting grass, or once pulled off. Has me stumped.