Root rot

I have been having problems with root rot does anyone know what you can treat it with to stop it.It hit my last sang patch hard.

Ridomil

Thanks where can you buy it at.

Landmark or any place that sells farm seed and or fertilizer etc.
It comes in 50 # bags and usuall runs $250-300.00 a bag. Mix with sand to give it a lift. Apply dry before a good rain and the rain takes it down into the ground.