Mold forming on underside of bed cover

I have mold forming on the underside of my Lund soft vinyl folding bed cover. How can it be cleaned or prevented without damaging the out side surface? The vehicle is stored outside in Florida.

 

EDIT
Mold forms in the dark. It'll be tough to control something like that. However, you can remove the cover, put on some latex gloves, scrub it with dish soap and water. Spray Lysol after to kill bacteria and allow to dry in an area with light. To prevent it from happening again, keep a routine cleaning of the cover. I used to work for a cleaning company a while back and have a good understanding of mold removal and sanitizing. Hope this helps.

 

Vinegar works pretty well too and is a bit less aggressive than Clorox can be

 

Sounds to me like your cover might be condensateing on the underside or you have water leaking into the bed and not being able to dry. Mold only forms where there is water. Darkness just accelerates the process.