How Can I Clean Mildew Off My Bike Trailer?

We packed away our Burley bike trailer in our boat over the winter. There was water left in the bottom of the boat before they put it in storage. The water sat there all winter with the Burley inside it under a cover.

There is so much mildew on it I don't know if I can get it off. I'm not sure exactly what type of fabric it is, but it is the same as every Burley or bike trailer. Please help.

By Jen from Otsego, MN