How to remove black spots from White Plastic Deck Furniture?

Spray paint would probably be your best option if you have tried cleaning them and the spots don't come off.

Try cleaning them with simple green.If they still do not come clean you can spray paint them with Rustoleums 2X spray paint for plastic

Maybe vinegar and water? Have you tried using a cleaning brush? Vinegar can clean just about anything lol.

Krylon Fusion spray paint. Will adhere to the table and be easier to maintain. No sanding or priming necessary.

Here is one article I found that hopefully will help you :) http://homeguides.sfgate.com/clean-deep-stains-white-plastic-furniture-94707.html, good luck

I got a mold and mildew solution from walmart and wowser easy to wipe off