Does sugar inhibit mold growth? I was reading a post earlier regarding maple syrup being left out overnight.  They were asking if their beloved Maple syrup was still safe to consume.  In the comments I believe someone brought up this question I am asking, I'm sure I could do the research and find out but hey whats the fun in that.  So here's my question does the sugar in Maple syrup or any product for that matter inhibit the growth of mold. 

Also if its true, how much sugar is needed percentage wise?

Does it matter what type of sugar?
Water activity is the big issue in preventing microorganism growth in sugary solutions.

Water Activity of Foods Table     Includes limit points for various types of bugs. A few molds will grow down to 0.60Aw.

Another foods Aw table

Water Activity of Sucrose and NaCl Solutions     From which: 180 g sucrose + 100 g water will give you a 64% sucrose solution. That'll have a water activity of 0.87, which is low enough to prevent proliferation of most bacteria, but not molds or quite, yeasts.

Oh yes, the question: A water activity below 0.8 will prevent growth of most molds, so at room temp. your syrup (Aw ~.85) will likely eventually pick up some mold, but not much in the way of bacteria.