Does mold grow faster on whole grain or wheat bread?

One explanation could be, that there is more sugar in white bread, than sourdough bread. Since sugar equals energy, the mold can grow faster. An other explanation could be, that it is different fungi living on the two types of bread. And even though molds are speedy little things there can, as you see, be a difference. The true molds (often white and very fluffy) being the fastest, while other types of filamentious fungi, like the green spots on the bread, is a bit slower. The green spots on the whole grain sourdough bread is often of the same genus of fungi as used to make blue cheese. So don't forget your sourdough sandwich with blue cheese or the fungus will have eaten it all before you can eat all of it! This still does not mean that you should eat bread infected with mold. There is no way you can see if it is an eatable one or one of those (many) that makes toxic compounds. Always throw moldy food away - all of it.