This is the epitome of poor EIFS construction and I hope that both the applicator and builder were sued into oblivion. For starters, yes that black mass is mold, and black mold may or may not be toxic. As you can see, the mold originates where moisture is commonly a problem — around the window. What the common home owner will not notice about the EIFS installation is this:

1. There is no moisture barrier to keep the water off the substrate, which is there the mold would grow. Any water that gets behind the EIFS barrier is going to create the perfect environment for mold growth
2. The substrate is plywood, which is currently not recommended by EIFS manufacturers
3. Those white stripes are channels of adhesive, using a 3/8″ notched trowel. The channels were actually installed in a HORIZONTAL pattern, trapping any water that tried to run down the substrate (where it shouldn’t be anyways). This installation is beyond stupid and makes me feel like Gordon Ramsey.

Just to clarify however, modern EIFS (when correctly installed) would not use wood as a substrate, would have a moisture/weather barrier over the substrate, and is installed with VERTICAL channels of adhesive, allowing water to run down the wall and not become trapped. These problems are by no means on every EIFS application, modern exterior insulation finish systems have corrected these problems, but is not uncommon in older installations with poor applicator training.