Apple powdery mildew
Yes Sulfur is a big problem.
There is another material you can try.
Immunox by Spectracide.
Be sure you use the right formulation since Spectracide market several different materials and mixes under the same Immunox name.
Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate
Benomyl was removed by the manufacturer several years ago.
That class of fungicide was effective but the fungi developed resistance rather quickly.