can this be used as a patch for stuco

It could be used, however the color and texture will be different. For stucco applications, you may consider using QUIKRETE® Scratch & Brown Base Coat Stucco #113980, QUIKRETE® High Performance Cement Base Coat Stucco Mix #113956, QUIKRETE® High Performance Cement FastSetTM Stucco Patch #113976, and / or if a finish coat is needed, QUIKRETE® Finish Coat Stucco Mix - white #120180. Another option would be QUIKRETE® Pre-Mixed Stucco Patch (No. 8650), however this is an acrylic latex formulation, so a finish coat stucco cannot be placed on top of it. When making repairs, getting a color match can be difficult – we always recommend to trial the repair material in a small, inconspicuous area first and wait 24 hours to ensure that the appearance, including color, is acceptable before using the material in less discrete areas.