GaN/AlN quantum dots (QDs) were grown by the Stranski-Krastanov method on Si(111). The thermal expansion coefficient mismatch between the Si substrate and GaN/AlN film leads to an additional biaxial tensile stress of 20-30 kbar in the III-nitride film, which we have selectively modified by etching a cross-hatched pattern into the as-grown sample. The results show that a suitable choice of stripe orientation and width from ~2 to 10 mum can create regions of in-plane uniaxial stress that enable a selective and local control of the polarized luminescence from ensembles of QDs which were probed with cathodoluminescence.