A pieris japnioca in my back garden has some dead areas this season. It's had spider mites since I moved into my east Vancouver house 5 years ago. Maybe the mites have taken their toll? In spring the troubled plant usually has chartreuse leaves and has done well despite the spider motes till this year. It's right beside another flourishing pieris (with new leaves that are red) that also has spider mites. Both are quite large and I have not known how to effectively treat the mites ....Any suggestions?