Any ideas what these plants are suffering from??????
This pieris began to drop its leaves last year when the black powdery substance started to cover the leaves. I nurtured it ( well I thought I'd nurtured it!) and tried wiping the black stuff off but was never able to completely remove it all. I thought everything would be ok this spring but as you can see it isn't . Any ideas what it is and how I can treat it please? Thank you