I too have a madarin that has never done well in its first home and moved it a few months ago to a sunnier spot. It seemed to do quite well at first but now has yellowing leaves and on closer inspection found small black scabs or bumps on the twigs -- quite a lot of them. Is this scale? I read something that said I shouldn't use oil spray in hot weather. Any suggestions would be appreciated. I've never had fruit from this tree!