Each year I seem to have problems with my potted Victoria plum tree. A few weeks ago I noticed that scale had built up on the new branches so I set to removing them with diluted washing up liquid and a toothbrush! It now appears to be scale free. Last year when the tree had scale, all the plums dropped off before they even had a chance to grow. I have also noticed these flat 'plums' (see above) in previous years and the tree is producing them again. Any idea what they are?