By Gmpalmieri
Middlesex,
United Kingdom 
My handkerchief tree has brown blisters on its trunk which are filled with white fibrous sticky substance. These peel off easily and do not appear to be doing any damage - please does anyone know a) if they are harmful and b) if it is necessary to remove them, what is the best way of doing this?
21 May, 2010
This sounds like one of the many forms of Scale insect. Probably Mussel Scale, but without a picture it is hard to be certain. They should be brushed off with a stiff brush dipped in Horticultural soft soap (sold as Winter Protection). They can severely damage a tree if present in large numbers as they are sucking insects, like aphids. Fortunately they are relatively sedentary so except as babies they do not move around much.
21 May, 2010