On closer inspection I found that it appears to have two pests attacking it. There is a slightly sticky, shiny coating on a lot of the leaves and it is losing more leaves than normal at this time of the year. They are turning yellow and then die as they change to brown.The more easily visible pest is a very small grub or caterpillar, only about 5 mm long which I assume is eating some of the leaves. That I can deal with by spraying. The more difficult one is a very small insect, only about 1 mm long , whitish in colour and I think that is the one doing the most damage. It is not whitefly, I've seen those before when I've grown vegetables. If anyone can identify and suggest the best treatment to get rid of these pests it would be appreciated.
I've taken a few pics to show the pests, but the white one was difficult to photograph as it is so small.
I used a spray on it in the end, Yates Roseshield, and I'll repeat the treatment in a couple of weeks. I normally pick off pests from my trees by hand, but these little buggers almost can't be seen by the naked eye. 
