Whats happening to my apple tree leaves? What should I do?

My little apple tree was doing really well until a couple of weeks ago. I noticed one or two leaves which had squiggly brown lines on them, and the leaves are gradually going brown on the edges. Now I have noticed the majority of the leaves have the same as if whatever it is has spread. What can I do?

 

It's leaf miner.
If the tree is small I'd just go round and squash the bug inside the leaves.
The bugs can be seen at the end of the trail in the leaves.

 

Brilliant! thank you. ( what a horrible thought!) but thanks anyway.
Dont go anywhere, Ive got a ton more questions! Ive been renovating my garden. Things were going well at initially, but then in the past few weeks have noticed lots of various leaf damage, and plants appearing to be suffering.

 

Job done!

Now for my ceanothus . I planted it a couple of months ago in the hope for it to fill a space by the fence. It took really well and was doing great doubling in size, but Ive recently inspected it to find that its dying ( lost leaves and drying up /dying at the back) what could be troubling it, any advice?
As you can see from the photo of the back of the shrub, its virtually disappeared, it was a full green luscious shrub before.

 

The ceonothus looks ok to me, probably just stressed from growing and the dry summer. Keep it well watered till the end of the summer.

 

Thanks again Redwing. Will do