Plant questions

We had to delay our departure to the farm today, so we're off to the farm tomorrow in order for that "all important question" to be put to RMan :)  While I'm gone, I need to find out if anyone can help me with the following questions?

Some of my lemon tree leaves have bumps and ridges.  Is this due to a fungal / aphid infection?  Not that I can see any aphids on the trees - touch wood.


Lemon