Q.Geraniums
The geranium leaves are going yellow and are being eaten by a bug. They are still flowering. It is autumn here in Australia. Should I prune them back? We do not get frosts in winter so they winter over outdoors. Some are in pots and some in the ground.

Yellowing leaves can be due to a few different issues.
Check the link below and make the necessary corrections.
https://www.gardeningknowhow.com/ornamental/flowers/geranium/geranium-yellow-leaves.htm