AusBonsai

I have notice for some time now that my cumquat has been fading in vigour I weeded and sifted through the top soil to find these guys. firstly…
What are they?
will they be right through the soil?
Should I repot to eradicate or can I add something that will knock them off?

not really bonsai material but possible literati style in the future...

#1 is a grass eating caterpillar and I don't think it will be doing anything to your tree.
#2 WILL be doing harm. It is a cockchafer grub aka curl grub. They live in the soil and eat roots. I'd use a systemic insecticide like Confidor. Spray on the leaves and soak it into the soil as well.
#3 is some sort of moth cocoon. possibly the same species as #1 but many look alike so hard to tell. At this stage you probably cannot kill it with insecticide because it is not eating and protected by the shell.

Note that citrus trees are quite hard to keep healthy in pots. They need plenty of feed and water to do well. The cockchafers are probably doing some harm but the tree may have other problems contributing to decline. Treat for the bugs and see if it comes good.

Thank you will apply tomorrow and