Our lemons have just started to ripen, but something has started attacking them and eating through the skin. Can anyone identify what is likely doing this and what we can do to protect the other lemons on the tree?
Your lemons are being attacked by birds. Insect eggs were planted in the baby lemon epidermis, have hatched, are now larvae and the birds are going for the larvae.
Provide a large bird feeder to feed the birds. Please use a scalpel or razor blade to see if you can find the larvae. They'll look like little worms. That is what the birds are going after. Which is a cool thing to get rid of the larvae out of the fruit.
Imagine a bird sitting on the stem above this lemon. The holes are only where it is able to easily 'dig' for the larva.
Go do a bit of digging to see if there is a worm the birds will waste their time pecking at to eat in that lemon. They do not like tart citrus fruits.