Borer and your citrus tree.
We are often asked how and when to prune citrus trees in Auckland to how protect them from borer.
Pruning should be done after the main fruiting period in late winter to early spring so the wounds can heal before the beetle’s fly and have an opportunity to lay their eggs in freshly cut wood.
Fruit should be harvested with secateurs rather than just them pulling off. This way you can prune as you pick!
Fruit is produced on new seasons wood so pruning encourages more fruit.
Borer gets in through wounds as the adults lay their eggs during the flying season (around November to March) and the larvae do all the damage. They tunnel their way inside the branches towards the stem preventing sap flowing, and therefore nutrients and water from being transported through the limbs and to the leaves. They can take 2-4 years before emerging as a beetle and can cause a lot of damage over that time.
If you find evidence of borer, remove the limb immediately where possible right to the parent stem, treat the holes with a borer insecticide, and monitor the tree. Be mindful that an infested tree can be a breeding ground for other trees to be infested too and sometimes its better for your garden or orchard to sacrifice one tree to save others being damaged too.
A heavy infestation can kill the tree.