How do I treat borer in my lemon tree?

Lemon tree borer is a NZ native insect that flies at night in spring and summer and has a wide variety of hosts, including citrus. Some trees will continue growing, flowering and fruiting but over time the trees vigour is reduced. You can tell if the borer are still active as there will be fresh ‘frass’ or sawdust on and around the tree. As the larvae or worm that does the damage is inside the plant, it is very hard to control and spraying with a control product isn't effective. There are a few things that can be done to help protect and treat the tree:

• When pruning, make sure cuts are clean and the branches aren’t bruised - broken bark gives an entry point to the adult to lay its eggs.
• Paint pruning cuts with a water based paint or pruning paste to seal the wound.
• The damaged part of the tree can be cut back to below the borer damage, however only do this if it’s practical to do so. It depends on how well established the tree is. Make sure any wounds are sealed with a water based paint or pruning paste.
• Put thin wire into the holes to see if you can skewer the grub.
• Borer control products can be squirted into the holes or the holes sealed with grease or Vaseline.