Mechanical Control of Borers in Fruit Trees

I will usually take a very sharp, large knife and remove this loose bark and find out how much damage has been done by the borer.
No one talks about this subject probably because no one has really tried it much in the past. Borer problems in fruit trees in Las Vegas are usually from two different possible insects; flat-headed apple tree borer or the Pacific flatheaded borer. The damage from both of these insects are very similar. They usually damage areas of the tree damaged by intense sunlight. This means the upper surfaces of limbs and the sides of limbs facing south or west.

Early damage from borers starts with this brown crystalline sap coming from damaged branches. When it rains this sap gets very gooey like petroleum jelly. This is peach but the limbs have been whitewashed.

More borer damage on the same tree.

Damage does not usually cause limb dieback unless the limb is small or the problem has been developing in the tree for a couple of years. With repeat attacks the limb becomes weaker, the vascular system that carries water and nutrients is severely impeded and then we see branch dieback and flagging (leaves dead on the tree without falling off).

When damage from borers has been going on for quite some time the lifting of the bark can be extensive and damage can extend nearly all the way around the limb.

I will usually take a very sharp, large knife (not a pen knife, this would be dangerous) remove this loose bark and find out how much damage has been done by the borer. If the damage has not extended over half way around the limb I will remove the bark all the way down to fresh wood.

The dead wood and bark is completely removed from the limb and the limb is allowed to heal. Nothing is applied to the limb but time.

In our many years of doing this in the orchard I would estimate that over 50% (very conservative estimate and it is probably closer to 80%) recover with this method. I can only guess but removing the loose bark takes away any hiding places the adult will have when it exits the tree, if it does.  If successful, the tree heals over the wound in two to three years.

Peach tree borer repair with a knife and healing of the upper surface of the limbs.