Q. I have a fruit bearing
plum tree approximately 2 years old. I noticed an amber hard substance on the
trunk. I think it’s borers. If it is, what can I do to save it and still be
able to eat the fruit?
This insecticide is distributed everywhere (systemic) inside
the tree and lasts for nearly 12 months. And yes, it is labeled for fruit trees
that are bearing fruit as well as vegetables. This pesticide applied to food
bearing crops makes me nervous for obvious reasons.
plum tree approximately 2 years old. I noticed an amber hard substance on the
trunk. I think it’s borers. If it is, what can I do to save it and still be
able to eat the fruit?
A. The most effective way
to kill borers is to apply a systemic pesticide and let the tree distribute
this pesticide everywhere inside it. There is a very popular systemic
insecticide available nearly 100% effective at killing borers if they are
present.
to kill borers is to apply a systemic pesticide and let the tree distribute
this pesticide everywhere inside it. There is a very popular systemic
insecticide available nearly 100% effective at killing borers if they are
present.
This insecticide is distributed everywhere (systemic) insidethe tree and lasts for nearly 12 months. And yes, it is labeled for fruit trees
that are bearing fruit as well as vegetables. This pesticide applied to food
bearing crops makes me nervous for obvious reasons.
Let me present to you an idea that does not require
pesticides but a little work on your part. I have observed it to be about 80%
effective. This requires a sharp knife and a method to sanitize it such as
alcohol, butane lighter or even Pine-Sol.
pesticides but a little work on your part. I have observed it to be about 80%
effective. This requires a sharp knife and a method to sanitize it such as
alcohol, butane lighter or even Pine-Sol.
 |
| Plum sap from a pruning cut in the spring |
 |
| Sap oozing from the trunk of a fruit tree due to overwatering |
Plums are very sappy trees. Any injury to living parts of
the tree cause sap to be produced. The production of sap is a defense mechanism
against “intruders”. The tree does not differentiate between damage from boring
insects and damage caused by pruning, invading diseases or environmental damage.
the tree cause sap to be produced. The production of sap is a defense mechanism
against “intruders”. The tree does not differentiate between damage from boring
insects and damage caused by pruning, invading diseases or environmental damage.
 |
| Extensive damage to the trunk of plum and bark is peeling from the west side |
To a plum tree, it’s all the same. It reacts by producing
sap. If it is an intruding insect like a borer, sap engulfs and frequently
suffocates it. If the damage by boring insects is extensive, loose bark easily
lifts away from the damaged area because that area is dead.
sap. If it is an intruding insect like a borer, sap engulfs and frequently
suffocates it. If the damage by boring insects is extensive, loose bark easily
lifts away from the damaged area because that area is dead.
 |
| Borer damage under the bark leaving behind “debris” in the tunnels just under the bark from eating |
Damage from boring insects most first appears on the west
or south facing sides of the trunk and limbs or on their upper surfaces. A tree
may have damage for one or two seasons before you see parts of it suffering
outwardly. On plums, sap is a good indicator something is going on.
or south facing sides of the trunk and limbs or on their upper surfaces. A tree
may have damage for one or two seasons before you see parts of it suffering
outwardly. On plums, sap is a good indicator something is going on.
The only way to find out if a boring insect is involved is
to inspect the wood under the sap for damage. It is easiest to do this after
the leaves drop in December. You can wait. It’s cold now and they are not
active.
to inspect the wood under the sap for damage. It is easiest to do this after
the leaves drop in December. You can wait. It’s cold now and they are not
active.
When you are ready, take a very sharp, sanitized knife
and remove the sap along with the bark just under it. Look for damage to the
trunk or limbs in the exposed wood. Boring insects leave debris from feeding, in
tunnels, just under the bark.
and remove the sap along with the bark just under it. Look for damage to the
trunk or limbs in the exposed wood. Boring insects leave debris from feeding, in
tunnels, just under the bark.
 |
| Borer damage removal using a sharp knife removing all the damaged bark to fresh wood |
If you do not see damage to the wood under the sap, then
this damage is not due to borers. Leave it alone if the limb appears otherwise
healthy. If you see insect damage in the wood under the bark, cut and remove
ALL bark from the damaged area with your sharp knife and let it heal on its own.
If the damage is extensive and the limb is weak, remove it.
this damage is not due to borers. Leave it alone if the limb appears otherwise
healthy. If you see insect damage in the wood under the bark, cut and remove
ALL bark from the damaged area with your sharp knife and let it heal on its own.
If the damage is extensive and the limb is weak, remove it.
There is no pesticide you can apply to the tree that will
kill the borers AND leave the fruit safe to eat in my opinion even if it’s on
the label and you can use it for that purpose.
kill the borers AND leave the fruit safe to eat in my opinion even if it’s on
the label and you can use it for that purpose.