Q. I had a lot of borer damage to my trees so last summer
I cut out most of the large branches and reduced the height of the trees to
about 10 feet and let them grow back. Then I treated the soil with an
insecticide, surfactant and fertilizer. That was my counterattack regarding the
borers.
Borer exit holes in the trunk of Italian Cypress sent in by an alert reader. |
A. Make sure trees that you do cut back will grow back.
Some trees like most ash trees will not grow back very well if they are pruned
severely. Also make sure the pruning instruments are all sanitized before
pruning.
Insecticides
like Imidacloprid (active ingredient) used as a soil drench (mixed with water
and contained on the surface of the soil above the roots) are systemic and
taken up by roots of the tree and kill many types of borers. Whatever
insecticide you use should be systemic and have a label that says it is
effective against wood boring insects.
If the insecticide
has “staying power” inside the tree then I would apply it after the tree
flowers. This is usually in early spring. Long-lasting, systemic insecticides
like Imidacloprid are suspected to harm honeybees. There is a possibility the
insecticide could be available to honeybees if it is applied just before
flowering.
A portion of the product label for Imidacloprid 2F warning about killing honeybees. Be careful when you spray insecticides or apply them as a drench to the soil. |
One example of a surfactant. When mixed with a spray it helps the product get inside leaves or stems. When mixed with a liquid drench it might help the drench move into the soil better. |
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