Didn't Think Italian Cypress Got Borers. I Was Wrong!

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.

This formulation of imidacloprid (this name is found under ingredients) is probably the most common one found on shelves. Shop around because there may be some that are less expensive. Compare the percentage of imidacloprid on the label with the price of products. Higher percentages single just means you get more "bang for the buck".

            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.

Excerpt from the product label of Imidacloprid 2F manufactured by Prime Source LLC. The active ingredient is available from several manufacturers so it is imperative to read the product label before making any applications.

            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.

            I am not sure why you are using a surfactant unless it is to help this insecticide drench move into the soil faster after drenching the area. Surfactants are a very broad category of  spray additives but usually used to move liquid fertilizers, insecticides and fungicides inside plant leaves when they are sprayed.

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.