Imidacloprid drench for insect control.

A simple method of insect control consists of drenching the soil around a tree with a product containing imidacloprid.

The first step is to read the label.
















This product points out the need to measure the circumference of the tree 4 1/2 feet above the ground.  This hackberry tree has a circumference of 29 inches.

The second step is to apply the proper amount of product 

The directions say to add one ounce of the product per inch of tree turnk circumference to a gallon of water and use this to drench the soil around the base of the tree. 

I purchased this 40 ounce container for $30. Thus each ounce of product costs 75 cents. Treating this hackberry costs $21.75.  This treatment will provide excellent control of aphids, borers*, and gall-making insects in this tree for a full year, possibly longer. This application will also prevent lawn grubs in the area where I applied the drench around the base of the tree.

While I don't like to apply a nitrogen fertilizer to trees in the fall, many pesticides contain nitrogen to help increase the uptake of the chemical. This small amount of nitrogen (2%) in this product should not be a problem with trees or shrubs even when applied in the fall.

My next task is to spray out the grass around the base of the tree to help protect it from lawn mower and string weeder damage.

I have used the granular form of turf imidiacloprid insecticide on my lawn for grub control.  Since this treatment was made close to lilacs, virginia creeper and other woody plants, a secondary advantage of this lawn treatment was the control of insects (except Leps *) in these plants as well as in the lawn.

Be sure to read and follow the label directions.  If the product does not list vegetables or fruits,  do not use the product on those plants.

* Leps = Lepidoptera species of insects. Imidiacloprid is not an effective control of the larvae of moths or butterflies that bore into the trunk or feed on the leaves.

Hollyhock Weevils (Apion longirostre) are Bad!

Adult hollyhock weevils are often neglected until they start to cause major damage to your hollyhocks. The adults eat tiny holes in the leaves. These holes can coalesce into larger holes as the leaf expands creating an unsightly plant.

The adults are no more than 1/8th inch in length and consequently seldom seen except by those who get their noses within an inch or so of the plant. . Even then the adults may not be seen as these tiny beetles notice changes in light and movement and either hide under the leaves or drop to the ground. This pest is easy to identify as it has an exceptionally long snout as you can see in the photo.

If your hollyhocks have holes in their leaves, the problem is the Hollyhock Weevil. Hand picking this pest off the plant is next to impossible as the adults drop to the ground when the plant is disturbed. You can take advantage of this by placing a sheet under the plant and shaking the stalk. The adults will drop onto the sheet making them easier to capture and crush. Picking off the developing seed heads removes the source of the adults as the larvae feed and develop in the seeds.

A product containing the active ingredient imidacloprid and applied as a soil drench will kill the adults and larval stages. A spray of a product such as permethrin or carbaryl is also very effective. The organic insecticide pyrethrum will also work. Sprays should be avoided in the heat of the day as leaf burn can occur. We have had problems with Pyrethrum burning leaves even when it is sprayed in the evening so treat a small portion of the plant and wait a day to see if any phytotoxicity occurs. Make your additional applications based on the result of your test treatment. Always check the label to ensure the product can be used on ornamental or flowers.