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.

Hackberry leaf spots may be insect caused.

Hackberry (Celtis spp.) leaves often have spots on the upper surface that looks somewhat like measles or blisters but are light green or yellow in color.


These spots are caused by the Hackberry Blistergall maker (Pachypsylla celtidisvesicula). The blisters are 3 to 4 mm in diameter and only slightly raised from the leaf surface.

There are 25 millimeters (mm) in an inch so these spots are quite small.

When you flip the leaf over you will see and can feel many tiny bumps. The feeding activity of this psyllid stimulates the tissue into forming a gall, an abnormal growth.

[Pysyllids are  known as jumping plant lice due to their tendency to jump when disturbed.]

You may find blistergall makers and nipplegall makers on the same leaf as is seen in the next photograph.  The nipple-like galls are due to the feeding activity of Pachypsylla celidismamma.

 Note the three nipple galls mixed in with the galls of  the hackberry blistergall maker.

Psyllids feed by inserting their mouth parts into the phloem of the tissue and sucking out the plant's juices.  They tend to feed on either a single type of plant such as the hackberry or members of the same family of plants.  Consequently you do not have to worry about these insects feeding on any plants other than hackberries.

There is one generation of these gall makers per year with the eggs being laid as the leaves unfurl in the spring.  A dormant or horticultural oil applied to the tree to coat the overwintering adults helps control this insect.  The use of a product containing the insecticide imidacloprid this fall will solve next spring's hackberry psyllid problems.

While this insect is more cosmetic than damaging, one can easily see why homeowners are concerned when they have an infestation of these leaf-disfiguring insects on their hackberry trees.

To learn more about psyllids check out the Psyllid web site.