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How to Do a Systemic Insecticide Root Drench

By DoMyOwn staff

A systemic root drench application of an insecticide offers long-lasting prevention and treatment to protect your ornamental shrubs and trees from damage from sucking insects such as aphids, mealybugs, scale, emerald ash borers, and others.

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Video Transcript

Hi I'm Kayla with DoMyOwn.com and today we're going to talk about a systemic insecticide root drench. A systemic insecticide root drench is pouring a concentrated insecticide over the mineral soil of an ornamental plant such as a tree or a shrub to control sucking pests like aphids, emerald ash borers scale, mealy bugs, and a few others.

It's very important to be sure that you properly identify the pest that you're treating before doing the application. This treatment will translocate up the roots of the plant systemically to provide complete long-term prevention and control, different than a full year application that will provide faster results but won't last as long. For prevention, a systemic insecticide soil drench would be the best option and should be done before a foliar application. For an active infestation, you would want to do a soil drench as well.

As a full year application, smaller trees are normally treated in the spring after petal fall bigger trees can be treated in the fall that way they're ready for new growth in the spring. This type of application is meant for ornamental plants. It is not meant for edible species, linden, or tilia species.

Here's what you'll need to do this type of application: a measuring tape, a watering can or bucket, the insecticide of your choosing, the proper PPE like gloves, long sleeves, pants, closed-toed shoes, and water.

This treatment is measured with DBH. DBH stands for diameter at breast height or trunk diameter for trees and height for shrubs and trees that do not have a trunk to measure.

  • You should measure up the trunk until you get to 48 inches in height. Make sure to mark the 48 inch point on the tree. In this case, we marked it with a piece of black tape.
  • Then, at that point, measure the circumference of the tree using a measuring tape.
  • You should then divide the tree circumference by pi 3.14
  • the DBH will be rounded up from the number you get.
  • If it is a multi-trunk tree, you measure each trunk and add them together


Some products will give rates by tree circumference rather than diameter. Make sure you read the application label of any product you are using carefully to ensure you are applying properly.

To perform this type of treatment, you will measure the amount of water and insecticide per the product label and combine in a bucket or a watering can. Normally, the dilution is done with a small amount of insecticide and a large amount of water. The size of the plant is the main factor as to how much water an insecticide to use. Make sure there is nothing around the base of the tree that would prohibit the insecticide from getting to the roots such as mulch or dead leaves.

Apply to the base of the tree in the root zone to the mineral soil only pour on the ground not on the trunk or it won't be effective. The main two active ingredients you would use for this type of application would be imidacloprid or dinotefuron- those are the two we normally recommend. Imidacloprid products would be used at 0.1 to 0.2 ounces generally per inch of trunk diameter and last a year.

Be sure that you're reviewing the product label for complete application instructions but generally you're going to be using about a pint of water per inch of trunk diameter at minimum. You can start to see results in a couple of days but sometimes it can take up to eight weeks for the systemics to translocate up the plants.

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