Systemic Insecticide: What Is It And How Do You Use It?

Systemic insecticides have long been available for commercial use by growers to control pests and insects on ornamentals and shrubs, and their availability is on a limited basis for the homeowner.

Most homeowners use contact insecticides primarily to control insects, slugs and snails, etc. Let’s take a quick look at systemic pesticides and plants.

graphic of insects feeding on plants treated with a systemic insecticidePin

Related: Read about a Neem Oil Soil Drench Recipe.

Simply put… plants absorb the chemicals of the systemic insecticide and transport the active ingredients throughout the plant tissues.

The chemicals DO NOT harm the plant, but the plant can now fight off insect pests and invading organisms for an indefinite period.

What Is Systemic Insecticide?

Plants absorb systemic insecticides much like they absorb miracle-gro plant food. It then renders the plant’s parts, root system, stems, and leaves poisonous to invading organisms.

Some systemics remain unchanged inside the plant, and others find themselves chemically altered before they become active poisons.

A plant treated with a systemic plant insecticide no longer becomes a target for chemicals but becomes a participant in making conditions unfavorable to target pests and invaders.

Systemic pesticides (whether insecticides, fungicides, herbicides, or other pesticides) are absorbed by and transported through plants. Systemic insecticides can render some or all of a plant toxic to insects that feed on plant tissue.

How Do Systemics Enter Plants?


The chemical pesticide application reaches the internal tissues by first passing through the millions of microscopic cells forming the surface of leaves, stems, roots, or seeds, unlike insecticidal soap.

How Does Systemics Move Within Plants?

Water and food-conducting tissues are the usual pathways through which these chemicals move over long distances.

For example, soil injection or drenched soil around roots with a systemic compound shows up in the leaves and fruits. The reverse direction of movement also occurs.

Some systemic pesticides tend to move upward from the point of the insecticide application accumulating in leaf margins, growing tips, and storage organs. Others collect in underground parts.

Plants differ widely in their response to systemic chemicals. Compounds absorbed through the seed coat may kill organisms invading the seed or seedling plant.

graphic of systemic insecticides being applied to roots or injected and insects feedingPin

How Do These Compounds Work For Pest Control?

These foreign chemicals absorbed by a plant may greatly influence its balance of physiological processes.

Spray the bark of the tree trunk, and the insecticide will penetrate the bark and move into the tree. Trunk injection.

The effect may be to kill or discourage the pest as:

  • It begins to feed or enter the plant
  • It may rid the plant of an established pest
  • It may counteract poisons produced by invading fungi or bacteria
  • It may increase the natural resistance of the plant or retard the visible symptoms of the disease.

Related: How Does Neem Oil Work To Kill Plant Pests?

Does Systemics Remain Active Indefinitely?

The effectiveness generally decreases the longer the chemical remains in the plant. These causes come from:

  • Dilution of the systemic within the growing plant
  • By a breakdown of the chemical by physiological processes within the plant
  • By accumulation or congregating of the compound in certain restricted parts of the plant.

The plant’s first contact with systemic must provide the toxic level required to protect the plant from injury or the reapplied as the plant develops.

Systemic Insect Control: How To Apply These Chemicals?

The most common methods to apply systemic insecticide for trees and plants:

Insects and Problems Being Solved by Systemics

The first use of systemic insecticides proved impractical. Sodium fluoroacetate absorbed by bean plants killed insects feeding on the leaves but also left the beans too poisonous as food.

Entomologists observing aphids found they did not infest wheat grown on soils high in selenium. The chemical was too toxic for safety at the levels required for insect control.

Accordingly, the use of systemic insecticides creates a potential for ongoing toxic exposure to bees and other beneficial insects long after an application.

In the last 60 years, the introduction of a new wide range of field-tested systemic chemicals (like Imidacloprid, acephate, and dinotefuran) now control plant-feeding insects like:

In addition to killing insect pest species, these systemics, generally are noninjurious to beneficial insect predators and parasites. By using these compounds, the full advantage of biological insect control may be realized.

What Types Of Diseases Controlled By Systemics?

In recent years the introduction of systemic fungicides now combats diseases of fungus, bacterial, and virus origin as well as some deficiency troubles.

Fungus diseases controlled, or temporarily checked, include:

Bacterial diseases find themselves controlled using streptomycin preparations, including:

  • Halo blight and common blight of beans
  • Fire blight of fruit trees
  • Walnut blight
  • Bacterial spots of tomato and pepper
  • Soft rot and bacterial wilt of chrysanthemum
  • Bacterial blight of celery
  • Soft rot of philodendron

Others are being added every month.

Potentially the greatest use may be for root rots, wilts, and viruses not successfully controlled at present. 

Several chemical compounds have prevented the development of these diseases but are not being widely used because of the following:

  • Cost
  • Difficulty in application
  • Not giving protection long enough for practical control

The commonly used organic fungicides maneb, captan, and others have limited systemic activity. The antibiotics produced by living microorganisms, like streptomycin are effective for certain diseases of fungus or bacterial origin.

Another notable concern is that systemic insecticides tend to be water-soluble and prone to runoff and leaching from treated sites. 

Also, high water solubility means that a pesticide may be more easily washed into a stream or (especially in places with sandy soils) seep into groundwater.  

As a group, insecticides are perilous for insect life, including bees and other beneficial insects. 

Those insecticides designed to permeate plants from within—systemic insecticides—move through plants and may be present in all tissues after application, including pollen and nectar, posing unique risks for pollinators. 

What Are Future Prospects?

Despite problems (death of honeybees) and the “Green Movement,” future research should whittle down what appear to be insurmountable obstacles.

When we know more about the processes of absorption, movement (xylem and phloem), and storage of chemicals in tissues, the reactions of systemic compounds which result in treated plant protection without injury, the doors which now guard the widespread use of systemics may be unlocked.

Let’s be patient and wait for scientists to do their research. This should be well worth waiting for.

I always try to handle any house bug problems using a natural solution before a systemic insecticide for houseplants, systemic insecticide for aphids, tree insecticide, etc. 

In case you are not familiar with a way to take care of pest control without using health-damaging chemicals, check out:

Those are about as natural as you can get!

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