Are Systemic Insecticides The Future Of Pest Control?

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The development of systemic pesticides for commercial use is progressing rapidly. These are chemicals that can be absorbed by a plant and transported throughout its tissues in an active form. They are non-harmful to the plant and can provide long-lasting protection against invading organisms.

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This dream has become a reality, as a select few of these compounds have been introduced commercially after undergoing intensive screening by research laboratories.

Questions About Systemic Pesticides

In anticipation that someday you will be using systemic pesticides, you would probably want to know the following: 

1. What is a Systemic Pesticide? 

A systemic pesticide is a chemical that is absorbed into a plant’s system and renders its roots, stems, and leaves poisonous to invading organisms.

Some systems within the plant remain unchanged, while others are chemically altered before becoming active poisons.

When a plant is treated with a systemic pesticide, it becomes an active participant in creating unfavorable conditions for invaders. 

2. How do Systemic Pesticides Enter Plants?

Systemic pesticides enter plants by passing through millions of microscopic cells that make up the surface of leaves, stems, roots, or seeds.

3. How Do Systemic Insecticides Move Within A Plant?

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

For example, if the soil around the roots is treated with a systemic compound, the chemical will eventually appear in the leaves or fruits of the plant.

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

It’s important to note that plants differ widely in their response to systemic chemicals, and compounds absorbed through the seed coat may kill organisms invading the seed or plant.

4. How Do These Systemic Compounds Work?

When a plant absorbs foreign chemicals, it can greatly influence its balance of physiological processes. The effect of these chemicals may be to kill or discourage pests as they begin to feed or enter the plant.

Alternatively, they may rid the plant of an established pest, counteract poisons produced by invading fungi or bacteria, increase the plant’s natural resistance, or retard the visible symptoms of the disease.

5. Do Systemics Remain Active Indefinitely?

No, the effectiveness of systemic compounds generally decreases the longer they are in the plant. This may be due to dilution of the compound within the growing plant, breakdown of the chemical through physiological processes, or accumulation or congregating of the compound in certain restricted parts of the plant.

Therefore, the first contact of the plant with the systemic must provide the toxic level required to protect the plant from injury, or the chemical must be renewed as the plant develops.

6. How Are These Systemic Chemicals Applied?

The most common methods for applying systemic pesticides are by spraying the leaves, drenching the soil, and treating the seeds. Granular pesticides are also available. In addition, chemicals have been injected into the trunk or stem of plants or applied as a paste to the outside.

7. Systemics Are Solving Insect and Mite Problems

The first use of systemic insecticides was impractical. When sodium fluoroacetate was absorbed by bean plants, it killed insects that fed on the leaves but also left the beans too poisonous to be used as food.

Entomologists observed that aphids did not infest wheat grown on soils high in selenium, but this chemical was too toxic for safety at the levels required for insect control.

However, in the past few decades, a new range of organic chemicals has been discovered and field-tested for controlling plant-feeding insects.

In Europe, systemic insecticides applied to the foliage have been used to control aphids infesting garden peas and sugar beets.

In the United States, systemics can control mites, aphids, and leafminers infesting apple and pear trees and aphids infesting lettuce, cabbage, strawberry, and pecan trees.

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

8. What Types of Diseases May Be Controlled By Systemic Applications?

Recently, systemic fungicides (commonly referred to as chemotherapeutics by scientists) have been effectively used to combat diseases caused by fungi, bacteria, and viruses, as well as certain deficiency problems.

Fungus diseases are controlled or temporarily checked, including:

  • Dutch elm disease
  • Oak wilt
  • Fusarium and verticillium wilts of certain plants
  • Rhizoctonia root rots
  • Strawberry red stele
  • A chocolate spot of the bean
  • Black grape rot
  • Early blight of tomato
  • Bleeding canker of various trees
  • Cherry leaf spot
  • Damping-off of plants
  • Some diseases of turf

Bacterial diseases which have been controlled using streptomycin preparations include:

  • Halo blight and common blight of beans
  • Fire blight of fruit trees
  • Walnut blight
  • A bacterial spot of tomato and pepper
  • Soft rot and black leg of potato
  • Bacterial wilt of chrysanthemum
  • Bacterial blight of celery
  • Soft rot of philodendron

Others are being added every month.

X-disease (a viral disease), which affects peaches and other stone fruits, can be controlled by a systemic virus disease. The greatest potential for systemic fungicides may be for root rots, wilts, and viruses that other means cannot effectively control.

While several chemicals have been found to prevent the development of these diseases, they are not widely used due to their cost, difficulty in application, or inability to provide long-lasting protection for reasonable control.

Commonly used organic fungicides such as maneb, verbatim, captan, bam, organic mercury compounds, and disclose have limited systemic activity.

However, antibiotics produced by living microorganisms such as streptomycin, and aureomycin have proven effective for certain fungus or bacterial origin diseases.

Many complex organic chemicals, particularly oxyquinoline salts, have also been effective and are sold under various trade names.

What Is The Future Prospects of Systemics In Plant Production?

Although there are challenges, future research should aim to overcome what may seem like insurmountable obstacles.

As we gain a better understanding of the processes involved in the absorption, movement, and storage of chemicals in plant tissues, as well as the reactions of systemic compounds that result in plant protection without causing harm, we may be able to unlock the doors that currently limit the widespread use of systemic pesticides.

It’s important to be patient and allow scientists to conduct their research. The potential benefits of this work could be significant and well worth the wait.

44659 by Malcolm C. Shurtleff And E. T. Hibbs