Organochlorine insecticides

Organochlorine insecticides are a group of chemical compounds containing chlorine atoms in their molecules, which are actively used for protecting plants from various pests. These substances are highly toxic to insects, blocking key physiological processes, leading to their death. Examples of organochlorine insecticides include substances such as ddt (dichlorodiphenyltrichloroethane), aldrin, and chlordane. While organochlorine insecticides were once widely used, their application is now restricted or banned in most countries due to their toxicity and long-term impact on the ecosystem.

Goals and importance of use in agriculture and horticulture

The goal of using organochlorine insecticides is to effectively control pest populations that can cause significant losses in agriculture and horticulture. These insecticides are particularly effective against a wide range of insect pests, such as flies, mosquitoes, beetles, and mites. They provide high efficiency over an extended period, making them attractive for combating pests in agricultural crops such as cereals, vegetables, and fruits. In horticulture, organochlorine insecticides are used to protect ornamental plants and trees from pests.

Relevance of the topic (why it is important to study and apply insecticides correctly)

The study and correct application of organochlorine insecticides are crucial for maintaining ecological balance and plant health. Improper use of insecticides can lead to the development of resistance in pests, as well as destruction of ecosystems, including beneficial insects and even animals. Understanding their mechanisms of action, correct application methods, and potential risks helps minimize negative consequences for nature and human health, making this topic relevant for agronomists, gardeners, and environmental specialists.

History of organochlorine insecticides

Organochlorine insecticides (ocis) have played an important role in the history of pest control and agriculture, significantly contributing to increased crop yields and public health during the mid-20th century. These insecticides are based on chemical compounds containing chlorine, carbon, and hydrogen, and were initially developed in the early 20th century. However, their widespread use has been associated with environmental issues and toxicological risks, leading to restrictions and bans on the use of many of these substances in various countries worldwide.

1. Early discoveries and developments

The history of organochlorine insecticides begins in the late 19th and early 20th centuries, when scientists began to explore the potential use of chlorinated hydrocarbons for pest control. In 1939, swiss chemist paul müller discovered the insecticidal properties of ddt (dichlorodiphenyltrichloroethane), which was a groundbreaking discovery that shaped the future of pest control. Ddt became the first widely used organochlorine insecticide, demonstrating high effectiveness against a wide range of insects, including mosquitoes, lice, and agricultural pests. It gained widespread use during world war ii, where it was used to combat disease-transmitting insects and protect soldiers from malaria.

2. Widespread use in agriculture

After world war ii, the use of ddt rapidly expanded in agriculture worldwide. Following its success, other organochlorine insecticides were developed, such as aldrin, dieldrin, heptachlor, and chlordane. These insecticides were highly effective in pest control and provided long-term protection, making them popular in agriculture. They were used to combat pests on various crops, including cotton, tobacco, vegetables, and fruits. Organochlorine insecticides also found application in controlling household pests, such as termites, ants, and cockroaches.

3. Safety and environmental issues

Despite their effectiveness, the use of organochlorine insecticides led to new ecological and toxicological problems. These substances were highly toxic not only to insects but also to other organisms, including beneficial insects such as bees and animals. The durability and ability of organochlorine insecticides to accumulate in ecosystems, contaminating soil and water, became serious issues. Biomagnification—accumulation of toxins in food chains—also occurred, leading to significant ecological consequences. Due to these problems, many of these insecticides were subjected to restrictions or bans in several countries starting in the late 1970s.

4. Modern approaches and issues

Today, organochlorine insecticides remain in use, but their application is limited due to strict environmental standards and safety concerns. The development of resistance in insects to these insecticides and their decreased effectiveness have become major problems in modern chemical plant protection. In response to these challenges, scientists and agronomists are actively developing new strategies and formulations, combining organochlorine insecticides with other control methods, such as biological control and mechanical methods.

Thus, the history of organochlorine insecticides is a journey from revolutionary discoveries and widespread use to the recognition of environmental and toxicological risks, which has led to the search for safer and more sustainable plant protection methods.

Organochlorine insecticides: classification

1. By chemical structure

Organochlorine insecticides can be classified by their chemical structure, which determines their physicochemical properties and activity against various pests:

• Aromatic organochlorine compounds: these chemicals contain a benzene ring with chlorine atoms. An example is ddt (dichlorodiphenyltrichloroethane), one of the most well-known and widely used organochlorine compounds, although its use is highly restricted due to environmental consequences.
• Acyclic organochlorine compounds: these compounds do not contain an aromatic ring and have a linear or branched structure. An example is hexachlorocyclohexane (hch), which was used for protecting agricultural crops from various pests.
• Chlorinated hydrocarbons: these include chemicals containing carbon chains attached to chlorine atoms. An example is chlorobenzene.

2. By mechanism of action

Organochlorine insecticides can be classified based on the type of impact they have on the insect's body. Their primary mechanism of action involves blocking the insect’s nervous system:

• Insecticides affecting sodium channels: these substances disrupt the normal function of sodium channels in the insect’s nervous system, leading to paralysis and death. An example is ddt.
• Insecticides that block acetylcholinesterase: these chemicals block the enzyme acetylcholinesterase, which plays an important role in nerve impulse transmission, leading to disrupted nerve transmission and insect death. An example is chlorpyrifos.

3. By application area

Organochlorine insecticides can be classified according to their area of application:

• Agricultural insecticides: organochlorine compounds are widely used in agriculture to protect crops from pests such as aphids, flies, beetles, and other insects. Examples: ddt, hexachlorocyclohexane (hch).
• Household insecticides: organochlorine insecticides are also widely used for controlling household pests such as cockroaches, flies, and mosquitoes. Example: cypermethrin.

4. By toxicity

The toxicity of organochlorine insecticides can vary depending on their chemical structure and method of application:

• Highly toxic products: these insecticides are highly toxic and are used against pests that cause significant damage. For example, ddt has high toxicity, which limits its use in agriculture and households.
• Moderately toxic products: medium-toxicity organochlorine insecticides include chlorpyrifos, which is widely used for protecting crops.
• Low-toxicity products: some organochlorine insecticides have relatively low toxicity and are used when a safer option is needed. Example: permethrin.

5. By duration of action

Organochlorine insecticides can be divided into products with varying durations of action:

• Long-lasting insecticides: these substances continue to affect pests for a long time after application. An example is hch, which could persist in the environment for an extended period.
• Short-acting insecticides: these products act quickly, but their effects wear off quickly. Example: pyrethroids, which act quickly but do not remain in the environment for long.

6. By environmental stability

Organochlorine insecticides can be classified based on their stability and degradation in the environment:

• Photostable products: these substances maintain their activity in sunlight. Example: ddt.
• Photounstable products: these substances break down quickly when exposed to sunlight, limiting their use in open spaces. Example: hexachlorocyclohexane (hch).

Mechanism of action

How insecticides affect the nervous system of insects

• Organochlorine insecticides affect the nervous system of insects by disrupting the normal transmission of nerve impulses. This is achieved by blocking acetylcholinesterase, the enzyme that normally breaks down the neurotransmitter acetylcholine after its action on nerve cells. As a result, acetylcholine continues to act on nerve endings, leading to hyperstimulation of the nervous system, paralysis, and ultimately, the insect’s death.

Effect on insect metabolism

• Organochlorine insecticides also affect the metabolism of insects, preventing the normal regulation of their life processes. This disrupts the balance of substances in cells, reduces energy exchange, and impairs the insects' ability to reproduce and survive.

Examples of molecular mechanisms of action

1. Effect on acetylcholinesterase: organochlorine insecticides inhibit acetylcholinesterase, leading to an accumulation of acetylcholine in synaptic clefts and causing paralysis.
2. Effect on sodium channels: they also interfere with the functioning of sodium channels in nerve cells, causing their constant opening, which results in an uncontrolled flow of ions and stimulation of nerve cells.

Examples of products in this group

An example of organochlorine insecticides includes:

• Ddt (dichlorodiphenyltrichloroethane): this insecticide was widely used in the past to combat malaria and other insect-borne diseases, as well as in agriculture for pest control. Its advantages include long-lasting effectiveness and high efficacy against various pests. However, its accumulation in the environment and potential impact on ecosystems led to its ban in most countries.
• Aldrin: used to combat soil pests such as mole crickets and others. Aldrin is highly toxic, especially to aquatic organisms, which limits its application.

Advantages and disadvantages

The advantages of organochlorine insecticides include their high effectiveness and long-lasting action. However, their use is limited due to resistance, toxicity to animals and humans, and long-term environmental impact.

Environmental impact

• Impact on beneficial insects (bees, predatory insects)

Organochlorine insecticides are toxic to beneficial insects such as bees, ladybugs, and other predatory insects. This can reduce the population of pollinators, disrupt the balance of ecosystems, and deteriorate crop quality.

• Residual insecticide levels in soil, water, and plants

Organochlorine insecticides have a long half-life and can persist in soil and water for extended periods, leading to their accumulation in ecosystems. This can result in water resource and soil contamination, as well as affect plants and animals consuming contaminated plants.

• Photostability and degradation of insecticides in nature

Organochlorine insecticides are photostable, meaning they break down slowly under sunlight, continuing to act and harm the ecosystem.

• Biomagnification and accumulation in food chains

The long existence of insecticides in the environment and their ability to accumulate in organisms can lead to biomagnification — the accumulation of toxic substances at each level of the food chain. This poses a threat to the health of both animals and humans.

The problem of insect resistance to insecticides

• Causes of resistance

Insects develop resistance to insecticides due to natural selection, where individuals with mutations that allow them to survive insecticide exposure pass these traits to their offspring. Over time, such insects become resistant to the chemicals, reducing the effectiveness of their use.

• Examples of resistant pests

Pests such as the colorado potato beetle, aphids, and other insects often become resistant to organochlorine insecticides after prolonged use of these products.

• Methods of preventing resistance

To prevent resistance, it is recommended to rotate insecticides with different modes of action, use safer control methods such as biological control, and combine chemical and organic methods of plant protection.

Rules for safe use of insecticides

• Preparation of solutions and dosages

It is crucial to follow the instructions for preparing insecticide solutions to avoid excessive toxicity that could harm plants and the environment. The recommended dosage should be carefully followed to prevent overdose.

• Use of protective gear when handling insecticides

When applying organochlorine insecticides, protective gear such as gloves, goggles, masks, and other personal protective equipment should be used to avoid contact with chemicals.

• Recommendations for plant treatment (time of day, weather conditions)

Application should be done in the morning or evening when the temperature is not too high, and in conditions without rain or strong wind. This helps improve the efficacy of the product and minimize its spread in the air.

• Adherence to waiting periods before harvesting

It is essential to observe the waiting periods specified on the product label to prevent chemical residues from entering the food supply.

Alternatives to chemical insecticides

• Biological insecticides

Using entomophages, such as parasitic wasps and predatory mites, provides an environmentally safe alternative to chemical insecticides. Bacterial products such as bacillus thuringiensis also effectively kill pest insects.

• Natural insecticides

The use of natural insecticides, such as neem oil, tobacco infusions, and garlic solutions, reduces the need for chemical substances without harming the ecosystem.

• Pheromone traps and other mechanical methods

Pheromone traps and mechanical devices such as sticky traps are used to control pest populations without the use of chemicals.

Examples of popular insecticides in this group

Risks and precautions

Impact on human and animal health

Organochlorine insecticides can be toxic to humans and animals, especially when misapplied. Caution should be exercised to avoid poisoning.

Symptoms of insecticide poisoning

Poisoning symptoms include headaches, nausea, vomiting, and dizziness. Immediate medical assistance is necessary in the case of poisoning.

First aid for poisoning

In case of poisoning by insecticides, rinse the mouth and eyes, take activated charcoal, and seek medical attention as soon as possible.

Conclusion

The rational use of organochlorine insecticides helps effectively combat pests, but it is important to exercise caution to avoid negative consequences for health and ecosystems. Constant monitoring of plant conditions and the use of chemical agents with consideration for safe methods of environmental and human health protection are essential.

Frequently asked questions (FAQ)

• What are organochlorine insecticides?

Organochlorine insecticides are a group of chemicals that contain chlorine atoms and are used for controlling insect pests. They affect the insect nervous system by disrupting the transmission of nerve impulses, leading to their death. The most well-known representative of this group is ddt.

• How does an organochlorine insecticide work?

Organochlorine insecticides disrupt the transmission of nerve impulses in insects by blocking the action of acetylcholinesterase, an enzyme that normally breaks down the neurotransmitter acetylcholine. This causes the accumulation of acetylcholine, leading to hyperstimulation of the nervous system and the death of the insect.

• What are the benefits of organochlorine insecticides?

Organochlorine insecticides have high toxicity to insects, provide long-term protection, and are highly effective in pest control. They can control a wide range of insects and are effective even at low doses.

• What are the main drawbacks of organochlorine insecticides?

The main drawback is their high toxicity to animals, humans, and beneficial insects such as bees. Additionally, organochlorine insecticides can accumulate in soil, water, and plants, leading to long-term environmental impacts.

• What examples of organochlorine insecticides are used in agriculture?

Examples include ddt, aldrin, and chlordane. These substances were widely used to combat pests, but their use is limited or banned in most countries due to their resistance to decomposition in nature and toxicity.

• What is the issue of insect resistance to insecticides?

Insects can develop resistance to insecticides due to prolonged or repeated use. This happens when mutations arise in the population that allow pests to survive after treatment with the chemical. This reduces the effectiveness of insecticides and requires constant switching of products.

• How can resistance in insects be prevented?

To prevent resistance, it is recommended to rotate different insecticides with various modes of action, use combination products, and apply biological pest control methods such as entomophages and other natural enemies.

• What precautions should be taken when using organochlorine insecticides?

When working with organochlorine insecticides, protective equipment such as gloves, goggles, and masks should be used to avoid contact with chemicals. It is also important to follow the instructions on the packaging regarding dosage and application times and to observe waiting periods before harvesting.

• What is the danger of organochlorine insecticides to ecosystems?

Organochlorine insecticides can destroy ecosystems by killing not only pests but also beneficial insects such as bees, as well as having toxic effects on aquatic ecosystems. These substances can accumulate in soil and biological chains, leading to long-term ecological consequences.

• Are there alternatives to organochlorine insecticides?

Yes, there are several alternative pest control methods, including biological insecticides (such as the use of entomophages), natural insecticides (such as neem oil and garlic infusions), and mechanical methods like pheromone traps. These methods are less toxic to the environment and human health but may be less effective in some situations.