Fumigants

Fumigants are chemical substances designed to destroy pests, pathogenic microorganisms, and weed seeds in the soil, as well as to sterilize spaces from insects and other small organisms. They are used in both agriculture and horticulture to protect crops from various threats. Fumigants can be in gaseous or liquid form, applied in enclosed spaces such as greenhouses, soils, grain storage, and other agricultural facilities.

Goals and importance of use in agriculture and horticulture

The main goal of using fumigants is to ensure effective protection of plants from a wide range of pests, including insects, fungal, and bacterial diseases. In agriculture, fumigants are used for soil treatment before planting crops, destroying harmful organisms, and increasing crop yields. In horticulture, they help control pests on ornamental and fruit plants, preserving their health and aesthetic value. Fumigants are also used to sterilize grain, seeds, and other agricultural products, preventing the spread of diseases and pests.

Relevance of the topic

With the growing global population and increasing demand for food, effective and sustainable pest management has become critically important. Studying and properly applying fumigants helps minimize pest damage, increase agricultural productivity, and reduce economic losses. It is also important to consider the environmental aspects of using fumigants to prevent negative impacts on the environment and beneficial organisms. Modern pest control methods aim to reduce the use of chemicals and transition to more environmentally friendly and safer plant protection methods.

History

Fumigants play an important role in the prevention and treatment of plant diseases, as well as in the sanitary treatment of goods. Their history spans several decades, and as technology has advanced, various fumigants have been developed that differ in composition and mechanism of action.

Early research and first fumigants

The use of fumigants dates back to the 19th century when the first chemicals were introduced that could be applied in gaseous form to eliminate pests. During this period, chemical research on fumigants was not as advanced as it is now, and applications were limited to experiments with natural compounds.

• sulfur: one of the first fumigants used to control fungi, pests on plants, and for disinfecting warehouses. Sulfur was used as early as ancient egypt to preserve food from insects and fight plant diseases.

Development of fumigation in the 20th century

In the early 20th century, the use of fumigants became more scientifically grounded as chemists began developing new substances that were more effective and safer for humans and animals.

• hydrogen cyanide (HCN): in the early 20th century, hydrogen cyanide was widely used as a fumigant, especially for disinfecting rooms from insect pests. However, as toxicological studies advanced, its use was restricted due to its high toxicity to humans and animals.
• methyl bromide (CH3Br): this substance became popular in the 1940s as an effective fumigant used for protecting agricultural crops and food storage. However, as environmental standards developed and the impact on the ozone layer was recognized, its use began to decrease.

Environmental issues and bans

In the 1970s and 1980s, it became clear that some fumigants, such as methyl bromide, could significantly disrupt ecosystems. It was decided to impose restrictions on the use of methyl bromide, and in 1992, the montreal protocol was signed, under which countries committed to gradually phasing out its use. This led to the development of alternative fumigants that did not have such destructive effects on the environment.

• phosgene: developed in the 1970s as an alternative fumigant to combat pests. It was used in agriculture and warehouses, but like other chemicals, it was restricted due to its toxicity and environmental impact.

Modern fumigants and their application

Today, many alternative fumigants meet stricter environmental and safety standards. Modern fumigants are used in agriculture for protecting food supplies, as well as in medical applications for disinfecting and sterilizing rooms.

• sulfur (reuse): sulfur continues to be used as a fumigant, especially to fight fungal plant diseases. With the development of technology, new methods for applying sulfur have been developed, such as sublimation of sulfur, making its use more effective and safer.
• sulfur fluoride (SF2): with the development of new technologies, sulfur fluoride has become used as an alternative to methyl bromide in pest control. This substance is safer for the ozone layer and is used in various fields such as agriculture, food storage, and room disinfection.
• ethylene oxide (C2H4O): this gaseous substance is used for sterilization and disinfection in various fields, including medicine and food storage. Ethylene oxide is an effective fumigant and is used both in its pure form and in mixtures with other gases.

The future of fumigation

With the advancement of science and technology, new substances are being developed that can be used as fumigants with less environmental impact. It is expected that in the future, fumigants will be safer for human health and the environment and will be more effective in combating pests and diseases.

Example:

• aluminum phosphide: used as a fumigant in warehouses and to protect food from pests. This fumigant is safe for use in closed rooms and is effective against a wide range of insects.

The history of fumigants spans over a century of research and the use of chemicals to eliminate pests. The importance of fumigation in agriculture and other industries is clear; however, with scientific progress, it is necessary to consider the ecological and toxicological consequences, leading to the search for safe and effective alternatives to traditional fumigants.

Classification

Fumigants are classified according to various criteria, including chemical composition, mechanism of action, and field of application. The main groups of fumigants include:

• Organic fumigants: synthetic organic compounds, such as metamfose and dimethyl phosphite.
• Inorganic fumigants: such as hydrogen sulfide and phosphine.
• Biological fumigants: using biological agents to kill pests, e.g., bacillus thuringiensis bacteria.
• Gaseous fumigants: used for soil and room sterilization, e.g., methylene chloride and ethylene oxide.
• Liquid fumigants: used in solution form for plant and soil treatment.

Depending on the mechanism of action, composition, and area of application, fumigants can be classified into several groups. Let's review the main categories of fumigants:

Natural fumigants

These are substances used in gaseous form and have natural origins. They are generally considered to be less toxic to the environment and humans compared to synthetic fumigants.

• sulfur: used for disinfection and pest control, especially in greenhouses and horticulture. Sulfur can be in gaseous or vapor form and is used to combat fungi and insect pests.
• essential oils: some essential oils (e.g., eucalyptus oil, mint, or citrus) are used to protect plants from insects. These oils have repellent properties and can inhibit the development of some microorganisms.

Synthetic fumigants

This group includes chemicals that have been synthesized for more targeted pest control. They are highly toxic but may have side effects such as environmental pollution and increased resistance of pests.

• methyl bromide (ch3br): one of the most widely known fumigants. It is used to protect agricultural crops, disinfect rooms, and goods. However, since the late 1990s, its use has been restricted due to the threat of ozone layer depletion.
• hydrogen cyanide (hcn): used for disinfection and pest control, primarily for treating warehouses and rooms. Hydrogen cyanide is highly toxic and requires caution during use.
• metal phosphides: these include aluminum phosphide and magnesium phosphide. These substances are used to protect grains and other products. They release phosphine, a toxic gas, when they come into contact with moisture.

Biological fumigants

These are substances derived from biological sources or synthesized using living organisms. Biological fumigants are designed to combat pests with minimal impact on ecology and humans.

• ethylene oxide (C2H4O): a gas used for sterilization and disinfection in various fields, such as medicine, the food industry, and agriculture. It has fumigant properties and is effective against a wide range of microorganisms.
• bacterial and fungal fumigants: used to combat fungal diseases and some insects. For example, extracts or preparations based on bacillus bacteria, which can eliminate pests in gaseous form.

Fumigants with growth-regulating effects

These fumigants are used to suppress the growth and development of pests at different stages of their life cycle, as well as for disinfection.

• aluminum phosphide: one of the most common fumigants for grain storage and other agricultural products. This chemical substance releases phosphine, which destroys pests by disrupting their breathing and metabolism.
• phosphine: used for disinfection and pest control in closed spaces. Phosphine is actively used to combat pests in storage facilities, warehouses, and industrial sites.

Naturally-synthetic fumigants

This category includes substances that can be both synthetic and natural. They have repellent or toxic effects on pests and are used in various fields, such as agriculture, food storage, and even household settings.

• carbophos: a synthetic fumigant that is actively used for plant protection in horticulture, as well as for disinfecting rooms and vehicles.
• dimethoate: used as a fumigant for pest control, including for the protection of vegetables, fruits, and flowers. It has a wide range of action and is used for the prevention of plant diseases.

Mechanism of action

• How insecticides affect the insect nervous system

Fumigants act on the insect nervous system by blocking nerve impulse transmission. They may inhibit enzymes, such as acetylcholinesterase, disrupting nerve signal transmission and causing paralysis of the insects. Some fumigants block sodium channels in nerve cells, causing continuous excitation and death of pests.

• Impact on insect metabolism

Fumigants can affect the metabolic processes of insects by disrupting the synthesis of proteins, carbohydrates, and lipids. This leads to decreased viability and reproductive ability of the insects. Disruption of normal metabolism hinders growth and development, reducing insect populations.

• Examples of molecular mechanisms of action

Fumigants like chlorpyrifos inhibit acetylcholinesterase, leading to acetylcholine accumulation and disrupted nerve transmission. Other fumigants may act on sodium channels, causing continuous depolarization of nerve cells and paralysis. For example, organophosphate fumigants block enzymes essential for the normal functioning of the nervous system, leading to insect death.

• Difference between contact and systemic effects

Contact fumigants act directly when in contact with the pests, killing them immediately. They penetrate the cuticle or respiratory tracts of insects, affecting their nervous system. Systemic fumigants penetrate plant tissues, spreading throughout the plant and providing protection from pests that feed on plant tissues. Systemic fumigants offer long-term pest control but require more careful dosage and application timing.

Main groups of insecticides by chemical composition

Organophosphates

Mechanism of action

Organophosphates inhibit acetylcholinesterase, disrupting nerve transmission and causing insect paralysis.

Examples of products

• Metamfose
• Phosfention
• Ethylphosphorone

Advantages and disadvantages

Advantages: high efficiency, broad spectrum of action, fast effect.

Disadvantages: high toxicity to humans and animals, environmental hazards, potential resistance development in pests.

Pyrethroids

Mechanism of action

Pyrethroids block sodium channels in the insect nervous system, causing paralysis and death.

Examples of products

• Permethrin
• Deltamethrin
• Lambda-cyhalothrin

Advantages and disadvantages

Advantages: low toxicity to mammals, high efficiency, light resistance.

Disadvantages: toxicity to beneficial insects (bees, wasps), resistance development in pests, possible accumulation in the environment.

Neonicotinoids

Mechanism of action

Neonicotinoids act on nicotinic acetylcholine receptors, causing continuous excitation of nerve cells.

Examples of products

• Imidacloprid
• Thiamethoxam
• Clothianidin

Advantages and disadvantages

Advantages: systemic action, high efficiency against aphids and whiteflies, decomposition resistance.

Disadvantages: toxicity to bees and other pollinators, potential accumulation in aquatic ecosystems, resistance development in pests.

Carbamates

Mechanism of action

Carbamates inhibit acetylcholinesterase, similar to organophosphates, disrupting the insect nervous system.

Examples of products

• Carbaryl
• Methomyl
• Carbendazim

Advantages and disadvantages

Advantages: high efficiency, broad spectrum of action.

Disadvantages: toxicity to humans and animals, impact on beneficial insects, environmental risks.

Phenylpyrazoles

Mechanism of action

Phenylpyrazoles affect the central nervous system of insects, disrupting nerve signal transmission and causing paralysis.

Examples of products

• Chlorfenapyr
• Sulfadiazine

Advantages and disadvantages

Advantages: high efficiency against a wide range of insect pests, low toxicity to mammals.

Disadvantages: toxicity to aquatic organisms, potential accumulation in the environment.

Insecticides and their impact on the environment

• Impact on beneficial insects

Fumigants, especially contact insecticides, harm beneficial insects such as bees, wasps, and predatory insects, disrupting ecosystem balance and reducing biological control effectiveness. The destruction of beneficial insects leads to decreased pollination and weakened natural pest control mechanisms.

• Residual insecticide levels in soil, water, and plants

Fumigants can remain in the soil, water, and plants for a long time, causing environmental contamination and accumulation of toxic substances in food chains. Residual insecticides can have long-term impacts on the environment, reducing biodiversity and disrupting natural processes.

• Photostability and decomposition of insecticides in nature

Many insecticides are highly photostable, which increases their persistence, but makes them difficult to break down in nature. This leads to their accumulation in the environment and potential biomagnification. For example, neonicotinoids break down slowly under sunlight, contributing to their long-term presence in the ecosystem.

• Biomagnification and accumulation in food chains

Insecticides can accumulate in insect and animal tissues, leading to biomagnification and increased toxicity at higher levels of the food chain, including humans. This causes serious ecological and health problems, as accumulated insecticides can cause poisoning and health issues in animals and humans.

The problem of pest resistance to insecticides

• Causes of resistance development

Frequent and uncontrolled use of insecticides contributes to the selection of resistant pest populations. Genetic mutations and gene flow between insects accelerate the development of resistance. Noncompliance with recommended dosages and application regimes also promotes resistance development.

• Examples of resistant pests

Resistance has developed in pests such as whiteflies, aphids, mites, and some species of moths. These pests show reduced sensitivity to insecticides, making them difficult to control and requiring the use of stronger and more toxic products.

• Methods to prevent resistance

To prevent resistance, it is necessary to rotate insecticides with different mechanisms of action, combine chemical and biological control methods, and apply integrated pest management strategies. It is also essential to adhere to recommended dosages and application regimes to avoid selecting resistant individuals.

Safe use of insecticides

• Preparation of solutions and dosages

It is essential to strictly follow the manufacturer's instructions for preparing solutions and dosing insecticides. Overuse can lead to environmental problems and resistance development in pests. Using measuring tools for precise dosing helps avoid mistakes and ensures effective and safe insecticide use.

• Use of protective equipment

When working with insecticides, protective equipment such as gloves, masks, goggles, and protective clothing should be worn to minimize human exposure. Protective gear helps prevent contact with skin and mucous membranes, as well as inhalation of toxic insecticide vapors.

• Recommendations for plant treatment

Treat plants in the early morning or evening to avoid insecticide exposure to bees and other pollinators. Avoid treatment in windy weather and rainy days, as this can lead to the spread of insecticides to beneficial plants and organisms.

• Waiting periods before harvesting

It is necessary to observe the recommended waiting periods before harvesting after applying insecticides to avoid chemical residues in food products. Observing waiting periods ensures the safety of consumption and prevents risks to human health.

Alternatives to chemical insecticides

• Biological insecticides

Using entomophages, bacterial, and fungal preparations to control insect pests is an environmentally safe

Alternative to chemical insecticides. Biological insecticides such as bacillus thuringiensis effectively combat pests without harming beneficial organisms and the environment.

• Natural insecticides

Using natural agents like neem oil, tobacco infusions, and garlic solutions effectively controls pests without using synthetic chemicals. These methods repel insects and prevent their reproduction, preserving plant and ecosystem health.

• Pheromone traps and other mechanical methods

Pheromone traps attract and destroy insect pests, reducing their populations and preventing their spread. Other mechanical methods, such as sticky traps and barriers, also help control pest populations without using chemicals.

Examples of popular insecticides from this group

Product name	Active ingredient	Mechanism of action	Application area
Metamethion	Phosphine	Blockage of respiratory systems	Grain storage, soil
Organophosphate fumigants	Chlorpyrifos	Inhibition of acetylcholinesterase	Agricultural crops
Simenda	Simenda	Cell dehydration	Vegetable crops
Sulfur	Sulfur	Oxidative effect	Fruit trees, vegetable crops
Methionyl	Methionyl	Inhibition of metabolic processes	Garden plants, soil

Advantages and disadvantages

Advantages

• High effectiveness against a wide range of pests
• Quick action ensuring immediate population reduction
• Usable in various conditions and on different crops

Disadvantages

• High toxicity to humans and animals if misused
• Environmental hazards, including soil and water contamination
• Possibility of pest resistance development, reducing effectiveness

Risks and precautions

• Impact on human and animal health

Improper or excessive use of insecticides can cause poisoning in humans and animals. Symptoms can range from mild skin and eye irritation to serious neurological and respiratory disorders. The toxicity of insecticides requires strict adherence to safety regulations during use.

• Symptoms of insecticide poisoning

Symptoms of poisoning may include dizziness, nausea, vomiting, weakness, convulsions, difficulty breathing, and loss of consciousness. If insecticide contacts the eyes or skin, rinse the affected area immediately with plenty of water.

• First aid for poisoning

In case of insecticide contact with the skin or eyes, rinse the affected area with water for at least 15 minutes. If inhaled, move to fresh air and seek medical help. If ingested, call emergency services and follow first aid instructions.

Pest prevention

• Alternative pest control methods

Using cultural practices such as crop rotation, mulching, and proper plant care helps prevent pest outbreaks and reduces the need for insecticides. These methods create unfavorable conditions for pests and improve plant health.

• Creating unfavorable conditions for pests

Proper irrigation, removing fallen leaves and plant debris, and maintaining garden cleanliness create unfavorable conditions for pest breeding and reduce their populations. Using physical barriers such as nets and borders also helps prevent pests from accessing plants.

Conclusion

Rational use of insecticides plays an important role in plant protection and increasing yields. Following safety guidelines and proper dosage helps minimize environmental impact and health risks. It is also important to integrate chemical methods with biological and cultural pest control methods to achieve sustainable pest management and maintain ecosystem balance.

Frequently asked questions (FAQ)

What are fumigants?

Fumigants are chemical substances used to destroy pests, pathogenic microorganisms, and weed seeds in the soil and on plants. They can be applied as gases or liquids and are designed to sterilize soil, grain, and agricultural structures.

What types of fumigants exist?

The main types of fumigants include organic fumigants (e.g., metamfose), inorganic fumigants (e.g., hydrogen sulfide), biological fumigants (e.g., bacillus thuringiensis bacteria), and gaseous fumigants (e.g., methylene chloride).

How do fumigants affect insects?

Fumigants act on the insect nervous system, blocking nerve impulse transmission and causing paralysis and death of pests. They may inhibit enzymes or block nerve channels, disrupting the normal life processes of insects.

Can fumigants be used in greenhouses?

Yes, fumigants are widely used in greenhouses for soil sterilization and pest control. However, safety rules must be followed, and appropriate protective equipment should be used, along with dosage and application time recommendations.

Are fumigants harmful to beneficial insects?

Yes, fumigants can be toxic to beneficial insects, including bees and predatory insects. Therefore, it is important to apply fumigants with caution, avoiding application during pollinator activity periods and carefully monitoring the use of these products.

How to prevent pest resistance to fumigants?

To prevent resistance, it is necessary to rotate fumigants with different mechanisms of action, combine chemical and biological control methods, and follow recommended dosage and application schedules.

Can fumigants pollute the environment?

Yes, fumigants can accumulate in soil, water, and plants, leading to ecosystem contamination and accumulation of toxic substances in food chains. This causes serious environmental and health problems.

What alternatives to fumigants exist?

Alternatives include biological insecticides, natural remedies (neem oil, garlic solutions), pheromone traps, and mechanical control methods. These approaches allow effective pest control without harming the environment and beneficial organisms.

How to choose the appropriate fumigant for a specific crop?

The choice of fumigant depends on the type of pest, the plant's age, environmental conditions, and adherence to safety regulations. It is recommended to consult with agronomists and follow manufacturers' guidelines for effective and safe product application.

Where can fumigants be purchased?

Fumigants are available in specialized agricultural stores, online shops, and from plant protection suppliers. Before purchasing, ensure the legality and safety of the products being used.