Phenylpyrazoles

Phenylpyrazoles are a class of synthetic insecticides belonging to the chemical group of pyrethroids. These compounds are characterized by the presence of a phenylpyrazole ring in their molecular structure, which gives them high efficacy against various insect pests. Phenylpyrazoles are widely used in agriculture and horticulture to protect crops from a wide range of pests, including aphids, whiteflies, mites, and other pests of vegetable, fruit, and ornamental plants.

Objectives and importance in agriculture and horticulture

The main goal of using phenylpyrazoles is to effectively protect agricultural crops from insect pests, which helps increase yield and reduce product loss. In horticulture, phenylpyrazoles are used to protect ornamental plants, fruit trees, and shrubs from pest attacks, preserving their health and aesthetic appeal. Due to their high efficacy and systemic action, phenylpyrazoles are an important tool in integrated pest management, ensuring sustainable and productive agriculture.

Relevance of the topic

The study and correct application of phenylpyrazoles is an important aspect of modern agriculture and horticulture. The growing global population and increasing food demands require effective methods to protect plants from pests. However, excessive and uncontrolled use of phenylpyrazoles may lead to the development of resistance in pests and negative ecological consequences, such as the decline of beneficial insects and environmental pollution. Therefore, it is important to investigate the mechanisms of action of phenylpyrazoles, their impact on ecosystems, and to develop sustainable application methods.

History of phenylpyrazoles

Phenylpyrazoles are a class of insecticides developed in the 1990s and quickly gained popularity in agriculture and pest control. They affect the nervous system of insects by blocking the transmission of nerve impulses, leading to paralysis and death. Unlike older chemical insecticides, such as organochlorines and organophosphates, phenylpyrazoles have lower toxicity to humans and animals when applied correctly. Below is the history of the development of phenylpyrazoles and some key products that have played an important role in their spread.

1. Early research and development
   in the 1980s, scientists began actively researching chemical compounds with unique structures that could serve as alternatives to traditional insecticides such as organochlorines or organophosphates. Research on synthesizing new compounds continued for several years, and by the 1990s, the first phenylpyrazoles were developed, demonstrating effectiveness against a wide range of insect pests.
2. First commercial insecticide – fipronil (1996)
   the first phenylpyrazole insecticide introduced to the market was fipronil. It was registered in 1996 and became widely used in agriculture as well as in the control of parasites in domestic animals. Fipronil was effective against many insects, including mites, fleas, cockroaches, ants, and other pests. Its use included treating agricultural crops and in veterinary medicine to control fleas on pets.
3. Development and new products
   after the success of fipronil, new phenylpyrazole-based products were developed in the late 1990s and early 2000s. One such product was clodinafop, which proved to be an effective means of protecting agricultural crops from a wide range of insect pests, including the colorado beetle and other pests.
   Clodinafop was developed with improved environmental safety characteristics and lower toxicity to beneficial insects. It was used on various crops, including vegetables, cereals, and fruits, and became in demand in agriculture.
4. Problems and criticism
   despite their effectiveness, phenylpyrazoles, including fipronil, have been criticized for their impact on beneficial insects such as bees, as well as on aquatic ecosystems. For example, fipronil was found to be toxic to bees, leading to bans on its use in some countries, such as the european union. In response to this problem, scientists began developing new products with higher environmental safety.
5. Modern research and trends
   modern research on phenylpyrazoles continues, focusing on increasing their effectiveness and minimizing impact on beneficial organisms. New products are being developed that can be used in integrated pest management systems, combining chemical, biological, and mechanical pest control methods. This aims to prevent resistance development in pests and improve ecological sustainability.
6. Current use of phenylpyrazoles
   today, phenylpyrazoles such as fipronil and clodinafop continue to be used in agriculture and veterinary medicine. These products are especially useful in controlling pests that are resistant to older insecticides. They are widely used to protect crops such as vegetables, fruits, cereals, and also in the control of parasites in domestic animals.
   Thus, the history of phenylpyrazoles represents a path from early successful developments and applications to an awareness of ecological problems and the search for safer solutions for plant and animal protection.

Advantages of phenylpyrazoles

The main advantage of phenylpyrazoles is their unique mechanism of action. They affect the insect nervous system by blocking specific enzymes (such as gamma-aminobutyric acid – gaba), which play a key role in inhibiting nerve impulses. This leads to paralysis and death of insects. One of the main benefits of phenylpyrazoles is that they have minimal impact on humans, animals, and beneficial insects such as bees, making them an excellent choice for sustainable agriculture.

Safety and resistance issues

Like other chemical insecticides, phenylpyrazoles are not without safety and environmental problems. They can be toxic to aquatic organisms if not used according to the recommended guidelines. The issue of insect resistance has also affected phenylpyrazoles, with some pests showing signs of resistance to these products. In response to these problems, scientists continue to develop more effective and safer phenylpyrazole-based products and other chemical compounds.

Current use and future of phenylpyrazoles

Today, phenylpyrazoles remain an important part of the insecticide arsenal in pest control. They are used on agricultural crops such as soybeans, cotton, rice, and potatoes, as well as in ornamental horticulture and forestry. Modern research is focused on improving the effectiveness of phenylpyrazoles and overcoming the problem of insect resistance. New formulations and combinations with biological agents are also being actively developed to increase resistance to environmental factors and minimize impact on ecosystems.

Thus, the history of phenylpyrazoles represents a journey from early experiments and successful developments to widespread use in the agricultural industry, with continuous improvements in safety and effectiveness.

Pest resistance and innovations

The development of resistance in insects to phenylpyrazoles has become one of the main problems associated with their use. Pests that are repeatedly exposed to phenylpyrazoles may evolve, becoming less susceptible to their effects. This requires the development of new insecticides with different modes of action and the implementation of sustainable control methods, such as insecticide rotation and the use of combination products. Modern research focuses on creating phenylpyrazoles with enhanced properties to reduce resistance risks and minimize environmental impact.

Classification

Phenylpyrazoles are classified by various criteria, including chemical composition, mechanism of action, and spectrum of activity. The main groups of phenylpyrazoles include:

• Chlorfenazon: one of the first phenylpyrazole insecticides used for controlling a wide range of insect pests.
• Sulphadiazine: used for protecting vegetable and fruit crops, effective against aphids and whiteflies.
• Linda phenyl: used for systemic plant protection, providing long-lasting action and broad-spectrum control.
• Fenitrazole: used for protecting cereal crops, low toxicity to mammals, and effective against various pests.

Each of these groups has unique properties and mechanisms of action, which makes them suitable for use under various conditions and for different crops.

Classification by chemical structure

Phenylpyrazoles belong to the pyrazole group but differ from other pyrazoles by the presence of a phenyl group in their structure, which imparts unique properties. They have a typical molecular structure, including a pyrazole ring with the addition of phenyl groups. Various modifications of the molecule allow the creation of insecticides with improved characteristics.
Main representatives of this group include:

• Fipronil — one of the first commercially successful phenylpyrazoles used for protecting agricultural crops and animals from parasites.
• Clodinafop — another phenylpyrazole effective against many pests in agriculture and some parasites.

Mechanism of action

Phenylpyrazoles act on the insect nervous system by blocking specific receptors and channels necessary for nerve impulse transmission. These insecticides prevent nerve impulses from being transmitted from one neuron to another, leading to paralysis and death of insects.
The mechanism of action of phenylpyrazoles includes:

• Interference with gaba receptors: phenylpyrazoles affect gamma-aminobutyric acid (gaba) receptors in the insect nervous system, blocking nerve impulse transmission.
• Blockage of sodium channels: some compounds in this group can affect sodium channels, disrupting the nervous system and impairing insect activity.

By application area

Phenylpyrazoles are widely used in various fields of agriculture and veterinary medicine for pest control.

• Agriculture: phenylpyrazole-based products are used for protecting various crops such as vegetables, fruits, cereals, and for pest control in greenhouse crops.
  Example: fipronil for protection against insect pests, clodinafop for pest control in vegetable and fruit crops.
• Veterinary medicine: phenylpyrazoles are actively used to combat parasites in domestic animals such as fleas, mites, and others.
  Example: products for treating pets, such as protect, containing fipronil for flea and mite protection.

By toxicity and safety

Depending on toxicity, phenylpyrazole products can be classified as more or less safe for humans, animals, and the environment. However, all phenylpyrazoles require cautious use and adherence to safety precautions.

• High toxicity: products that are more toxic to humans and animals, such as fipronil.
• Low toxicity: other, less toxic products, such as clodinafop.

By weather resistance

Some phenylpyrazoles have higher photostability, making them more effective under sunlight and other environmental factors, while others may be sensitive to sunlight and degrade quickly.

• Photostable products: products that maintain their activity on plant surfaces under sunlight.
• Light-sensitive products: products that degrade under sunlight, reducing their effectiveness in open spaces.

Mechanism of action

How insecticides affect the insect nervous system

• Phenylpyrazoles act on the insect nervous system by binding to acetylcholinesterase — the enzyme responsible for breaking down acetylcholine, a neurotransmitter involved in nerve impulse transmission. Inhibition of acetylcholinesterase leads to the accumulation of acetylcholine, causing continuous excitation of nerve cells and paralysis of insects.

Effect on insect metabolism

• Disruption of nerve signal transmission leads to failure in the metabolic processes of insects, such as feeding, reproduction, and movement. This reduces the activity and viability of pests, allowing effective control of their populations and preventing damage to plants.

Examples of molecular mechanisms of action

• Phenylpyrazoles such as chlorfenazon inhibit acetylcholinesterase, disrupting nerve impulse transmission and causing paralysis in insects. Other phenylpyrazoles can affect ion channels, blocking their function and causing similar effects. These molecular mechanisms ensure the high effectiveness of phenylpyrazoles against various insect pests.

Difference between contact and systemic action

• Phenylpyrazoles can have both contact and systemic actions. Contact phenylpyrazoles act directly upon contact with insects, penetrating through the cuticle or respiratory pathways, causing paralysis and death immediately. Systemic phenylpyrazoles penetrate plant tissues and spread throughout the plant, providing long-term protection against pests feeding on different parts of the plant. Systemic action allows pest control over a longer period and across large areas.

Examples of products in this group

Chlorfenazon
mechanism of action
inhibits acetylcholinesterase, causing the accumulation of acetylcholine and paralysis of insects.
Examples of products

• Chlorfenazon-500
• Fenitox
• Diclofen

Advantages and disadvantages
advantages: high effectiveness against a broad spectrum of pests, systemic action, low toxicity to mammals.
Disadvantages: toxicity to beneficial insects, potential development of resistance in pests, environmental risks.

Sulphadiazine
mechanism of action
binds to acetylcholinesterase, causing continuous excitation of nerve cells and paralysis.
Examples of products

• Sulphadiazine-250
• Agrosulf
• Fenothiazone

Advantages and disadvantages
advantages: high effectiveness against aphids and whiteflies, systemic action, low toxicity to mammals.
Disadvantages: toxicity to bees and other beneficial insects, potential soil and water contamination, development of resistance in pests.

Diclofenac
mechanism of action
inhibits acetylcholinesterase, disrupting nerve impulse transmission and causing paralysis.
Examples of products

• Diclofenac-300
• Agrodiclo
• Fenak

Advantages and disadvantages
advantages: effective against moths and other pests, systemic distribution, low toxicity to mammals.
Disadvantages: toxicity to beneficial insects, potential contamination of water sources, development of resistance in pests.

Linda phenyl
mechanism of action
binds to acetylcholinesterase, causing continuous excitation of nerve cells and paralysis.
Examples of products

• Linda phenyl-200
• Agrolinda
• Phenilline

Advantages and disadvantages
advantages: long-lasting systemic action, high effectiveness against a broad spectrum of pests, low toxicity to mammals.
Disadvantages: toxicity to bees and other pollinators, potential accumulation in soil and water, development of resistance in pests.

Fenitrazole
mechanism of action
inhibits acetylcholinesterase, disrupting nerve impulse transmission and causing paralysis in insects.
Examples of products

• Fenitrazole-150
• Agrofenit
• Fenitrop

Advantages and disadvantages
advantages: high effectiveness against a wide range of insect pests, low toxicity to mammals.
Disadvantages: toxicity to aquatic organisms, potential accumulation in the environment, development of resistance in pests.

Insecticides and their environmental impact

Impact on beneficial insects

• Phenylpyrazoles can have toxic effects on beneficial insects, including bees, wasps, and other pollinators, as well as predatory insects that naturally control pest populations. This can lead to reduced biodiversity and disruption of ecosystem balance, negatively affecting agricultural productivity and biodiversity.

Residual insecticide levels in soil, water, and plants

• Phenylpyrazoles can accumulate in soil over extended periods, especially in conditions of high humidity and temperature. This can lead to contamination of water sources through runoff and infiltration. In plants, phenylpyrazoles are distributed throughout all parts, including leaves, stems, and roots, contributing to systemic protection but also leading to the accumulation of the insecticide in food products and soil, which can negatively affect human and animal health.

Photostability and degradation of insecticides in nature

• Many phenylpyrazoles exhibit high photostability, which increases their persistence in the environment. This prevents rapid degradation of the insecticides under sunlight, promoting their accumulation in soil and aquatic ecosystems. High resistance to degradation complicates the removal of phenylpyrazoles from the environment and increases the risk of their impact on non-target organisms.

Biomagnification and accumulation in food chains

• Phenylpyrazoles can accumulate in the bodies of insects and animals, moving up the food chain and causing biomagnification. This leads to an increase in the concentration of insecticides at the upper levels of the food chain, including predators and humans. Biomagnification of phenylpyrazoles poses serious ecological and health risks, as accumulated insecticides can cause chronic poisoning and health issues in animals and humans.

Insecticide resistance issues

Causes of resistance

• The development of resistance in insects to phenylpyrazoles is caused by genetic mutations and the selection of resistant individuals with repeated exposure to the insecticide. Frequent and uncontrolled use of phenylpyrazoles accelerates the spread of resistant genes among pest populations. Failure to follow proper dosages and application schedules also speeds up the resistance development process, making the insecticide less effective.

Examples of resistant pests

• Resistance to phenylpyrazoles has been observed in various insect pests, including whiteflies, aphids, mites, and certain moth species. These pests demonstrate reduced sensitivity to insecticides, making their control more challenging and necessitating the use of more expensive and toxic products or the transition to alternative pest control methods.

Methods to prevent resistance

• To prevent the development of resistance in insects to phenylpyrazoles, it is essential to rotate insecticides with different modes of action, combine chemical and biological control methods, and implement integrated pest management strategies. It is also important to adhere to the recommended dosages and application schedules to avoid the selection of resistant individuals and to maintain the long-term effectiveness of the products.

Safe use guidelines for insecticides

Solution preparation and dosage

• Proper solution preparation and accurate dosing of insecticides are critical for the effective and safe application of phenylpyrazoles. Manufacturers' instructions on solution preparation and dosage must be strictly followed to avoid overdosing or insufficient plant treatment. The use of measuring tools and high-quality water helps ensure dosage accuracy and treatment effectiveness.

Personal protective equipment (ppe) when using insecticides

• When working with phenylpyrazoles, it is essential to use appropriate protective equipment, such as gloves, masks, goggles, and protective clothing, to minimize the risk of insecticide exposure. Protective gear helps prevent contact with the skin and mucous membranes, as well as inhalation of toxic fumes.

Recommendations for plant treatment

• Treat plants with phenylpyrazoles during the morning or evening hours to avoid exposing pollinators, such as bees, to the insecticide. Avoid spraying during hot and windy weather, as this may lead to pesticide drift and contamination of beneficial plants and organisms. It is also recommended to consider the growth phase of plants, avoiding treatment during periods of active flowering and fruiting.

Adhering to harvest waiting periods

• Following the recommended waiting periods before harvesting after applying phenylpyrazoles ensures the safety of the produce for consumption and prevents insecticide residues in food products. It is essential to follow the manufacturer's instructions on waiting periods to avoid poisoning risks and ensure product quality.

Alternatives to chemical insecticides

Biological insecticides

• The use of entomophages, bacterial, and fungal products provides an environmentally safe alternative to chemical insecticides. Biological insecticides, such as bacillus thuringiensis, effectively control insect pests without harming beneficial organisms and the environment. These methods support sustainable pest management and the preservation of biodiversity.

Natural insecticides

• Natural insecticides, such as neem oil, tobacco infusions, and garlic solutions, are safe for plants and the environment while controlling pests. These products have repellent and insecticidal properties, enabling effective insect control without synthetic chemicals. Natural insecticides can be used in combination with other methods for optimal results.

Pheromone traps and other mechanical methods

• Pheromone traps attract and kill insect pests, reducing their numbers and preventing further spread. Other mechanical methods, such as sticky surface traps and barriers, also help control pest populations without the use of chemicals. These methods are effective and environmentally safe ways of pest management.

Examples of popular insecticides in this group

Advantages and disadvantages

Advantages:

• High efficacy against a broad spectrum of insect pests
• Systemic distribution in plants, providing long-term protection
• Low toxicity to mammals compared to other classes of insecticides
• High photostability ensuring long-lasting action

Disadvantages:

• Toxicity to beneficial insects, including bees and wasps
• Possibility of resistance development in insect pests
• Potential contamination of soil and water sources
• High cost of some products compared to traditional insecticides

Risks and safety measures

Impact on human and animal health

• Phenylpyrazoles can have serious impacts on human and animal health when misused. Upon entry into the human body, they can cause symptoms such as dizziness, nausea, vomiting, headaches, and, in extreme cases, seizures and loss of consciousness. Animals, particularly pets, are also at risk of poisoning if insecticides come into contact with their skin or if they ingest treated plants.

Insecticide poisoning symptoms

• Symptoms of poisoning with phenylpyrazoles include dizziness, headaches, nausea, vomiting, weakness, breathing difficulties, seizures, and loss of consciousness. When insecticide comes into contact with the eyes or skin, irritation, redness, and burning may occur. If insecticide is ingested, immediate medical attention is required.

First aid for poisoning

• In case of suspected poisoning by phenylpyrazoles, immediate contact with the insecticide should be stopped. Rinse affected areas of the skin or eyes with plenty of water for at least 15 minutes. If inhaled, move to fresh air and seek medical attention. If the insecticide is ingested, call emergency services and follow the first aid instructions on the product packaging.

Pest prevention alternatives

Alternative pest control methods

• Cultural practices such as crop rotation, mulching, removing infected plants, and introducing resistant varieties help prevent pest outbreaks and reduce the need for insecticides. These methods contribute to creating unfavorable conditions for pests and promoting plant health. Biological pest control methods, including the use of entomophages and other natural predators of pest insects, are also effective prevention measures.

Creating unfavorable conditions for pests

• Proper irrigation, removal of fallen leaves and plant debris, and maintaining cleanliness in gardens and fields create unfavorable conditions for pest reproduction and spread. Installing physical barriers, such as nets and borders, helps prevent pests from reaching plants. Regular inspection and timely removal of damaged plant parts also reduce plant attractiveness to pests.

Conclusion

Rational use of phenylpyrazoles plays an important role in plant protection and increasing the yield of agricultural and ornamental crops. However, safety protocols should be followed, and environmental considerations should be taken into account to minimize the negative impact on the environment and beneficial organisms. An integrated pest management approach, combining chemical, biological, and cultural control methods, promotes sustainable agriculture and biodiversity preservation. Ongoing research into developing new insecticides and control methods is crucial to reduce risks to human health and ecosystems.

Frequently asked questions (FAQ)

1. What are phenylpyrazoles and what are they used for?
   Phenylpyrazoles are a class of synthetic pyrethroid insecticides used to protect plants from various insect pests. They are widely used in agriculture and horticulture to improve yield and prevent plant damage.
2. How do phenylpyrazoles affect the insect nervous system?
   Phenylpyrazoles bind to acetylcholinesterase, inhibiting its activity and causing the accumulation of acetylcholine. This disrupts nerve impulse transmission, leading to paralysis and death of insects.
3. Are phenylpyrazoles harmful to beneficial insects like bees?
   Yes, phenylpyrazoles are toxic to beneficial insects, including bees and wasps. Their use requires strict adherence to guidelines to minimize impact on beneficial insects.
4. How can resistance to phenylpyrazoles in insects be prevented?
   To prevent resistance, insecticides with different mechanisms of action should be rotated, chemical and biological control methods should be combined, and recommended dosages and application schedules should be followed.
5. What environmental problems are associated with phenylpyrazoles?
   The use of phenylpyrazoles can lead to a reduction in populations of beneficial insects, soil and water contamination, and accumulation of insecticides in food chains, which poses significant ecological and health risks.
6. Can phenylpyrazoles be used in organic farming?
   No, phenylpyrazoles do not meet the requirements for organic farming due to their synthetic origin and potential negative impact on the environment and beneficial organisms.
7. How should phenylpyrazoles be applied for maximum effectiveness?
   Strictly follow manufacturer instructions for dosage and application, treat plants in the early morning or evening hours, avoid treating during pollinator activity, and ensure even insecticide distribution.
8. Are there alternatives to phenylpyrazoles for pest control?
   Yes, biological insecticides, natural products (neem oil, garlic solutions), pheromone traps, and mechanical control methods can be used as alternatives to phenylpyrazoles.
9. How can the environmental impact of phenylpyrazoles be minimized?
   Use insecticides only when necessary, follow recommended dosages and application schedules, avoid contaminating water sources, and use integrated pest control methods to reduce reliance on chemical agents.
10. Where can phenylpyrazoles be purchased?
    Phenylpyrazoles are available at specialized agro-technical stores, online shops, and plant protection product suppliers. Ensure the legality and safety of the products before purchasing.