eChapters

The chemicals, which can destroy pests or prevent their occurrence by their chemical action are known as ‘Pesticides’. Pesticides include ‘insecticides’, acaricides’, ‘nematicides’, rodenticides’, molluscicides’ etc., which are used to destroy insect pests, mites, nematodes, rodents, slugs and snails respectively. Pesticides have been used even before the time when man never knew how to read and write. Even before 200 BC, several substances were known to control pests. Sulfur, arsenic poisons, fluorine poisons, as well as some plant extracts and oils were used to control pests. However, these substances could destroy only a few specific pests only to some extent.

Advances in the invention of pesticides

The invention of many of the present day pesticides started only after 1867. ‘Paris green’, a synthetic chemical was the first pesticide used to control the ‘Colorodo beetles’ of potato. Up to 1939, only a few inorganic chemical compounds and plant poisons were used as pesticides. Only after the Second World War much advances were made in chemical research. After the invention of DDT in 1939, a revolution had started in the field of pest control. Following the introduction of DDT, several other pesticides were identified and introduced for pest control. In 1941, BHC was invented by the British and French scientists. During the same period, organophosphorus pesticides were invented by the German scientists and parathion, malathion, demeton etc. were introduced.

For effective and economic control of pests, besides selection of appropriate plant protection chemicals, application of the chemicals at the most vulnerable growth stage of the pests and use of chemicals at the correct dosage, selection of proper plant protection appliances to carry out the operation is also of vital importance, so as to ensure uniform application of the chemicals.

Plant protection chemicals are mostly used as sprays and dusts using sprayers and dusters respectively. However, in most of the cases spraying is preferred to dusting. Different types of sprayers and dusters are being used for these operations and in both, there are manually operated as well as power operated equipments and in sprayers there are both hydraulic and pneumatic types of sprayers.

The nature of the pesticide formulations to be used and the purpose for which they are used also determine the type of equipment to be used. Dusters are used for dusting insecticidal dust formulations. Sprayers are used for spraying insecticidal liquid formulations. Granular applicators are used to apply granular formulations. Fumigators are used to apply fumigants to fumigate godowns, warehouses, rat holes etc. Soil injectors are used to inject pesticides at a particular depth of soil under pressure. Flame throwers are used to throw f lames at specified targets.

Introduction

Insects, classified under the Class Insecta within the Phylum Arthropoda, exhibit diverse characteristics. Sometimes, distinguishing between different arthropods is necessary to confirm their classification as insects. Biologists frequently employ dichotomous keys, systematic tools designed to assist in organism identification, to navigate this task.

Instructions

Follow the steps outlined below to identify the insects described. Utilize the provided dichotomous keys and accompanying figures to aid in the identification process.

Objective

The aim of this practical is to categorize insects based on their wing characteristics.

Introduction: Insect classification, as outlined by A.D. Imms (1957), divides Class Insecta or Hexapoda into two primary groups:

Group 1: Apterygota: These insects lack wings, and the absence of wings is considered primitive. Metamorphosis is minimal or absent. Adults typically possess one or more pairs of pregenital abdominal appendages. The mandible of adults usually articulates with the head capsule at a single point. This group comprises four orders:

1. Thysanura - Example: Silverfish

2. Diplura - Example: Japygids

3. Protura - Example: Telson tails or proturans

4. Collembola - Example: Springtails

Objective: The objective of this practical exercise is to understand the taxonomic features of the order Orthoptera and classify its suborders and families.

Observations: Order - Orthoptera (Orthos = straight, pteron = wing) Includes grasshoppers, crickets, and locusts.

Key Characteristics

1. Presence of wings, either fully developed, shortened (brachypterous), or absent (apterous).

2. Mouthparts are of the biting and chewing type (mandibulate).

3. Hind legs are typically enlarged and adapted for jumping.

4. Two pairs of wings, sometimes reduced or vestigial. The front wings, called Tegmina, are straight and thickened, while the hind wings are membranous.

5. Exhibits gradual metamorphosis, where nymphs closely resemble adults in essential features and habits.

Objective: The aim of this practical session is to explore the taxonomic features of the order Isoptera and classify its families.

Order: Isoptera (Iso = equal, ptera = wing) – Termites

Taxonomic Characteristics

1. Moderate-sized, social insects with thin skin, comprising various castes such as winged kings and queens, wingless kings and queens, workers, and soldiers.

2. Exhibits simple metamorphosis.

3. Mouthparts are of the typical biting and chewing type.

4. Wings are equal in size, long, narrow, membranous, and somewhat opaque.

5. Workers and soldiers of both sexes are wingless and sterile forms.

Objective: To explore the habits, habitats, and taxonomic features of the order Thysanoptera and the family Thripidae.

Order: Thysanoptera

Etymology: Thysano (fringed) + Ptera (wings) = Fringed-winged Insects (THRIPS)

Habitat: Terrestrial, commonly found in flowers

Habit: Phytophagous, feeding on plant material

Size: Minute to small, characterized by thin, slender elongated bodies

Taxonomic Characteristics

1. Antennae: Typically 6-10 segmented, with sensorial structures (cone like) on the 3rd or 4th segment.

2. Compound Eyes: Conspicuous, with 3-4 ommatidia in apterous forms and up to 150 in winged forms. Winged forms also exhibit 3 ocelli.

3. Mouthparts: Asymmetrical, lacking the right mandible. Adapted for lacerating, rasping, and sucking, with three stylets. The mouth cone, formed by the labrum, labium, and maxillae, extends ventrally between the fore coxae

Objective: To identify key characters of the order Neuroptera and explore the characteristics of the family Chrysopidae.

Order: Neuroptera

Etymology: Neuro (nerve) + Ptera (wings) = Wings with net-like patterns of veins

Common Members: Lacewings, Aphid Lions, Ant Lions, Alder Flies, Snakeflies

Key Features of Neuroptera

1. Neuroptera possess two pairs of similar-sized membranous wings with a complex, net-like pattern of veins.

2. They are relatively fragile insects and weak fliers.

3. Antennae are filiform, with or without a terminal club.

4. Both adults and larvae have chewing mouthparts, with larval mandibles being very strong and elongated. Some larval mouthparts are modified for piercing and sucking.

5. Larvae are compodiform and predaceous.

Objective: To understand the taxonomic characters and classification of the order Coleoptera, which includes beetles and weevils.

Order: Coleoptera (Coleos = sheath, Pteron = wing) Beetles and Weevils

Taxonomic Characteristics

1. Two pairs of wings, with the forewings thickened and hardened, forming protective covers called elytra, while the hind wings are membranous and protected by the elytra.

2. Both larvae and adults possess biting and chewing mouthparts.

3. Metamorphosis is complete.

4. Beetle larvae are commonly known as grubs. Snout beetle (weevil) grubs are legless (apodous).

Objective: To comprehend the fundamental taxonomic characteristics of the order Hymenoptera and its agriculturally significant families.

The order Hymenoptera displays remarkable diversity in its insect inhabitants. The term “Hymenoptera” originates from “Hymen” meaning membrane or the God of marriage, and “ptera” meaning wings.

Taxonomic Characters

1. Hymenopterans possess mandibulate mouthparts, where the labium and maxilla’s basal sections lie closely side by side, forming a sharp transverse fold near the basal third. In bees, these structures integrate to form a lapping tongue, representing a chewing and lapping type of mouthpart.

2. The thorax is specialized for efficient flight, featuring a collar-like pronotum, an enlarged mesothorax, and a small metathorax. The prothorax and metathorax are fused with the mesothorax.

History of Chemical Control, Insecticide Toxicology and Properties

History of pest control probably started when the first person swatted a mosquito or pulled off a tick, the battle for the control of our planet didn’t start until organized agriculture, when pests attacked the plants, and we grew to eat and threatened our very survival.

A pesticide is any substance or mixture of substances used to stop, kill, avoid, or lessen the effects of a pest (insects, mites, nematodes, weeds, rats, etc.). This includes insecticide, herbicide, fungicide, and many other substances used to control pests. Pesticide was defined in different ways at different times and in different places. But pesticide is still generally the same: it is a (mixed) substance that is poisonous and effective on target organisms but safe for non-target organisms and environments.

Chemical control, commonly known as pest control, is the use of chemicals to reduce insect populations. Herbicides, fungicides, insecticides, rodenticides, acaricides, nematodes, and fungicides are all examples of pesticides. Insecticides are a class of chemicals used to combat insect pests. A substance or combination of compounds used to kill, repel, or otherwise prevent insects is called an insecticide. When it comes to controlling pests, insecticides are most powerful tools available for management. They have a wide range of positive effects, including high efficiency, speed of healing, general applicability, adaptability to different settings, adaptability to shifting agronomic and ecological conditions, and low cost. When insect pest numbers approach or surpass the economic threshold, insecticides are the sole viable instrument for emergency action in pest management. The usage of pesticides, a widely used method, can be central to such a system. The use of chemical pesticides will remain pivotal in these initiatives. In many cases, chemical control of pests is the best option available. Some people’s view of pesticide use for pest management as an ecological sin is incorrect. Chemical pesticides are a reliable and useful tool for the biologist, so long as they are used in accordance with good ecological principles.

A bioassay, also known as a biological assay, is a scientific experiment used to quantify the impact of a substance on a living organism. According to Finney (1952), bioassay is defined as measurement of potency of any stimulus (physical, chemical, biological, physiological) by means of reactions which it produces in living matter. It is an essential procedure in insecticide development and the assessment of environmental pollutants, as well as the evaluation of the effects of interventions viz. pesticides and herbicides on the environment. In the field of biostatistics, a bioassay refers to a set of techniques used to determine the quantity or intensity of an agent or stimulus based on the response of the subject. Typically, many methods are employed to assess the strength or effectiveness of an insecticide by examining its impact on living organisms.

An insecticide is a pesticide used to kill or eliminate insect pests in agriculture, households, and industries. Judicious use of insecticides may be a factor in the increase of agricultural productivity, but by their nature of having high toxicity to non target organisms and capability to develop resistance through widespread use, most insecticides have high potential to significantly affect and alter ecosystems. Many are toxic to humans and animals (both domestic and wildlife), and can accumulate as concentrates in the food chain and water resources, giving rise to serious environmental contamination and pollution.

Formulation is a word that can be used in a lot of different ways, but at its core, it means putting things together in the right way, usually by following a formula. Insecticides come in different forms, which are called formulations. A formulation is just the way a product is used. The chemical or biological makeup of a pesticide and its active ingredient (also called the active substance) determine how it works on living things. Most of the time, the active ingredient is mixed with other things, and the product as it is sold will need to be weakened even more before it can be used. Formulation makes a drug easier to handle, store, and use. It can also have a big effect on how well it works and how safe it is.

Insecticides come in many different forms because the active ingredients vary in how easily they dissolve, how well they kill pests, and how easy they are to handle and move. The pesticide is made up of both active and non-active (used to be called “inert”) chemicals. The manufacturer will need to know the identity of the pest, as well as details about its feeding behavior, reproduction, and life cycle, in order to create an effective formulation. Manufacturers also take into account factors including surface and equipment type, runoff and drift rates, pest habits, and safety when formulating insecticides. Inactive materials (adjuvants/ additives) are often added to insecticides to make them stick to the application surface or spread out over leaves. There are solvents (liquids) that dissolve the active ingredient, carriers (liquids or solids) that aid in the delivery of the active ingredient, etc.. Boosting the efficacy of active ingredients requires additives, such as spreaders, stickers, wetting agents, compatibility agents, foaming agents, etc.

Introduction

Analysis of insecticide formulations are critical for the availability of quality insecticides in the market for ultimate benefit of farmers and ecosystem health. This chapter highlights the significance of comprehensive insecticide formulation analysis protocols, encompassing methods for determining active ingredient and assessing physical and chemical parameters. Employing advanced analytical techniques such as spectroscopy and chromatography for insecticide formulation analysis will eventually maintain the quality of insecticides for the sustainable management of pests.

In India, over 339 pesticides are registered that includes insecticides, fungicides, herbicides (DPPQS, 2024). The current market of non-genuine insecticide is INR 3,200 crores (USD 525 Million) which constitutes 25 per cent by value and 30 per cent by volume of the total domestic market of agrochemicals in India as per Industry reports, primary interviews, news articles and Tata Strategic analysis (FICCI, 2015). Monitoring registration and regulation of insecticides is governed by the Insecticide Management Bill 2020, which replaced the Insecticide Act 1968 (DPPQS, 2023). The Insecticide Act of 1968 established the Central Insecticide Laboratory, Faridabad, under section 16 with two regional insecticide testing laboratories at Chandigarh and Kanpur (DPPQS, 2023). Current Quality Control of Insecticides in States/UTs during the last five years shows that 68078 insecticide samples were analysed (DPPQS, 2023). In the beginning, these laboratories involved in analysing insecticide samples drawn by any officer or the body authorized by the Central or State Governments and submit certificates of analysis to the concerned authority. Regional Pesticide Testing Laboratories (RPTLs) had a huge target of analysis of 1550 samples per annum that necessitated the establishment of 71 State Pesticide Testing Laboratories (SPTL) spread across India of which 14 are NABL accredited (DPPQS, 2023).

Insecticide classification majorly divided into three categories. A. based on chemical group, B. mode of entry in the insect, C. based on toxicity.

A. Classification of Insecticides based on chemical group

Historians have traced the use of pesticides to the time of Homer around 1000 B.C. earliest records of insecticide use pertain to the burning of “brimstone” (Sulfur) as a fumigant. Pliny the Elder (A.D. 23-79) recorded most of the earlier insecticide uses in his Natural History and included among these was the use of gall from a green lizard to protect apples from worms and rot. Later, a variety of materials used viz., extracts of pepper and tobacco, soapy water, whitewash, vinegar, turpentine, fish oil, brine, lye and many others. At the beginning of World War II (1940), insecticide selection was limited to several inorganic compounds, arsenicals, petroleum oils, nicotine, pyrethrum, rotenone, sulfur, hydrogen cyanide gas, and cryolite. It was during World War II that opened the Chemical Era with the introduction of a totally new concept of insect control.

The way a chemical moves, persists, and behaves in its surroundings is known as its behaviour. A chemical’s behaviour will dictate both its residual properties and field efficacy. The behaviour of insecticides is determined by their chemical and physical characteristics as well as the interaction of environmental elements. Our capacity to comprehend and forecast how insecticides will behave in the environment will determine our ability to keep utilizing insecticides.

Important features of systemic insecticides

1. They are not susceptible to wash off by rain

2. By virtue of their movement inside plants, they can afford to protection to regions where they have not been sprayed

3. They are often been transported towards region of growth

4. Since they have very weak contact action, safe to beneficial organism.

Pesticide use in agriculture has evolved at several stages in the last few decades. Pesticides, as defined by the FAO, are any substance or mixture of substances intended to prevent, destroy, or control any pest, including vectors of human or animal disease, unwanted species of plants or animals causing harm during or otherwise interfering with the production, processing, storage, transport, or marketing of food, agricultural commodities, wood and wood products, or animal feedstuffs, or substances that may be administered to animals. A plant growth regulator, defoliant, desiccant, or agent used to thin or prevent premature fruit fall, as well as substances applied to crops before or after harvest to prevent them from deteriorating during storage and transportation, are included in this category.

Today’s agrochemistry has a massive challenge: ensuring the availability of high quality active ingredients to enable long-term control of pest species, weeds, and agricultural diseases. The differential uptake and transfer of the active ingredient by target and non-target organisms can contribute to diverse biological activity.

Insecticide mode of action is divided in to four major chapters 1. Nerve & Muscle 2. Growth & development 3. Respiration & Energy production 4. Metabolic process 5. Unknown or Non-Specific (multisite inhibitors) (Source: IRAC). To understand the mode of action of insecticides, it is necessary to understand the function of nervous system and how it works in insect. The nervous system functions transmits information throughout the body. This system has three components: 1) Peripheral nervous system (PNS) to receive and transmit incoming signals (taste, smell, sight, sound, and touch) and to transmit outgoing signals to the muscles and other organs, effectively communicating them how to respond, and 2) Central nervous system (CNS) to interpret the signals and coordinate the body’s responses and movements. 3) Visceral or sympathetic nervous system (VNS) directly connected with the brain that supplies nerves to the anterior part of the alimentary canal (foregut and midgut), heart, and spiracles. Some additional nerves arise from posterior compound ganglion of ventral nerve cord (VNC) which supply nerves to the posterior part of gut and reproductive system.

Synergists are chemicals that significantly increase the toxicity of an insecticide while being nearly non-toxic on their own. Thus, non-toxic chemicals that contribute to the increased toxicity of insecticides are referred to as synergists. Many chemical substances have the potential to synergize with poisons. Some enzyme inhibitors work well synergistically by inhibiting enzymes that metabolize pesticides, particularly in insecticide-resistant strains. When mixed with other insecticides, some insecticides increase the toxicity of the latter at non-toxic dosages. When a mixture is more harmful than expected based on the sum of its separate efficacies when administered alone, the interaction between substances is known as synergy. Antagonistic interactions among components reduce a mixture’s efficacy.

Synergism can also develop between two or more poisons. Several statistical methods have been proposed to quantify the synergy of both non-toxic and hazardous substances. Toxin interactions are assessed using bioassays, which involve mixing toxicants (two or more) in a specific ratio. The combination is then used to prepare serial dilutions. Alternatively, the poisons can be supplied sequentially in the same amounts as in the mixture. Bioassays are also used to determine the dose-mortality response of each toxin on the same insect strain. The data are subjected to probit analysis, and the toxin interactions can be evaluated using the statistical methods listed below.

Insecticide resistance is a growing concern for those who need insecticides for medical, veterinary, and agricultural control of insect pests. In response to the introduction of DDT resistance in 1947, the incidence of resistance has increased annually by an alarming amount. Resistance is “the inherited ability of a strain of some organism to survive doses of a toxicant that would kill the majority of individuals in a normal population of the same species” (WHO, 1957).

As a result of continued insecticide application, the proportion of resistant insects increases compared to that of susceptible and the population becomes increasingly difficult to control

Above photograph theoretical example illustrating the increase of insecticide resistance levels in a pest population. Some individuals (black) with genetic traits allowing them to survive insecticide applications can reproduce; if the selection pressure is frequent, they easily become the preponderant part of the population (Fig. 1).

An adaptation to a pesticide leads to reduced susceptibility to it among the pest population targeted by that pesticide. In nature, pests develop resistance to chemicals through natural selection. In the most resistant organisms, their genetic traits are passed on to their descendants. Since 1945, at least 500 species of pests have developed resistance to pesticides (Anonymous, 2007), but other sources estimate as many as 1000 species (Miller, 2004).