Other names used, but no longer in vogue, are organic phosphates, phosphorus insecticides, nerve gas relatives, and phosphoric acid esters. All organophosphates are derived from one of the phosphorus acids, and as a class are generally the most toxic of all pesticides to vertebrates.
Because of the similarity of OP chemical structures to the "nerve gases," their modes of action are also similar. Their insecticidal qualities were first observed in Germany during World War II in the study of the extremely toxic OP nerve gases sarin , soman, and tabun. Initially, the discovery was made in search of substitutes for nicotine, which was heavily used as an insecticide but in short supply in Germany.
The OPs have two distinctive features: they are generally more toxic to vertebrates than other classes of insecticides, and most are chemically unstable or nonpersistent. It is this latter characteristic that brought them into agricultural use as substitutes for the persistent organochorines. Mode of action The OPs work by inhibiting certain important enzymes of the nervous system, namely cholinesterase ChE.
The enzyme is said to be phosphorylated when it becomes attached to the phosphorous moiety of the insecticide, a binding that is irreversible. Classification All OPs are estersof phosphorus having varying combinations of oxygen, carbon, sulfur and nitrogen attached, resulting in six different subclasses: phosphates, phospho-nates, phosphorothioates, phosphorodithioates, phosphorothiolates and phosphoramidates.
These subclasses are easily identified by their chemical names. The OPs are generally divided into three groups-- aliphatic, phenyl , and heterocyclic derivatives. The aliphatic OPs are carbon chain-like in structure. The phenyl OPs are generally more stable than the aliphatics, thus their residues are longer lasting. The first phenyl OP brought into agriculture was parathion ethyl parathion in The term heterocyclic means that the ring structures are composed of different or unlike atoms, e.
The first of this group was diazinon introduced in These few materials have very low toxicity to insects and are used only as acaricides miticides. They contain two phenyl rings, resembling DDT, with sulfur in place of carbon as the central atom. The carbamate insecticides are derivatives of carbamic acid as the OPs are derivatives of phosphoric acid. And like the OPs, their mode of action is that of inhibiting the vital enzyme cholinesterase ChE. More of it has been used worldwide than all the remaining carbamates combined.
Two distinct qualities have made it the most popular carbamate: its very low mammalian oral and dermal toxicity and an exceptionally broad spectrum of insect control. Carbamates more recently introduced include primicarb, indoxacarb registered in , alanycarb and furathiocarb.
Mode of action Carbamates inhibit cholinesterase ChE as OPs do, and they behave in almost identical manner in biological systems, but with two main differences. Some carbamates are potent inhibitors of aliesterase miscellaneous aliphatic esterases whose exact functions are not known , and their selectivity is sometimes more pronounced against the ChE of different species.
Second, ChE inhibition by carbamates is reversible. When ChE is inhibited by a carbamate, it is said to be carbamylated , as when an OP results in the enzyme being phosphorylated. In insects, the effects of OPs and carbamates are primarily those of poisoning of the central nervous system, since the insect neuromuscular junction is not cholinergic, as in mammals. The only cholinergic synapses known in insects are in the central nervous system. The chemical neuromuscular junction transmitter in insects is thought to be glutamic acid.
The formamidines comprise a small group of insecticides. Their current value lies in the control of OP- and carbamate-resistant pests. Mode of action Formamidine poisoning symptoms are distinctly different from other insecticides. Their proposed action is the inhibition of the enzyme monoamine oxidase, which is responsible for degrading the neurotransmitters norepinephrine and serotonin.
This results in the accumulation of these compounds, which are known as biogenic amines. Affected insects become quiescent and die. The basic dinitrophenol molecule has a broad range of toxicities--as herbicides, insecticides, ovicides, and fungicides. Dinocap is an effective miticide and was very heavily used as a fungicide for the control of powdery mildew fungi. Because of the inherent toxicity of the dinitrophenols, they have all been withdrawn. Mode of action Dinitrophenols act by uncoupling or inhibiting oxidative phosphorylation, which basically prevents the formation of the high-energy phosphate molecule, adenosine triphosphate ATP.
The organotins are a group of acaricides that double as fungicides. Mode of action These tin compounds inhibit oxidative phosphorylation at the site of dinitrophenol uncoupling, preventing the formation of the high-energy phosphate molecule adenosine triphosphate ATP.
These trialkyl tins also inhibit photophosphorylation in chloroplasts, the chlorophyll-bearing subcellular units and could therefore serve as algicides. Natural pyrethrum has seldom been used for agricultural purposes because of its cost and instability in sunlight.
In recent decades, many synthetic pyrethrin-like materials have become available. They were originally referred to as synthetic pyrethroids. Currently, the better nomenclature is simply pyrethroids. These are stable in sunlight and are generally effective against most agricultural insect pests when used at the very low rates of 0.
The pyrethroids have an interesting evolution, which is conveniently divided into four generations. Its synthesis was very complex, involving 22 chemical reactions to reach the final product. These became the first agricultural pyrethroids because of their exceptional insecticidal activity 0. They were virtually unaffected by ultraviolet in sunlight, lasting days as efficacious residues on crop foliage.
The fourth and current generation, is truly exciting because of their effectiveness in the range of 0. All of these are photostable, that is, they do not undergo photolysis splitting in sunlight. And because they have minimal volatility they provide extended residual effectiveness, up to 10 days under optimum conditions.
Mode of action The pyrethroids share similar modes of action, resembling that of DDT, and are considered axonic poisons. They apparently work by keeping open the sodium channels in neuronal membranes. There are two types of pyrethroids.
Type I, among other physiological responses, have a negative temperature coefficient, resembling that of DDT. Type II, in contrast have a positive temperature coefficient, showing increased kill with increase in ambient temperature. Pyrethroids affect both the peripheral and central nervous system of the insect.
They initially stimulate nerve cells to produce repetitive discharges and eventually cause paralysis. Such effects are caused by their action on the sodium channel, a tiny hole through which sodium ions are permitted to enter the axon to cause excitation. The stimulating effect of pyrethroids is much more pronounced than that of DDT.
The nicotinoids are a newer class of insecticides with a new mode of action. They have been previously referred to as nitro-quanidines , neonicotinyls, neonicotinoids, chloronicotines, and more recently as the chloronicotinyls.
Just as the synthetic pyrethroids are similar to and modeled after the natural pyrethrins, so too, are the nicotinoids similar to and modeled after the natural nicotine. Imidacloprid was introduced in Europe and Japan in and first registered in the U.
It is currently marketed as several proprietary products worldwide, e. Very possibly it is used in the greatest volume globally of all insecticides. Imidacloprid is a systemic insecticide, having good root-systemic characteristics and notable contact and stomach action. It is used as a soil, seed or foliar treatment in cotton, rice cereals, peanuts, potatoes, vegetables, pome fruits, pecans and turf, for the control of sucking insects, soil insects, whiteflies, termites, turf insects and the Colorado potato beetle, with long residual control.
Imidacloprid has no effect on mites or nematodes. Mode of action The nicotinoids act on the central nervous system of insects, causing irreversible blockage of postsynaptic nicotinergic acetylcholine receptors See also Nicotine under the Botanicals. Spinosad is a fermentation metabolite of the actinomycete Saccharopolyspora spinosa , a soil-inhabiting microorganism. It has a novel molecular structure and mode of action that provide excellent crop protection typically associated with synthetic insecticides, first registered for use on cotton in Spinosad is a mixture of spinosyns A and D thus its name, spinosAD.
It is particularly effective as a broad-spectrum material for most caterpillar pests at the astonishing rates of 0. It has both contact and stomach activity against lepidopteran larvae, leaf miners, thrips, and termites, with long residual activity.
Crops registered include cotton, vegetables, tree fruits, ornamentals and others. Mode of action Spinosad acts by disrupting binding of acetylcholine in nicotinic acetylcholine receptors at the postsynaptic cell Salgado VL See also Nicotine under the Botanicals. It is a systemic material with contact and stomach activity.
Fipronil is used for the control of many soil and foliar insects, e. It is also used for seed treatment and formulated as baits for cockroaches, ants and termites. Fipronil is effective against insects resistant or tolerant to pyrethroid, organophosphate and carbamate insecticides. Mode of action Fipronil blocks the g-aminobutyric acid- GABA regulated chloride channel in neurons, thus antagonizing the "calming" effects of GABA, similar to the action of the Cyclodienes see page 3.
It is used on cotton and experimentally on corn, soybeans, vegetables, tree and vine crops, and ornamentals to control whitefly, thrips, caterpillars, mites, leafminers, aphids, and Colorado potato beetle. It has ovicidal activity on some species. EPA took the unusual step of refusing to register chlorfenapyr in for cotton insect control because of potential hazards to birds.
However, labels for greenhouse ornamentals were granted in Mode of action Chlorfenapyr is an "uncoupler" or inhibitor of oxidative phosphorylation, preventing the formation of the crucial energy molecule adenosine triphosphate ATP See also Dinitrophenols. The original pyrazoles were tebufenpyrad and fenpyroximate not illustrated. These were designed primarily as non-systemic contact and stomach miticides, but do have limited effectiveness on psylla, aphids, whitefly, and thrips. Mode of action Their mode of action is that of inhibiting mitochondrial electron transport at the NADH-CoQ reductase site, leading to the disruption of adenosine triphosphate ATP formation, the crucial energy molecule.
It is a selective contact insecticide and miticide, also effective against thrips, aphids, whiteflies and leafhopprs. Registrations are for pome fruits, almonds, citrus, ornamentals and greenhouse ornamentals. Pyridaben provides exceptionally long residual control, and rapid knockdown at a broad range of temperatures. Mode of action Pyridaben is a metabolic inhibitor that interrupts mitochondrial electron transport at Site 1, similar to the Quinazolines, below.
Fenazaquin is a contact and stomach miticide. It has ovicidal activity, gives rapid knockdown, and controls all stages of mites. Not yet registered in the U. Mode of action Fenazaquin inhibits mitochondrial electron transport at Site 1, similar to the Pyridazinones, above. Benzoylureas are an entirely different class of insecticides that act as insect growth regulators IGRs.
Rather than being the typical poisons that attack the insect nervous system, they interfere with chitin synthesis and are taken up more by ingestion than by contact. Their greatest value is in the control of caterpillars and beetle larvae. Benzoylureas were first used in Central America in , to control a severe, resistant leafworm complex Spodoptera spp. The withdrawal of the ovicide chlordimeform made their control quite difficult due to their high resistance to almost all insecticide classes, including the pyrethroids.
Among the newer benzoylureas only hexaflumuron and novaluron have been registered by EPA. The only other benzoylurea registered in the U. It was first registered in for gypsy moth, cotton boll weevil, most forest caterpillars, soybean caterpillars, and mushroom flies, but now with a much broader range of registrations. It is selective toward Dipterous species and used for the control of leafminers in vegetable crops and ornamentals, and fed to poultry or sprayed to control flies in manure of broiler and egg producing operations, and incorporated into compost of mushroom houses for fungus gnats.
Mode of action The benzoylureas act on the larval stages of most insects by inhibiting or blocking the synthesis of chitin, a vital and almost indestructible part of the insect exoskeleton.
Typical effects on developing larvae are the rupture of malformed cuticle or death by starvation. Adult female boll weevils exposed to diflubenzuron lay eggs that do not hatch.
And, mosquito larvae control can be achieved with as little as 1. Botanical insecticides are of great interest to many, for they are natural insecticides, toxicants derived from plants. Historically, the plant materials have been in use longer than any other group, with the possible exception of sulfur.
Tobacco, pyrethrum, derris, hellebore, quassia, camphor, and turpentine were some of the more important plant products in use before the organized search for insecticides began in the early s. In recent years the term biorational has been put into play by the EPA.
There are similarities and differences between the terms botanical and biorational. We include a section on the biorationals below and will address the overlaps in that section. Botanical insecticide use in the U. Pyrethrum is now the only classical botanical of significance in use. Some newer plant-derived insecticides that have come into use are referred to as florals or scented plant chemicals and include, among others, limonene, cinnamaldehyde and eugenol.
In addition, there is azadirachtin from the neem tree which is used in greenhouse and on ornamentals. Pyrethrum is extracted from the flowers of a chrysanthemum grown in Kenya and Ecuador. It is one of the oldest and safest insecticides available. The ground, dried flowers were used in the early 19th century as the original louse powder to control body lice in the Napoleonic Wars. Pyrethrum acts on insects with phenomenal speed causing immediate paralysis, thus its popularity in fast knockdown household aerosols.
However, unless it is formulated with one of the synergists , most of the paralyzed insects recover to once again become pests. Mode of action Pyrethrum is an axonic poison, as are the synthetic pyrethroids and DDT. Axonic poisons are those that in some way affect the electrical impulse transmission along the axons, the elongated extensions of the neuron cell body. Pyrethrum and some pyrethroids have a greater insecticidal effect when the temperature is lowered, a negative temperature coefficient, as does DDT.
They affect both the peripheral and central nervous system of the insect. Pyrethrum initially stimulates nerve cells to produce repetitive discharges, leading eventually to paralysis. These effects are produced in insect nerve cord, which contains ganglia and synapses, as well as in giant nerve fiber axons.
Nicotine is extracted by several methods from tobacco, and is effective against most all types of insect pests, but is used particularly for aphids and caterpillars--soft bodied insects. Nicotine is an alkaloid, a chemical class of heterocyclic compounds containing nitrogen and having prominent physiological properties.
Other well-known alkaloids that are not insecticides are caffeine coffee, tea , quinine cinchona bark , morphine opium poppy , cocaine coca leaves , ricinine a poison in castor oil beans , strychnine Strychnos nux vomica , coniine spotted hemlock, the poison used by Socrates , and, finally LSD a hallucinogen from the ergot fungus attacking grain.
Mode of action Nicotine action is one of the first, classic modes of action identified by pharmacologists. Drugs that act similarly to nicotine are said to have a nicotinic response. In insects the same action is observed, but only in the central nervous system ganglia. It is both a stomach and contact insecticide and used for the last century and a half to control leaf-eating caterpillars, and three centuries prior to that in South America to paralyze fish, causing them to surface and be easily captured.
Today, rotenone is used in the same way to reclaim lakes for game fishing. Used on a prescribed basis, it eliminates all fish, closing the lake to reintroduction of rough species. It is a selective piscicide in that it kills all fish at dosages that are relatively nontoxic to fish food organisms, and is degraded rapidly.
Limonene or d -Limonene is the latest addition to the botanicals. Limonene belongs to a group often called florals or scented plant chemicals. Extracted from citrus peel, it is effective against all external pests of pets, including fleas, lice, mites, and ticks, and is virtually nontoxic to warm-blooded animals.
Two other recently introduced floral products are eugenol Oil of Cloves and cinnamaldehyde derived from Ceylon and Chinese cinnamon oils.
They are used on ornamentals and many crops to control various insects. Mode of action Its mode of action is similar to that of pyrethrum. It affects the sensory nerves of the peripheral nervous system, but it is not a ChE inhibitor. Neem oil extracts are squeezed from the seeds of the neem tree and contain the active ingredient azadirachtin , a nortriterpenoid belonging to the lemonoids.
Azadirachtin has shown some rather sensational insecticidal, fungicidal and bactericidal properties, including insect growth regulating qualities. Mode of action Azadirachtin disrupts molting by inhibiting biosynthesis or metabolism of ecdysone, the juvenile molting hormone.
Synergists are not in themselves considered toxic or insecticidal, but are materials used with insecticides to synergize or enhance the activity of the insecticides.
The first was introduced in to increase the effectiveness of pyrethrum. Since then many materials have appeared, but only a few are still marketed. Synergists are found in most all household, livestock and pet aerosols to enhance the action of the fast knockdown insecticides pyrethrum, allethrin, and resmethrin, against flying insects.
Current synergists, such as piperonyl butoxide, contain the methylenedioxyphenyl moiety, a molecule found in sesame oil and later named sesamin. The effects they have will depend on the medium in which they occur.
The bioavailability, uptake, and toxicity of insecticides during these exposures will depend on factors such as temperature, suspended sediment concentrations, and dissolved organic carbon concentrations. Insecticides may affect aquatic biota via several different modes of action, and in many cases mode of action will vary with the type of insecticide.
For example, organophosphates and carbamates increase cholinesterase inhibition; pyrethroids disrupt the functioning of sodium channels in neuronal membranes. Other insecticides can regulate growth, or act as gamma aminobutyric acid GABA blockers.
These different modes of action all may contribute to decreased condition, decreased growth, altered behavior, and increased susceptibility to other stressors in affected biota. For example, exposure to increased insecticide concentrations may lead to elevated tissue concentrations, respiratory distress, and changes in development. Possible changes in behavior include increased invertebrate drift and increased coughing, yawning, nudge and nip, fin-flicking, and jerk behaviors in fish.
Ultimately, these effects may result in increased mortality, decreased reproductive success, and changes in population and community structure and ecosystem function. For example, macroinvertebrates may be especially susceptible to insecticides, so they may decrease in abundance and richness.
Sensitive life stages may decrease, while tolerant taxa and life stages become more prevalent. This section presents an annotated bibliography of references providing information on stressor-response relationships for insecticides, as well as general background on insecticide properties. This is not meant to be a comprehensive bibliography of references dealing with insecticides, but rather is meant to highlight a few references that may be especially useful, but not yet covered in the ECOTOXicology knowledgebase ECOTOX Database.
In addition, the U. EPA has published water quality criteria documents on many insecticides, which provide helpful literature reviews. This report presents evaluations of concentrations of pesticides in streams and ground water and their potential effects based on findings for the first decadal cycle of NAWQA. This database has toxicity data for pesticides across many species, and provides a good starting point for finding pesticide use, occurrence, and effects data on the web.
In this study, the impact of insecticides associated with rainfall-induced surface runoff form arable lands on invertebrates was examined. It was found that agricultural runoff alters the dynamics of macroinvertebrates in streams. This study looked at the effects of insecticides on various aquatic communities. Effects differed based on species and type of pesticide underscoring the importance of looking at both direct and indirect effects.
The study looked at the acute toxicity of pyrethroid insecticides to aquatic insects. The authors found that aquatic insects were generally more susceptible than terrestrial insects.
This is a recent reference for mechanistic health and environmental toxicity information for pesticides, including herbicides and insecticides. Skip to main content. Contact Us. Table 1. Usually broad-spectrum insecticides that have been taken out of use. Organophosphate Cause acetylcholinesterase AChE inhibition and accumulation of acetylcholine at neuromuscular junctions causing rapid twitching of voluntary muscles and eventually paralysis.
A broad-range insecticide, generally the most toxic of all pesticides to vertebrates. Organosulfur Exhibit ovicidal activity i. Used only against mites with very low toxicity to other organisms. Carbamates Cause acetylcholinesterase AChE inhibition leading to central nervous system effects i.
Has very broad spectrum toxicity and is highly toxic to fish. Formamidines Inhibit the enzyme monoamine oxidase that degrades neurotransmitters causing an accumulation of these compounds; affected insects become quiescent and die. Used in the control of OP and carbamate-resistant pests.
Dinitrophenols Act by uncoupling or inhibiting oxidative phosphorylation preventing the formation of adenosine triphosphate ATP. All types have been withdrawn from use. Organotins Inhibit phosphorylation at the site of dinitrophenol uncoupling, preventing the formation of ATP. Used extensively against mites on fruit trees and formerly used as an antifouling agent and molluscacide; very toxic to aquatic life. Pyrethroids Acts by keeping open the sodium channels in neuronal membranes affecting both the peripheral and central nervous systems causing a hyper-excitable state.
Symptoms include tremors, incoordination, hyperactivity and paralysis. Effective against most agricultural insect pests; extremely toxic to fish. Nicotinoids Act on the central nervous system causing irreversible blockage of the postsynaptic nicotinergic acetylcholine receptors.
Used in the control of sucking insects, soil insects, whiteflies, termites, turf insects and the Colorado potato beetle. Generally have low toxicity to mammals, birds and fish. Spinosyns Acts by disrupting binding of acetylcholine in nicotinic acetylcholine receptors at the postsynaptic cell. Effective against caterpillars, lepidopteran larvae, leaf miners, thrips and termites. Regarded for its high level of specificity. Effective against psylla, aphids, whitefly and thrips.
Results of testing on one type fipronil indicate no effects on the clams, oysters or fish, with marginal effects on shrimp. Pyridazinones Interrupt mitochondrial electron transport at Site 1; mainly used as a miticide; display toxicity to aquatic arthropods and fish. Quinazolines Acts on the larval stages of most insect by inhibiting or blocking the synthesis of chitin in the exoskeleton. Developing larvae exhibit rupture of the malformed cuticle or death by starvation; not registered in U.
Botanicals Depending upon the type can have various effects: Pyrethrum — affects both the central and peripheral nervous systems, stimulating nerve cells to produce repetitive discharges and eventually leading to paralysis. Commonly used to control lice. Nicotine — mimics acetylcholine Ach in the central nervous system ganglia, causing twitching, convulsions and death. Used most to control aphids and caterpillars. Rotenone — acts as a respiratory enzyme inhibitor.
Used as a piscicide that kills all fish at doses non-toxic to fish food organisms. Limonene — affects the sensory nerves of the peripheral nervous system. Used to control fleas, lice, mites and ticks, while remaining virtually non-toxic to warm-blooded animals and only slightly toxic to fish.
Commonly used against moth and butterfly larvae. Antibiotics Act by blocking the neurotransmitter GABA at the neuromuscular junction; feeding and egg laying stop shortly after exposure while death may take several days.
Most promising use of these materials is the control of spider mites, leafminers and other difficult to control greenhouse pests. Fumigants Act as narcotics that lodge in lipid-containing tissues inducing narcosis, sleep or unconsciousness; pest affected depends on particular compound.
Inorganics Mode of action is dependent upon type of inorganic: may uncouple oxidative phosphorylation arsenicals , inhibit enzymes involved in energy production, or act as desiccants. Pest group depends on compound e. Biorational Grouped as biochemicals hormones, enzymes, pheromones natural agents such as growth regulators or microbials viruses, bacteria, fungi, protozoa and nematodes.
Act as either attractants, growth regulators or endotoxins; known for very low toxicity to non-target species. Benzoylureas Act as insect growth regulators by interfering with chitin synthesis. Greatest value is in the control of caterpillars and beetle larvae but is also registered for gypsy moth and mushroom fly. Some types are known for their impacts on invertebrates reduced emergent species and early life stages of sunfish reduced weight Boyle et al.
From Radcliffe et al. Literature Reviews This section presents an annotated bibliography of references providing information on stressor-response relationships for insecticides, as well as general background on insecticide properties. Geological Survey. Circular Liess M, Shulz R Linking insecticide contamination and population response in an agricultural stream.
Environmental Toxicology and Chemistry 18 9 Relyea RA The impact of insecticides and herbicides on the biodiversity and productivity of aquatic communities. Ecological Applications 15 2 Siegfried BD Comparative toxicity of pyrethroid insecticides to terrestrial and aquatic insects.
Environmental Toxicology and Chemistry References Alkahem HF Effects of lethal and sublethal concentrations of lindane on the behavior and energy reserves of the freshwater fish, Oreochromus niloticus. Journal of King Saud University: Science Environmental Toxicology and Chemistry 20 12 Beketov MA, Liess M Potential of eleven pesticides to initiate downstream drift of stream macroinvertebrates. Nglish: Translation of insecticide for Spanish Speakers.
Britannica English: Translation of insecticide for Arabic Speakers. Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!
Log in Sign Up. Save Word. Definition of insecticide. Examples of insecticide in a Sentence Recent Examples on the Web Spraying with an insecticide is not usually necessary and will also kill other beneficial insects. Stewart, Chron , 17 Sep. First Known Use of insecticide , in the meaning defined above. History and Etymology for insecticide International Scientific Vocabulary. Learn More About insecticide. Time Traveler for insecticide The first known use of insecticide was in See more words from the same year.
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