Inorganics and Botanical Insecticide

INORGANIC INSECTICIDES

Arsenic compounds:

In an arsenical compound, the total arsenic content and the water soluble arsenic content are of importance, the water solubility of arsenic may result in entering the foliage and causing burning injury to plants, and hence water insoluble compounds are preferred for insect control. Arsenates are more stable and safe for application on plants then arsenites. Arsenites are mainly used in poison baits since they are phytotoxic. However arsenates are less toxic to insects then arsenites. In insects arsenates cause regurgitation, torpor (sluggishness) and quiescence. Disintegration of epithelial cells of the midgut and clumping of the chromatin of the nuclei are the effects noticed in poisoned insects. Slow decrease in oxygen consumption is also evident and kill of the insect is primarily due to the inhibition of respiratory enzymes. Water soluble arsenic causes wilting followed by browning and shriveling of the tissue.

1. Calcium arsenate: It was first used by about 1906 as an insecticide. It is a white flocculent power, formulated as a dust of 25 to 30% metallic arsenic equivalent. Dosage – Calcium arsenate at 0.675 to 1.350 kg with equal quantity of slaked lime in 450 litres of water. LD50.for mammals oral – 35 to 100. Being a stomach poison it was mainly used for control of leaf eating insects.

2. Lead arsenate: It was first used as in insecticide in 1892 for the control of gypsy moth. It is a stomach poison with little contact action LD50.for rat oral 10-100, dermal 2400 mg/kg. . It is rarely used as dust. 450 g to 1800 g of load arsenate is diluted with 200-240 litres of water. An equal quantity of hydrated lime is some time added to prevent phytotoxicity to tender foliage. In baits it is used at 450 or900 g in 1200 g to 45000 g of carrier such as wheat bran or rice husk respectively.

3. Arsenite: Paris green:It is a double salt of copper acetate and copper arsenite. It was first used in 1867 for the control of Colorado potato beetle, Leptinotarsa decemlineata. It is now used as bait for the control of slugs. LD50for rat oral- 22 mg/kg.Very good against termites.

Flourine Compounds: These compounds were used since 1890. They are principally stomach poisons and to a limited extent contact poisons. The kill is more rapid than that of arsenicals. Their insecticidal properties are related to the fluorine content and solubility in the digestive juices of insect. Flouride poisoning produces spasms, regurgitation, flaccid paralysis and death.

1. Sodium fluoride: It is a white power. Available in 93 to 99% purity in commercial products. It is highly phytotoxic and used in poison baits used exclusively against cockroaches, earwigs, cutworms, grasshoppers etc.

Other inorganic compounds

1. Sulphur: It is primarily fungicide and acaricide. Formulated as fine dust (90 to 95% a.i with 10% inert material. It is also formulated as wettable powders. Effectiveness increases with fineness of sulphur particles.

2. Lime sulphur: Aqueous solution of calcium polysulphide. It is prepared by sulphur solution in calcium hydroxide suspension, preferably under pressure in the absence of air and is used against scales, mites, aphids besides powdery mildew.

Properties

§ Affect nervous system causing excitement at lower doses and paralysis at higher concentration.

§            Not phytoloxic

§            Leave no harmful side effects.

§            Mighly toxic to mammals.

§ Disappear rapidly from the treated surface.So can be used safely before harvest of the produce.

Insecticides of plant origin (Botanical Pesticides)

The insecticides of plant origin extracted from seeds, flowers, leaves, stem and roots, are termed as botanical insecticides. Insecticides of plant origin unlike synthetic organic insecticides are safer to use but since they are expensive and lack residual toxicity, their use has been limited in the country.

In nature more than, 2400 plant species are reported to have pesticidal properties. The important families having pesticidal properties are

Plant family	No. of plant having pesticidal property
Meliaceae	> 500
Myrtaceae	72
Asteraceae	70
Euphorbiaceae	65
Leguminosae	60
Fabaceae	55

1) Neem (Azadirachta indica)

Perennial tree distributed in tropical, subtropical, semi-arid and arid zones. It posses medicinal, insecticidal, insect repellent, antifeedant, growth regulatory, nematicidal and antifungal properties. Neem seed extract and oil contains a number of components such as Azadirachtin, salannin, nimbin, epinimbin nimbidin that gives insecticidal, insect repellent, ovicidal, Antifeedant and growth regulator characters. Azadiractitin disrupts moulting by antagonizing the insect hormone ecdysone.Azadiractitin Acute oral LD50 for rat is 5000mg/kg, Acute dermal for rabbit is >2000mg/kg.

Preparation of Neem Seed Kernel Extract (NSKE 5%): Take 50 g of powdered neem seed kernels soak it in one litre of water for 8 hours and stir the contents often. Squeeze the soaked material repeatedly for better extraction of the azadirachtin in the aquous suspension. Filter the contents through muslin cloth. Make the filtrate to one litre. Add 1ml teepol or triton or sandovit or soap water (2%) and spray.

Prepartion of Neem Cake Suspension

Soak one kilogram of neem cake in 5 liters of water for 2 days and filter It through muslin cloth. Dissolve 200 g of soft soap in the filtrate and make upto 10 L of water before spraying. This controls tobacco cutworm, leaf miners of citrus, groundnut, tomato and beans etc. Dried powder of neem leaves are used against stored grain insect pests. Leaf extracts showed insecticidal property against,Plutella xylostella,Aproaerema modicella; Spodoptera litura etc. Desert locust Schistocerca gregaria avoids feeding on neem leaves. Neem leaves are found as attractants to white grub Holotrichia adults. Neem seed/ kernel extract showed insecticidal properties against a number of sucking pest. Neem oil can be used against storage insect pests @ 1 to 2% and field insects @ (0.2 -0.4%, 1 to 2% 5% or 10% neem oil). Neem products are safer to honey bees, parasitoids, predators.

Commercial formulations of neem are available in 10000 ppm, 1500 ppm and 300 ppm the market. Some of the neem formulations are Margosan, Neemark, Neemrich, Achook, Bioneem, Neemazal, Neemax, Nimbicidine,Vepacide, Margocide , Neemgold etc

2) Nicotine: Nicotine is found in the leaves of Nicotiana tabacum and N.rusticafrom 2%

to 14%.Nicotine sulphate has been mainly used as a contact insecticide with marked fumigant action in the control of sucking insect’sviz., aphids, thrips, psyllids, leafminers and jassids. Nicotine sulphate is more stable and less volatile. It is a nerve poison being highly toxic when absorbed through the cuticle taken in through the tracheae or when ingested. It affects the ganglian blocking conduction at higher levels. Nicotine sulphate containing 40% alkaloid, is safer and is more convenient to use and the free alkaloid is liberated by the addition of soap lime or ammonium hydroxide to the spray solution. Dust formulation of nicotine sulphate releases nicotine in the presence of moisture. It is also used in aerosols. Tobacco decoction, useful for controlling aphids, Thrips etc. can be prepared by boiling 1kg of tobacco waste in 10lts of water for 30 minutes or steep it in cold water for a day. Then make it up to 30 litres and add about 90gm of soap. Addition of soap improves wetting, spreading and killing properties. Nicotine does not leave any harmful residue on treated surface. LD50for rat oral- 50-60 mg/kg.

3) Rotenone: It is extracted from the roots of Derris plant which many contain 4 to 11% rotenone depending on the variety. Though rotenone is reported from 68 species of leguminous plants, principal commercial sources are Derris ellipticaD. Malaccensisfrom Malaysia and Lonchocarupus utilis andD. uruca from S. America. Rotenone occurs in Derris roots (4-9%), Lonchocarpus (8-11%).

It is oxidized to non-insecticidal compound in the presence of light and air and hence rotenone residues are difficult to find after 5 to 10 days in normal sunlight. Insects poisoned with rotenone show a steady decline in oxygen consumption followed by paralysis and deaths. It is very specific being highly toxic to fishes and to most insect species but almost harmless to warm blooded animals except pigs LD50.to white rat oral-130 to 1500. Dust or spray containing 0.5 to 1.0 per cent and 0.001 to 0.002

percentrotenone are used commercially.

4) Plumbagin:

Plumbagin is naturally occurring napthoquinone of plant origin from the roots of Plumbago europea L. (Plumbaginaceae) and named so in 1828 by Bulong d’ Astafort. Plumbagin is known for its medicinal, antifertility, antimicrobial, molluscicidal, nematicidal and other pharmacological properties on diverse fauna. The yield of plumbagin ranges between 0.5-3.000percent on dry weight basis.

The elucidation of structure of plumbagin and its synthesis in 1936 led to detailed studies. More recently, its IGR properties viz., inhibition of chitin synthetase and ecdysteroid titres have been demonstrated (Kubo et al., 1982) The cold alcoholic extract (5%) of roots of P. zeylanica L was toxic to Euproctis fraterna larvae as contact spray. Contact toxicity of 5% petroleum ether extracts of P. zeylanica root against Spodoptera litura Fab., Dystercus koenigiiFab.,Dipaphis erysimi Kalt, Dactynops carthami H.R.L, Coccinella septumpunctata L was also reported.

5) Pyrethrum: It is extracted from dried flower heads of Chrysanthemum cinerariaefolium (Asteraceae). The actual chemical ingredients having insecticidal action are identified as five esters. They are: Pyrethrin I, Pyrethrin II, cinerins -I and cinerin-II and Jasmoline, which are predominately found in achenes of flowers from 0.7 to 3 %. The esters are derived from the,

Two acids – Chrysanthemic acid and Pyrethric acid

Three alcohols – Pyretholone, Cinerolone and Jasmolone

Active principles/Esters

Pyrethrin I = Pyrethrolone + Chrysanthemc acid

Pyrethrin II = Pyrethrolone + Pyrethric acid

Cinerin I = Cynerolone + Chrysanthemc acid

Cinerin II = Cynerolone + Pyrethric acid

Jasmolin II = Jasmolone + Pyrethric acid

Pyrethrum powder is prepared by grinding the flowers. The powder mixed with a diluent such as talc or clay is known as pyrethrum dust. It is prepared just before use. Otherwise it gets deteriorated rapidly. It is also used as emulsions, solutions, and aerosoles. Pyrethrum is unstable to light, air moisture and alkali. The residues deteriorate very rapidly after application. Pyrethrins are powerful contact insecticides but appear to be poor stomach poisons. A characteristic action of Pyrethroid is the rapid paralysis or ‘knock down’ effect and substantial recovery that follow it. This recovery is due to rapid enzymatic detoxification in the insect. To bring about mortality equivalent to knock down effect three times increase in dosage may be required. Compounds such as piperonyl butoxide, propyl isome and sulfoxide are known to inhibit the detoxication enzyme and increase the toxicities of pyrethroids. These synergists are used at 10 parts to 100 part of pyrethroid. LD50. for white rat oral-200 dermal for rat-1800. Pyrocon E 2/22 (1 part of pyrethrin + 10 parts of piperonyl butoxide) is used for the control of coconut red palm weevil. In household sprays and as a repellent against external parasites of livestock pyrethrum is useful. It is also mixed with grains in storage to protect from stored grain pests. Its use alone or in combination with piperonyl butoxide as food packages has been permitted by the food and Drug Administration in the U.S.A. and no other chemical has been approved.

Properties

                                                              i.      Highly unstable in light, moisture and air.

                                                            ii.      Have no residual effect.

                                                          iii.      Paralyse by more contact.

                                                          iv.      Gains entry through spiracle and cuticle.

                                                            v.      Act on central nervous system.

                                                          vi.      Having rapid knock down effect.

                                                        vii.      Practically no mammalian toxicity.

                                                      viii.      Good insecticides against household and cattle pests

Sabadilla:

• It is a alkaloid found in seeds of tropical lily Schoenocaulon officinale (fam: Liliaceae)
• The alkaloid mainly, cevadine and veratridine act as nerve poisions
• It is a primarily contact poision.
• It is harmful to pollinator, honey bees

Ryanodine:

• It is a alkaloid derived from woody stems of South American shrub, Ryania speciosa (Fam; Flacourtaceae)
• Activity: It acts as muscular poison by blocking the conversion of ADP to ATP in strated muscle.
• It acts as slow acting stomach poision and causes insects to stop feeding after they eat it.
• It is reportedly effective against thrips and worms.
• It is used as dust (20-40%)

SYNTHETIC ORGANIC INSECTICIDES

I) Chlorinated Hydrocarbons (Organochlorines): The plant protection in India owes its growth to the chemicals under this group which have revolutionized the control of pests. The properties which have lead to their extensive use are high insecticidal efficacy, long residual action, wide range of insect susceptibility, cheapness per unit area and available in different formulations.They are also known as chlorinated synthetics or chlorinated organics or chlorinated hydrocarbons. The important organochlorines are

1. DDT: DDT was first synthesized in 1874 by Othmar Zeidler. In 1939 a Swiss entomologist, Paul Muller, found its insecticidal property for the first time. This discovery brought the `Nobel Prize' for medicine to Paul Muller in 1948 for the life saving discovery. Dichloro Diphenyl Trichloroethane (DDT) is stomach and contact insecticide. It has got long residual action. It is also non-phytotoxic except to cucurbits. It is not much effective against phytophagous mites. Due to low cost of DDT and effectiveness against a variety of insects particularly against house flies and mosquitoes, it is much popularized but due to long residual life and accumulation, it is banned in several countries. The acute oral LD50 for rats is 113-118 mg/kg. It does affect the nervous system preventing normal transmission of nerve impulses. DDT causes a violent excitatory neurotoxic system in most insects which are having uncoordinated movement and DDT Jitters (tremor of the entire body).

2. Hexa Chloro Cyclohexane (HCH): It was first synthesised by Michael Faraday in the year 1825.The gamma-isomer of BHC has the insecticidal activity. BHC is a stomach and contact insecticide. It has got slight fumigant action. It is persistent insecticide. It is non-phytotoxic except cucurbits .It has been extensively used as soil insecticides particularly to control termites, white grubs and cutworms. Highly purified product containing 99% of gamma isomer of HCH is known as lindane, this name was proposed in 1949 after Vander Linden, a German chemist who isolated this isomer in 1912. Lindane is more acute neurotoxicant than DDT results in tremors, ataxia, convolutions, falling prostration and ultimately leading to death.

II) Cyclodines

Cyclodienes also act as neurotoxicants which disturb the balance of sodium and potassium ions within the neuron resulting into tremors, convulsions, prostration and ultimately the death.

The outstanding characteristic of the cyclodienes is their longer stability in the soil, resulting in more control of soil inhabiting insect pests. Some of the compound belonging to this group are chlordane (1945), aldrin and dieldrin (1948), heptachlor (1949), endrin (1951), mirex (1954), endosulfan (1956) and chlordecone 1958). Among them aldrin, chlordane and heptachlor were often in use for termite control as they are most effective, long lasting and economical insecticides but now banned by GOI.

1) Aldrin

It is persistent and non-systemic soil insecticide. It is usually recommended for the control of termites throughout India. Two German chemists Otto Paul Hermann Diels and Kurt Alder first documented the Diels-Aldernovel reaction in 1928 for which they were awarded the Nobel Prize in Chemistry in 1950 for their work Formulations: EC 30%, Granule 5% and Dusts 5%

Trade names: Octalene, Aldrex, Aldrosol, and Aldrite.

LD50 value: 67 mg/kg

2) Dieldrin

It is persistent and non-systemic insecticide used for mainly soil inhabiting insect pests. It is also not phytotoxic in recommended doses.

Formulations: Dust 2%

Trade names: Quintox, Alvit

LD50 value: 46 mg/kg

3) Heptachlor

It is a non-systemic, contact poison with fumigant action. It is effective against termites, white grubs, grass hoppers etc

Formulations: EC 20%, and Dust 5%

LD50 value: 100-162 mg/kg

4) Endosulfan:

It is a non-systemic, contact and stomach poison with slight fumigant action. It is effective against defoliators, borers, sucking insects and mites but harmless to honey bees at recommended doses for insect control. It is highly toxic to fish.

Formulations: EC 35%, Granule 4% and Dusts 4%

Trade names: Thiodan, Endocel, Endodhan, Endotaf

LD50 value: 80-110 mg/kg

III) Organophosphates

Organophosphate came to limelight during Second World War. The biological activity of these compounds was first discovered by W. Lange and Krueger in 1932. OP compounds as insecticides were mainly due to the work of Gerhard Schrader in 1937 in Germany. First OP compound TEPP (Tetra Ethyl Pyro Phosphate) followed by parathion and schradan, the first systemic insecticide. Organophosphate insecticides have two most important properties such as higher potency and low residual life. The organophosphates (OPs) inhibit the cholinesterase (Ch E) enzyme leading to blockage of synaptic  transmission of nerve impulses and finally death.

1) Malathion

It is a non systemic contact and stomach insecticideand acaricide of low mammalian toxicity. Hence it is recommended on fruits and vegetables till a few days prior to harvest. It is also recommended for storage insects and also for external application for parasites on animals.

Formulations: EC 50 and Dusts 40

Trade names: Cythion and Himala

LD50 value: 2800 mg/kg

2) Methyl parathion:

It is a contact and stomach poison with slight fumigant action. It is widely used in for sucking insects and foliage feeders.

Formulations: EC 50 and Dusts 2

Trade names: Folidal, Metacid, Paratox, Dhanumar

LD50 value: 13 mg/kg

3) Diazinon:

It is a contact persistent insecticide with nematicidal properties. It is very much useful against household insects such as flies and cockroaches.It has contact, stomach poison and also fumigant action.

Formulations: EC 20 and 5G

Trade names: Basudin

LD50 value: 300-850 mg/kg .

4) Dichlorvos (Dimethyl Dichloro Vinyl Phosphate - DDVP)

It is contact poison but due to high vapour pressure it has got strong penetrating power. It is very effective against hidden insects due to its fumigation action. It is recommended for leaf miners and leaf webbers. It brings quick knock down effect. It does not leave toxicresidues. It is highly toxic to bees. It is acontact and stomach poison with fumigant action.

Formulations: EC 76 and 5G

Trade names: nuvan, vapona, Doom, Divap

LD50 value: 56 – 108 mg/kg.

5) Fenitrothion:

It acts as contact and stomach poison with broad spectrum activity and a selective acaricide. It is effective against sucking pests including mealy bugs, borer and mites and external parasites of livestock.

Formulations: EC 35, ULV 0.05 – 0.1 and 5 Dusts

Trade names: Sumithion, Folithion

LD50 value: 50 – 250 mg/kg.

6) Quinolphos:

It is contact poison having good penetrating power and It is having acaricidal properties.It is widely used against caterpillars and borer on cotton, vegetables and other crops.

Formulations: EC 25 and 5 G

Trade names: Ekalux, Shakthi Quick, Quinguard, Quinaltaf, Smash, Flash

LD50 value: 62–137 mg/kg.

7) Phosolone:

It is a non systemic contact insecticide and acaricide, effective against wide spectrum of species.

Formulations: EC 35

Trade names: Zolone

LD50 value: 135 mg/kg

8) Chlorpyriphos:

It is a non-systemic contact insecticide very effective against sucking and chewing insects.It is also recommended against house hold insect pests. It is widely recommended as seed treatment chemical against white grub and termites.

Formulations: EC 20

Trade names: Dursban, Chloroban, Durmet, Radar

LD50 value: 135-163 mg/kg

9) Phosphomidon:

It is a systemic insecticide ha ving low contact action. It is very effective against sap sucking insect pests. On application it is absorbed in the plant tissues within 1-3 hours and is translocated more towards the top. It is less toxic to fish and more toxic to bees.

Formulations: 40 SL

Trade names: Demecron, Sumidon, Chemidan, Hydan, Phamidon

LD50 value: 17-30 mg/kg

10) Monocrotophos:

It is a systemic insecticide and acaricide with contact action. It has wide range of susceptibility of insects. It is toxic to bees.

Formulations: 36 SL

Trade names: Monocil, Nuvacron, Monophos, Monochem, Monostar

LD50 value: 14-23 mg/kg

11) Methyl demeton:

It is contact and systemic insecticide and acaricide.It is used against soft bodied insects,

which suck the plant sap.

Formulations: 25 EC

Trade names: Metasystox and Dhanusyatax

LD50 value: 57-106 mg/kg

12) Dimethoate:

It is systemic insecticide and acaricide .It is widely used against sucking insect pests on various crops.

Formulations: 30 EC

Trade names: Rogor, Celgor, Novogor, Tara 909, roxion

LD50 value: 320-380 mg/kg

13) Triazophos:

It has insecticidal, acaricidal and nematicidal properties with trnalaminar action. It is very

effective against variety of pests particularly Lepidoptera larvae on fruits and vegetables.

Formulations: 40 EC

Trade names: Hostathion, Trizocel, Truzo, Suthation

LD50 value: mg/kg

14) Profenophos:

It is a broad spectrum non-systemic insecticide.It is recommended against pest of vegetables. It is highly toxic to birds and fish.

Formulations: 50 EC

Trade names: Curacron, Celcron, Bolero, Carina, Proven

LD50 value: 358 mg/kg

15) Acephate:

It is a systemic andcontact poison.It has low toxicity and safe to environment.

Formulations: 75 SP

Trade names: Arthane, Starthane, Orthene

LD50 value: 866-945 mg/kg

16) Phorate:

It is a systemic granular insecticide and also possesses acaricidal properties. It is very effective against sucking insects and also against maize borers, cut worms, white grubs etc.

Formulations: 10 G

Trade names: Thimet

LD50 value: 1.6 – 3.7 mg/kg

CARBAMATES

All carbamates are derivatives of carbamic acid. Many of the carbamic esters are insecticidal and a few are effective molluscicides Like organophosphates, the carbamate insecticides interfere in cholinergic transmission. The carbamate enters the synapse and inhibits the acetylcholine-esterase as a result the acetylcholine contains to depolarize the post synaptic membrane, causing prolonged stimulation resulting into the failure of the nerve or effector tissue. Carbamates have an analogous action, carbamylating rather than phosphorylating the enzyme and the ChE recovers more readily from carbamates than from organophosphates. Thus, unlike, organophosphates, they are known as reversible inhibitors.

1. Carbaryl:

Carbaryl is a contact and stomach insecticide. It is most popular insecticide because it is effective against a wide range of insects and possesses very low mammalian toxicity. It is compatible with many pesticides except Bordeaux mixture lime sulphur and urea. It is not effective against mites.

Formulations: WP 50%, Granule 4% and Dusts 5%

Trade names: Sevin.

LD50 value: 400 mg/kg

2. Propoxur(Arprocarb)

It is a broad spectrum, contact and stomach poison with good knock down properties. It is effective in controlling house hold pests such as cockroaches, crickets, flies etc. It has long residual action.

Formulations: 20% EC, 50% WP

Trade names: Baygon, Bla ttamen, Saphaer

LD50 value: 90-128 mg/kg

3. Carbofuran.

It is a plant systemic broad spectrum and long residual insecticide, miticide and nematicide. It is recommended as soil insecticides against plant sap sucking and borer

pests.

Formulation: 3G,48F

Trade names: Furadan

LD50 value: 8-14 mg/kg

4. Carbosulfan.

It is a systemic insecticide, and nematicide. It is recommended as seed dresser insecticide

Formulation: 25 DS

Trade name: Marshal

5. Thiodicarb

It is a insecticide with ovicidal properties, and molluscicide.

Formulation: 75 WP

Trade name: Larvin

6. Aldicarb

It is systemic pesticide usually applied in soil as seed furrow, band or broadcast treatments either pre-plant or at planting as well as post emergence side dress treatments. It has also possessing acaricidal property and toxic to higher animals. Insecticide of carbamate group which is highly toxic to mammals.

Formulation: 10 G

Trade names: Temik

LD50 value: 0.93 mg/kg

5. Methomyl:

It is a systemic with contact and stomach insecticide and nematicide. It is very effective against a wide variety of pests particularly army worms, cabbage semilooper, Okra stem fly, fruit borers, leaf defoliators, cotton boll worms, etc. It is insecticide belonging to carbamate groups that has ovicidal action against lepidopteran pests (Helicoverpa armigera).

Formulations: 90 WP,12.5 EC, 40 SP

Trade names: Lannate, Dunnate

LD50 value: 30 mg/kg

SYNTHETIC PYRETHROIDS AND INSECTICIDES OF OTHER GROUPS

Synthetic pyrethroids have got the properties of plant derivative pyrethrum as insecticides but areconsiderably more stable in light and air. Allethrin was first synthetic analogue of pyrethroids.

They act on tiny channel through which sodium is pumped to cause excitation of neurons and prevent the sodium channels from closing,resulting in continual nerve trans mission, tremors and eventually death.

The synthetic pyrethroids have extremely high insecticidal activity at extremely low doses and are bio-degradable in nature. Their activity is most pronounced against lepidopterous pests and they are very effective against beetle, leaf miner and bugs. They are very effective against eggs, larval and adult stages of insects. They have antifeedant and repellent properties. They are not readily washed off from the plants by rain due to lipophilic characters.

These synthetic pyrethroids are very less toxic to mammals and having a quick knock down activity to insects, the lower toxicity to mammals and increase safety for  the user.Very low application rate of synthetic pyrethroids as compared to conventional  insecticides brings reduced environmental pollution.

Limitations

1. A major limitation of synthetic pyrethroids is that these are generally not effective as soil insecticide.
2. Even at low dosages kill non target species.
3. Synthetic pyrethroids cause resurgence of several groups of insect pests especially whiteflies and aphids.
4. Rapid development of resistance to synthetic pyrethroids in many insect species. This may be due to high selection pressure exerted by high mortality caused by synthetic pyrethroids
5. Synthetic pyrethroids are poor acaricides

First generation: First generation pyrethroids are considered to be of low toxicity to people and other mammals because they are rapidly broken down in the body. First generation pyrethroids decompose quickly in sunlight and air and thus pose little risk in the environment but all pyrethroids are toxic to aquatic animals.

1) Allethrin

It is contact, stomach and respiratory action and bring quick knock down of flies and mosquitoes when applied in combina tion with Piperonyl butoxide. These are lipophlic compounds. In 1949, the first synthetic pyrethrum analougue allethrin commercially introduced.

Trade name: Pynamin

LD50 value: rats 572-1100 mg/Kg for rats and Dermal LD50 >2000 mg/kg

Second generation: Second generation pyrethroids are not acutely toxic to people or other mammals.These pyrethroids decompose rapidly in sunlight. They thus pose little threat to the environment, but for the same reason they are not suitable for agricultural use.

2) Resmethrin

. Approximately 20 times more effective than pyrethrum in housefly knock down, and is not synergized to any appreciable extent with pyrethrum synergists.

Trade name: NRDC – 104, SBP-1382, and FMC – 17370

LD50 value Dermal LD50 2000-3000 mg/kg

3) Bioresmethrin

It is stereoisomer of resmethrin. Appeared in 1967.50 times more effective than pyrethrum against normal (susceptible to insects) houseflies, and also not synergized with pyrethrum synergists. Both resmethrin & Bioresmethrin decompose fairly rapidly on exposure to air & sunlight, so never developed for agricultural use.

Trade name: NRDC-107,FMC –18739, and RU-1148

LD50: 8,600 mg/kg (oral) and 10,000 mg/kg (dermal).

4) Bioallethrin (d-trans –allethrin) introduced in 1969. More potent than

allethrin and readily synergized, but it is not as effective as resmethrin.

Third generation: Third generation pyrethroids do not decompose in sunlight and contain some of the most powerful insecticides known. Third generation pyrethoids are not highly toxic to people or other mammals mainly because they decompose rapidly in the body.

5) Fenvalerate:

It is contact insecticide and of broad spectrum in nature. It is stable in sunlight and has longer residual toxicity.

Formulations: 20 EC

Trade names: Fenvel, Bilfen, Belmark, Sumicidin, Pydrin

LD50 value: 300-630 mg/kg

6) Permethrin:

Contact insecticide, light stable, but poor knock down. First agricultural pyrethroidsbecause of their exceptional insecticidal activity (0.11 kg a.i/ha) and their photo stability.

Formulations: 25 EC and 5% smoke generation

Trade names: Ambush , pounce , pramex

LD50 value: Acute oral LD50 : 7000 mg/kg, Dermal LD50: >5100 mg/kg

119

Fourth generation: Offer the most resistance to exposure to sunlight and air and, therefore, are more persistent. This group is more toxic to people than other pyrethroids and therefore requires more care in use. More stable in the environment.

7)  Cyhalothrin

Non-systemic insecticide with contact and stomach action, and repellent properties.gives rapid knockdown and long residual activity. It is an insecticide and acaricide used to  control a wide range of pests.

Formulations: 2.5 EC, 5% EC

Trade names: Kung-Fu,Reeva, Charge, Excaliber, Grenade, Hallmark, Karate,

Matador, Samurai and Sentinel.

LD50 value: 56 mg/kg

8) Cyfluthrin

It is a non-systemic contact and stomach poison,with rapid knock down effect. It is for control of chewing and sucking insects on crops. Cyfluthrin is also used in public health situations and for structural pest control.

Formulations: 5 EC, 10% EC

Trade names: Contur, Laser, Responsar, Tempo

LD50 value: 869 - 1271 mg/kg

9) Cypermethrin

It is stomach and contact insecticide. It is very effective against different types of pests on various crops.

Formulations: 10 EC, 25 EC

Trade names: Cyper guard, Ripcord, Cymbush and Cyper kill

LD50 value: ha Oral LD50 303-4123 MG /KG, dermal more than 2400mg/kg

10) Fenpropathrin

It is contact insecticide and of broad spectrum in nature.It is extremely toxic to fish, wildlife.and aquatic organisms. It have acaricidal and miticidal property.

Formulations: 2.4 EC, 10 or 20% EC.

Trade names: Danitol, Rody and Meothrin

LD50 value:54 mg/kg

11) Flucythrinate

Flucythrinate is a synthetic pyrethroid used to control insect pests in apples, cabbage, field corn, head lettuce and pears, and to control Heliothis spp. in cotton.

Trade names: AASTAR, AC 222705, Cybolt, Fuching Jujr, OMS 2007, and Pay-Off.

LD50 value: 81 mg/kg .dermal LD50 in rabbits of greater than 1000 mg/kg

12) Decamethrin (Deltamethrin)

It is more potent than any other insecticide. It has also proved effective even against insects resistant to conventional insecticides.It is contact and stomach insecticide.

Formulations: 2.8 EC, 2.5% WP

Trade names: Decis, Decaguard, Deltex

LD50 value:135mg/kg

13) Fluvalinate

It is a insecticide and acaricide with stomach and contact activity in target insects. It

is used as a broad spectrum insecticide.

Formulations: 25 EC

Trade names: Klartan, Mavrik, Mavrik Aqua Flow, Spur and Yardex

LD50 value: 1,050 to 1,110 mg/kg

14) Fenfluthrin: It is a very potent recent synthetic pyrethroid against a various groups of insects and mites. Highly toxic to Daphnia (Aquatic Invertebrate)

Trade Names: Bayticol, Bayvarol, Baynac