Here is a list of chemicals that will help you to control pests: 1. Insecticides 2. Acaricides 3. Nematicides 4. Rodenticides 5. Molluscicides.
1. Insecticides:
I. Chlorinated Hydrocarbons:
(i) DDT (Dichlorodiphenyltrichloroethane):
DDT (C14H9Cl5) (Fig. 7.1) was introduced in 1942 by J.R. Geigy under the trade names Gesarol, Guesarol and Neocid. Its insecticidal properties were, however, discovered by Paul Muller in 1939. It is a potent non-systemic stomach and contact insecticide, effective against a wide range of insects, including pests of crops and household goods. It is also of importance in public health. It has no action on phytophagous mites and, when used on crops against insects, the mite population increases invariably. DDT is generally non-phytotoxic, but it damages cucurbits.
At low concentrations, it stimulates the plant growth in crops like potato, tomato, cabbage and brinjal. Because of its wide spectrum effectiveness it is not safe to most natural enemies of insect pests. Its acute oral LD50 for male rat is 113 mg/kg, for female rats 118 mg/kg; the acute dermal LD50 for female rats is 2,510 mg/kg. In India it is being manufactured by M/s Hindustan Insecticides Limited.
DDT is sold under the trade names of Chlorophe-nothene, Guesarol, Teffidex, etc., and is available in various formulations including EC, WP and dust. It is applied at the rate of 0.50-2.50 kg per ha in concentrations varying from 0.1-0.25 per cent on practically all crops except the cucurbits. It is effective against jassids, white flies, bollworms, pyrilla, leafminers, capsule and pod borers, beetles, but should not be used on farm animals or inside the houses.
It persists for quite a long time on the plants, in the soil, and it also accumulates in the body fat of birds, fishes and mammals. It is then secreted in the milk. Owing to its repeated use, even though some of the insects have developed resistance, it still continues to be a leading protective insecticide for outdoor use. The use of DDT in agriculture has recently been banned in India.
(ii) Methoxychlor [1, 1, 1-Trichloro-2, 2, di-(3 Metho-Xyphenyl Ethane)]:
The insecticidal properties of methoxychlor (Fig. 7.1) were first discovered in 1944 and it was introduced in 1945 under the trade name ‘Marlate’. It is also known as dimethoxy-DT, DMDT, dianisyl trichloroethane. It is a non-systemic, contact and stomach insecticide but has little aphicidal and acaricidal activity. Its range of activity is as wide as that of DDT but unlike DDT, it shows little tendency to be stored in body fat. It is, therefore, used for fly control in dairy barns. It is available as a WP of different strengths and also as EC.
(iii) Toxaphene:
Toxaphene (approximately C10H10Cl8) was first described by W. Le Roy Parker and J.R. Beacher in 1947 but was introduced in 1948 by Hercules Incorporated under the code number ‘Hercules 3956’. It is a non-systemic and persistent contact and stomach chlorinated terpene with some acaricidial action. It is non-phytotoxic except to cucurbits. However, it is harmless to bees. The acute oral LD50 for male rats is 90 mg/kg, for female rats 80 mg/kg; the acute dermal LD50 for male rats is 1,075 mg/kg, for female rats 780 mg/kg.
Toxaphene has had by far the greatest use of any single insecticide in agriculture. It is a mixture of more than 177 polychlorinated derivatives, which are 10-carbon compounds including Cl6, CI7, Cl8, Cl9 and Cl10 constituents. No single component makes up more than a small percentage of the technical mixture. Toxaphene is manufactured by the chlorination of camphene, a pine tree derivative.
These materials are persistent in the soil, though not long lasting as other cyclodienes. It disappears in three to four weeks from the surface of most plant tissues. The modes of action of toxaphene and strobane are similar to other cyclodiene insecticides by acting on the neurons and by causing an imbalance in sodium and potassium ions.
Toxaphene is also sold under the trade name of Anatox, and is available in formulations of EC and dust. It is applied at the rate of 2.0 kg per ha or 0.1 to 0.2 per cent concentration against hairy caterpillars and armyworms, feeding on weeds and field crops. It is also effective against termites and cutworms.
(iv) BHC (Benzene Hexachloride):
The insecticidal properties of ‘gamma’ isomer of BHC (misnomer for HCH) (Fig. 7.1) were discovered in the early 1940s and the compound was introduced by the Imperial Chemical Industries under the trade name ‘Gammexane.’ HCH is a persistent stomach poison and a contact insecticide with some fumigant action also.
It is a mixture of several isomers of which gamma is the most toxic to insects and is the main (13 %) insecticidal component of HCH. It is non- phytotoxic, except to cucurbits, at the normal insecticidal concentrations, but at higher concentrations it may cause root deformation and polyploidy. It taints certain foods, such as potatoes. Pure gamma HCH commonly known as lindane, was introduced to overcome the tainting effects.
It is quite persistent on the plants and accumulates in the soil and in the animal system. Both HCH and lindane are formulated as dust, WP, granules, EC and smoke. The use of HCH on vegetables, fruits, oilseed crops and preservation of food-grains in India had been banned earlier. Now, there is a total ban on manufacture and use of HCH in India with effect from 1st April, 1997.
(v) Chlordane:
Octachloro-4, 7 methano-tetra-hydroindane (C10H6Cl8) (Fig. 7.1) was introduced as an insecticide in 1945 by Velsicol Chemical Co. under the name of Chlordane. It is a contact and stomach poison and also shows fumigant properties with long residual effects. It is a non-systemic and non- phytotoxic insecticide with LD50 value of 335 mg/kg.
Chlordane is sold under the trade names of Octachlor, Intox, Chlordan, etc. as EC, WP and dust. It is applied at the rate of 1.0-4.0 kg ha. It gives termite control upto five years. It has also been used against grasshoppers, Japanese beetles, field crickets, spiders and mosquitoes.
(vi) Heptachlor:
Heptaclorotetrahydro-4, 7-metha-noindane (C10H7CI7) (Fig. 7.1) was introduced as Heptachlor by Velsicol Chemical Co. in 1945. It is a contact and stomach poison with long residual effects. It is a non-systemic and non-phytotoxic insecticide with LD50 value of 100 mg/kg.
It is also sold under the trade names of Heptagran and Drinox as EC, WP, dust and granules. It is applied at the rates of 1.0-4.0 kg a.i. per ha. It has been recommended for use against termites, Japanese beetle, grasshoppers, mosquitoes, etc. It has been used to protect the turfs from the damage of white grubs.
(vii) Aldrin and Dieldrin:
Aldrin (C12H8Cl6) (Fig. 7.1) was introduced in 1948 by J. Hyman & Co. as ‘Compound 118’ under the trade name of Octalene and its insecticidal action was first described by Kearns and co-workers in 1949. It is a non-systemic and persistent contact cyclodiene insecticide. It is usually non-phytotoxic. The acute oral and dermal LD50 values for rat are 40-50 and 100 mg/kg, respectively. It is manufactured in India by M/s National Organic Chemicals Industries Ltd.
Aldrin is sold under the trade names of HHDN, Octalene and Aldrex, and is available as EC and dust. It is basically a soil insecticide and is applied at the rate of 1.75 kg a.i. per ha in concentrations varying from 0.02 to 0.2 per cent. Its soil application is recommended in fields of wheat, sugarcane and cotton. It is effective against termites, black ants, hairy caterpillars, root weevils and other soil dwelling pests. The use of aldrin has recently been banned in India.
Dieldrin (Fig. 7.1) was introduced as an insecticide in 1949. It is a non-systemic and persistent insecticide with high contact and stomach action. It is also non-phytotoxic. This insecticide is highly stable and compares well with most other pesticides. Like aldrin it also has a high dermal toxicity and should be used with care. It is available as an emulsifiable concentrate.
(viii) Endrin:
Hexachloroepoxyoctahydro-endo, endo-dimethanonaphthalene (C12H8Cl6O) was introduced as an insecticide by Shell Chemical Co. in 1950 as Endrin. It is an isomer of dieldrin. It is a contact and stomach poison. Usually it is non-phytotoxic except on corn and cucumber. It is a non-systemic insecticide with LD50 value as low as 10 mg/kg for mammals. It is highly toxic to fish and is also absorbed, through skin.
It is marketed as EC, WP, dust and granules. It is effective against a wide range of sucking and biting insects and has very long residual effect. Because of its high mammalian toxicity and long residual effects, its use has now been banned in many countries of the world, including India.
(ix) Endosulfan:
The insecticidal properties of endosulfan (C9H6Cl6O3S) (Fig. 7.1) were first described by W. Finkenbrink in 1956 and it was introduced in 1956, by Farbwerke, Hoechst A.G. under the trade name Thiodan. It is a non-systemic contact and stomach insecticide. It is highly toxic to fish but, in practical use, is comparatively safer to wildlife and bees. Its acute oral and dermal LD50 values for rat are 43 and 130 mg/kg, respectively. Both M/s Hoechst Pharmaceuticals Ltd. and M/s Excel Industries Limited manufacture endosulfan in India.
Endosulfan is sold under the trade names of Thiodan, Hexasulfan and Thionex, and is available in various formulations including EC, dust and granules. It is applied at the rate of 225-875 g a.i. per ha in concentrations ranging from 0.02 to 0.1 per cent on cotton, redgram, wheat, rapeseed and mustard, brinjal, cabbage, tomato, okra, peas, sugarcane and mango.
It is effective against tissue borers, stemfly, bark-eating caterpillars, semiloopers, armyworms, cutworms, leaf-rollers, hairy caterpillars, bugs, chaffer beetles, leafhoppers, pyrilla, aphids, thrips, white flies and gall midges. On May 13, 2011, the Supreme Court of India had banned the manufacture, sale and use of endosulfan in the country.
II. Organophosphates:
(i) Parathion and Parathion-methyl:
Ethyl parathion, commonly known as parathion, was the first organophosphorus insecticide introduced in 1948 under the trade name of Folidol. It is a potent contact and stomach insecticide with some fumigant action but is non-systemic. It is highly effective against scale insects, aphids and mites, and its residues do not persist for long. It is non-phytotoxic, except to certain ornamentals and fruit plants.
As its dermal toxicity is very high, it is highly toxic to mammals, although it is non-cumulative. It should not be used in houses or on livestock. Its use should also be avoided on crops in blossom, firstly because the flowers are damaged and secondly because the bees and other pollinators are killed. It is available as a WP, EC, dust, smoke and aerosol.
Parathion-methyl (C8H10NO5PS) (Fig. 7.2) was first described by G. Schrader and was introduced in 1949 by Farbenfabriken Bayer A.G. under the trade names of Dalf, Folidol-M, Metacid, Nitrox 80, the latter two being registered by Chemagro Corporation.
Parathion-methyl is a non-systemic contact and stomach phosphorothionate insecticide with some fumigant action. It is non-phytotoxic. It is hazardous to wildlife but is of short persistence. The acute oral LD50 for male rats is 14 mg/ kg, for female rats 24 mg/kg; the acute dermal LD50 for rats is 67 mg/kg. M/s Bayer (India) Ltd. manufactures these insecticides in India.
Parathion-methyl (O, O-dimethyl O-p-nitrophenyl phosphorothioate) is an organophosphoro-thioate phenyl derivative. It became available in 1949 and proved to be more useful than ethyl parathion because of its lower toxicity to humans and domestic animals, and with broader range of insects that it controlled. Its shorter residual life also makes it more desirable in certain situations.
Parathion-methyl is sold under the trade names of Metron, Nitrox, Metacid and is available in the form of EC. It is applied at the rate of 500 g a.i per ha in 0.05 per cent concentration on a number of field crops except those eaten as green vegetables. It is effective against tissue borers, scale insects, armyworms, hispa, coccids and mealy bugs.
(ii) Malathion:
Malathion (C10H19O6PS2) (Fig. 7.2) was introduced in 1950, by the American Cyanamid Company under the code number ‘Experimental Insecticide 4049’. It is a non-systemic contact phosphorothiolothionate insecticide and acaricide of low mammalian toxicity with short to moderate persistence.
It is generally non-phytotoxic but may damage cucumber, spring bean and squash under glasshouse conditions. It is highly toxic to bees. The acute oral LD50 for rat is 1,375 mg/kg; the acute dermal LD50 for rabbit is 4,400 mg/kg. M/s Excel Industries Limited manufactures malathion in India.
Malathion is sold under the trade names of Cythion, Malamar, Malathion and is available in various formulations including EC, LVC, dust, etc. It is applied at the rate of 0.5-2.5 kg a.i. per ha in concentrations varying from 0.05-0.15 per cent on a number of crops particularly those which are edible in green or ripe stage of growth. It is effective against tissue borers, caterpillars, bugs, leafhoppers, aphids, thrips, whiteflies, mites, fruit-flies, grasshoppers, midges, pests of household and farm animals.
(iii) Schradan (OMPA):
It is one of the first systemic compounds whose insecticidal properties were discovered in 1941. It is effective against sap-sucking insects and mites, but has little effect as a contact poison. It is non-phytotoxic at insecticidal concentrations, but its mammalian toxicity is rather high. Its use on edible crops is also restricted. It is a selective insecticide and is less destructive to parasites, predators and insect pollinators. Schradan is formulated as an aqueous solution.
(iv) TEPP (Tetra-Ethyl Pyrophosphate):
The aphicidal properties of this compound were discovered in 1938. In 1943, a derivative of hexaethyl tetraphosphate (HETP) was introduced and was shown to contain TEPP as the main active compound. TEPP was introduced as a substitute for nicotine sulphate in Germany during the Second World War.
Due to its high mammalian toxicity it should be handled carefully. It is also hazardous to insect pollinators. In the commercial products, the mixture of polyphosphate contains 40 per cent of pyrophosphate and is marketed either in a non-water solvent solution or for use as an aerosol.
(v) Diazinon:
Diazinon (C12H21N2O3PS) (Fig. 7.2) was introduced in 1952 by J.R. Geigy, S.A. under the code number G-24480 and trade name of Basudin. It is non-systemic phosphorothionate insecticide with some acaricidal action. It is a contact and stomach poison, and has a fumigant effect.
It is non-phytotoxic but highly toxic to bees. The acute oral LD50 for male rats is 108 mg/kg, for female rats 76 mg/kg, for mice 82 mg/kg; the acute dermal LI50 for male rats is 900 mg/kg, for female rats 455 mg/kg. It is manufactured in India by M/s Rallis (India) Ltd.
Diazinon is sold under the trade names of Basudin, Spectracide, Tik- 20, Ditaf, Diazol and is available as EC and granules. It is applied at the rate of 125-1000 g a.i. per ha in concentrations ranging from 0.025-0.1 per cent on a number of field crops, fruits and vegetables. It is particularly effective against root weevils, diamondback moth, mealy bugs, rice borers and the allied tissue borers.
(vi) Trichlorphon:
Tricolorphon (C4H8Cl3O4P) was introduced in 1952, by Farbenfabriken Bayer AG under the code number Bayer L 13/59, and trade names of Dipterex, Neguvon and Tugon. It is a contact and stomach phosphonate insecticide with some fumigant action. It is non-phytotoxic but is toxic to bees. The acute oral LD50 for male rats is 630 mg/kg, for female rats 560 mg/kg; the acute dermal LD50 for rats is more than 2,000 mg/kg. M/s Bayer (India) Ltd. manufactures this insecticide in India.
Trichlorphon is sold under the trade names of Dipterex, Dylox, Neguvon, Tugon, Chlorophos and Danex, and is available in various formulations including EC, WP and dust. It is applied at the rate of 0.25-1.25 kg a.i. per ha in concentrations varying from 0.075-0.1 per cent on a number of crops and as a dip against the external parasites of farm animals. It is effective against tissue borers, army worms, hairy caterpillars, diamondback moth, leaf miners, aphids, leafhoppers and fruit flies.
(vii) Mevinphos:
Mevinphos (C7H13O6P) was introduced as an insecticide by Shell Chemical Co. in 1953 under the trade name of Phosdrin. It is a contact insecticide with acaricidal activity. The LD50 is 6.1 mg/kg.
It is available as emulsifiable concentrate and a water soluble preparation. It is non-phytotoxic with very low persistence in the soil. It is used at the rate of 0.25-1.25 kg a.i. per ha. It is recommended for use against aphids, caterpillars, leaf-miners, grasshoppers, mites, etc.
(viii) Azinphos Methyl:
Azinphos methyl (C10H14O3 N3PS) was introduced by Farbenfabriken Bayer A.G., Germany in 1954 under the trade name of Guthion. It is a contact poison with long residual activity. LD50 is 13 mg/kg. It has acaricidal properties also. It is a non-phytotoxic insecticide.
It is also sold under the trade names of Gusathion and DBB, as EC, WP, dust and granules. It is applied at the rate of 1.0 – 2.5 kg a.i. per ha. It is used against aphids, mites, caterpillars, grasshoppers, etc. It is prohibited from use on greenhouse insect pests.
(ix) Acephate:
Acephate (C4H10NO3P5) is a systemic insecticide with moderate persistence (10- 15 days) and is effective against lepidopterous larvae, sucking pests, etc. It is formulated as 75% SP. The acute oral LD50 for rat is 886-945 mg/kg and dermal LD50 for rabit is 2000.
(x) Thiometon:
Thiometon (C6H15O2PS8) was introduced by Sandoz Limited in 1953 under the trade name of Ekatin. It is a contact as well as systemic insecticide-acaricide and is usually non- phytotoxic. The LD50 is 100 mg/kg and it is absorbed through skin.
It is marketed as EC and dust. It is applied at the rate of 0.1 per cent as spray. It is reported to be effective against aphids, mites, sawflies, psyllids, thrips, etc., and is applied on ornamental plants also. It persists for 2-3 weeks on plants.
(xi) Phorate:
Phorate (C7H17O2PS3) (Fig. 7.2) was introduced in 1954, by the American Cyanamid Company under the code number ‘Experimental Insecticide 3911’ and the trade name of Thimet. It is a systemic phosphorothiolo-thionate insecticide with little contact and fumigant action. It has also nematicidal and acaricidal action. The acute oral LD50 for male rats is 2.3 mg/kg, for female rats 1.6 mg/kg; the acute dermal LD50 for male rats is 6.2 mg/kg, for female rats 2.5 mg/kg. M/s Bayer (India) Ltd. manufactures it in India.
Phorate is sold under the trade name of Thimet, as granules which have a concentration of 10 per cent of insecticide. In terms of actual ingredient it is applied at the rate of 0.75-3.0 kg per ha. It is mixed in the soil near the plant root zone and is also applied topically at strategic spots in a number of crops. It is effective against root weevils, tissue borers, maggots, leafhoppers, aphids, white flies and it acts both as a contact insecticide and as a stomach poison.
(xii) Oxydemeton-methyl:
Oxydemeton-methyl (C6H15O4PS4) was introduced in 1960, after tests since 1956, by Farbenfabriken Bayer A.G. under the code numbers Bayer 21097 and R 2170. It is a systemic and contact phosphorothiolate insecticide with acaricidal properties also.
It is non- phytotoxic and safe to parasitoids and predators but toxic to bees. The acute oral LD50 for male rats is 65 mg/kg, LD50 for female rats is 75 mg/kg, and the acute intraperitoneal LD50 for male rats is 250 mg/ kg. M/s Bayer (India) Ltd. manufactures it in India.
Oxydemeton-methyl is sold under the trade names of Metasytox, Methyl-O-demeton, and is available in the form of EC. It is applied at the rate of 125-250 g a.i. per ha in concentrations ranging from 0.025-0.05 per cent in various field crops except those, eaten as green vegetables. It is very effective against leafhoppers, aphids, white flies, thrips, leaf-miners and tingid bugs.
(xiii) Carbofenothion:
Carbofenothion (C11H16O2PS3) was introduced in 1955 by Stanffer Chemical Co. under the trade names of Trithion and Garrathion. It is non-systemic acaricide and insecticide having a long residual action. It is used on deciduous fruits, in combination with petroleum oil as dormant spray for the control of scale insects, mites and aphids. It is less toxic to honeybees than DDT and to natural enemies (parasites) than parathion. It is formulated as dust, WP and EC.
(xiv) Dichlorvos (DDVP):
Insecticidal properties of dichlorvos (C4H7Cl2O2P) (Fig. 7.2) were first described in 1951, by Ciba AG in BP 775,085 but it was given an incorrect structure in the patent. It was later introduced by Ciba AG under the trade names of Nogos and Nuvan. It is a contact and stomach insecticide with fumigant and penetrant action because of its high vapour pressure.
It is non-phytotoxic, moderately toxic to fish but highly toxic to bees. The acute oral LD50 for albino male rats is 80 mg/kg, for female rats 56 mg/kg; the acute dermal LD50 for albino male rats is 107 mg/ kg, for female rats 75 mg/kg. M/s Bayer (India) Ltd. manufactures it in India.
Dichlorvos is sold under the trade names of DDVP, Vapona, Nuvan, Nogos, Dentavepon, Marvex and Divipan, and is available in the form of EC. It is applied at the rate of 200-500 g a.i. per ha in concentrations varying from 0.03-0.1 per cent on a variety of crops ranging from evergreens to deciduous trees. It is effective against hairy caterpillars, armyworms, tissue borers, tingid bugs, white flies, woolly apple aphid, etc.
(xv) Dimethoate:
Dimethoate (C5H12NO3PS) (Fig. 7.2) was first described by Hoegberg and Cassaday in 1951 and was introduced in 1956 by the American Cyanamid Company under the code number ‘Experimental Insecticide 12,880’. It is a systemic and contact phosphorothiolo-thionate insecticide and acaricide.
It is phytotoxic to certain varieties of sorghum, hops, olives, figs, chrysanthemum, begonia, jacobinas and sunnhemp. The acute oral LD50 of the pure compound for rats is 250-265 mg/kg, for mice 285 mg/kg; the acute oral LD50 of the technical product for mice is 155 mg/kg. It has a low mammalian dermal toxicity of 610 mg/kg. M/s Rallis (India) Ltd. manufacture it in India.
Dimethoate is sold under the trade names of Rogor, Dimethoate, Perfekthion, Roxion and Cygon as EC. It is applied at the rate of 375-750 g a.i. per ha in concentrations ranging from 0.03-0.1 per cent in practically all the field crops including fruit trees. It is effective against tissue borers, leaf feeding caterpillars, leafhoppers, aphids, thrips, psylla, mites, white flies, mealy bugs and tingid bugs.
(xvi) Phosphamidon:
Phosphamidon (C10H19CINO5P) (Fig. 7.2) was introduced in 1956 by Ciba AG under the code number Ciba 570. It is a systemic and contact phosphate. Phosphamidon is less toxic to fishes but toxic to bees. It is non-phytotoxic except to certain cherry varieties. The insecticidal activity of the beta-isomer is several times greater than that of the alpha-isomer. The acute oral LD50 for rats is 23.5 mg/kg; the acute dermal LD50 for rats is 143 mg/kg. M/s Ciba Geigy (India) Ltd. manufactures this insecticide in India.
Phosphamidon is sold under the trade name of Dimecron and is available in the form of WSC. It is applied at the rate of 165 g a.i. per ha in concentrations ranging from 0.02-0.5 per cent on most of the field crops. It is effective against tissue borers, caterpillars, bugs, leafhoppers, aphids, white flies and mites.
(xvii) Menazon:
Menazon (C5H12N5O2PS2) was introduced by Plant Protection Ltd., England, under the trade name of Sayfos. It is a selective, systemic insecticide-cum-acaricide. It is reported to be phytotoxic to cruciferous vegetables. It has low mammalian toxicity and LD50 for rats is reported to be 1200 mg/kg.
It is sold under the trade names of Sayfos, Saphicol, Saphizon and Saphos. It is available as EC and WP. It is applied at the rate of 0.50-1.25 kg a.i. per ha. Tuber and seed treatments are made at 0.5 per cent concentrations by weight. In the field, it is recommended for use on apples, potato, sugarbeet, tobacco, peas, etc. against aphids, mites, leafhoppers, etc. It is most effective as an aphicide.
(xviii) Formothion:
Formothion (C6H12O4PS2) was introduced by Sandoz Ltd. in 1962 as Anthio. It is a contact as well as systemic insecticide-cum-acaricide. It is usually non-phytotoxic except on chrysanthemum and hops. The dermal toxicity to mammals at LD50 is 310 mg/kg.
It is also sold under the trade name of Aflix and is colourless and odourless. It is available as EC and is applied at the rate of 175 g a.i. per ha or at a concentration of 0.05 per cent on green vegetables, tea, coffee and ornamental plants. It is recommended for use against mites, aphids, psyllids, leafhoppers, thrips, etc. It is toxic to bees and fish.
(xix) Phenthoate:
Phenthoate (C12H18O4PS2) is a wide spectrum contact organo-phosphatic insecticide and acaricide. It is phyto toxic on some vines, peach and apple varieties. Its acute oral and dermal LD50 to rats are 200-300 and 700-1400 mg/kg, respectively. In India, M/s Bharat Pulverising Mills (P) Ltd., Mumbai and M/s Motilal Pesticides (India) Pvt. Ltd., New Delhi manufactures and formulates this product.
Phenthoate is sold under the trade names of Elsan, Cidial and Phendal, and is available in the form of EC. It is applied at the rate of 500 g a.i. per ha, generally at the concentration of 0.05 per cent, on a number of crops. It is effective against the bollworm complex, tissue borers and leafhoppers.
(xx) Fenitrothion:
Fenitrothion (C9H12P5NPS) (Fig. 7.2) is a low toxic organophosphorus contact insecticide discovered in 1959 by the research group of Sumitomo Chemical Co. Ltd., Osaka, Japan. It is toxic to bees. It is also selective acaricide but of low ovicidal activity. Phytotoxicity may be caused on Brassica crops, certain susceptible apple varieties and cotton when applied at high dosages. It’s acute oral and dermal LD50 for rats are 250-673 and 1500-3000 mg/kg, respectively. M/s Cyanamid India Ltd., Mumbai; M/s Bayer (India) Limited, New Delhi and M/s Rallis India Limited, Bangalore, are the manufacturers of fenitrothion in India.
Fenitrothion is sold under the trade names of Sumithion, Folithion, Accothion, Bayer 41-831 and Hexafin, and is available in the form of EC, WP and dust. It is applied at the rate of 0.5-1.0 kg a.i. per ha in varying concentrations at 0.025-0.05 per cent on a number of crops except those which are tall or those which are used as green food or fodder. It is highly effective against the white grub adults, armyworms, thrips, aphids, tissue borers, bollworms, tingid bugs, weevils, white flies, webworms, leafhoppers and leaf-feeding caterpillars.
(xxi) Ethion:
Ethion (C9H22O4P2S4) is a non-systemic insecticide effective against aphids, scales and thrips, and an acaricide. It can be used on tea and in combination with petroleum oils on dormant fruit trees for the control of scales and as an ovicide. It is available in the form of 50% EC. The oral LD50 for rat is 65 mg/kg, whereas the dermal LD50 for rabbit is 245 mg/kg.
(xxii) Monocrotophos:
Monocrotophos (C7H14NO5P) (Fig. 7.2) is a contact and systemic organo-phosphorus insecticide. It was introduced in 1965 by Ciba A.G. under the code number C 1414 and trade name of Nuvacron and by the Shell Development Co., under the trade name of Azodrin. On certain varieties of cherry and some varieties of sorghum it causes scorching of the edges of the leaves.
The formulations corrode iron, tin, plate and aluminium. The acute oral LD50 for rats is 21 mg/kg; the acute dermal LD50 for rabbits is 354 mg/kg. It is toxic to bees. M/s Ciba-Geigy India, Mumbai and M/s NOCIL India, New Delhi, manufacture monocrotophos in India.
Monocrotophos is sold under the trade names of Azodrin, Nuvacron, Monocron and Monocil, and is available in the form of EC. It is applied at the rate of 0.50-1.25 kg a.i. per ha in concentrations varying from 0.03 to 0.1 per cent on a large number of crops. It is effective against the bollworm complex of cotton, tissue borers, tingid bugs, aphids, thrips, whiteflies, leaf-miners, planthoppers, hairy caterpillars, mealy bugs, whorl maggots and leafhoppers.
(xxiii) Quinalphos:
Quinalphos (C12H15O3H2PS) (Fig. 7.2) is a contact and stomach organophos- phorus insecticide and acaricide. It was introduced by Bayer in 1969 under the code No. Bayer 77049. Its acute oral LD50 and acute dermal LD50 for rats are 62-137 and 1250-1400 mg/kg, respectively. In India, M/s Sandoz (India) Ltd., Mumbai, manufacture quinalphos.
Quinalphos is sold under the trade names of Ekalux, Bayrusil, Sandoz 6538 and Bayer 77049 and is available in various formulations including EC, granules and dust. It is applied at the rate of 125-500 g a.i. per ha in concentrations varying from 0.025 to 0.2 per cent on a large number of crops. It is effective against the bollworm complex, armyworms, diamondback moth, hairy caterpillars, tissue borers, thrips, leaf miners, web-worms, mealy bugs, hadda beetles, etc.
(xxiv) Phosalone:
Phosalone (C12H15 CINO4PS2) was discovered in 1960. It is a contact organo-phosphorus insecticide and is moderately toxic to bees. It is considered safe for parasitoids and predators. Its dermal LD50 is 1390 mg/kg. M/s Voltas Ltd., Mumbai, is manufacturing it in India.
Phosalone is sold under the trade names of Zolone, Rubitox, RP 11 and RP 974 in the form of EC, WP and dust. It is applied at the rate of 0.5-1.0 kg a.i. per ha in concentrations varying from 0.025- 0.1 per cent on a number of crops. It is effective against the bollworm complex, hairy caterpillars, semiloopers and leaf miners.
(xxv) Fenthion:
Fenthion (C10H15O3PS) (Fig. 7.2) was introduced in 1957, by Farbenfabriken Bayer A.G. under the code numbers Bayer 29493 and 51752. It is a systemic and contact organophosphorus insecticide. By virtue of its low volatility and stability to hydrolysis it has high persistence. It may be phytotoxic on sensitive cotton, and apple varieties such as ‘golden’ or ‘delicious’. The acute oral LD50 for male rats is 215 mg/kg and the acute dermal LD50 per male rats is 350 mg/kg. M/s Bayer (India) Ltd., New Delhi, manufacture it in India.
Fenthion is sold under the trade names of Lebaycid, Baytex, Entex and Tiguvon, and is available in the form of EC. It is applied at the rate of 625-1250 g a.i. per ha in concentrations of 0.05 to 0.1 per cent on many field crops. It is effective against the tingid bug, leaf-folders, web-worms, thrips and leafhoppers.
(xxvi) Triazophos:
Triazophos (C12H16N3O3P5) is a broad spectrum insecticide/acaricide with contact and stomach action. It is effective against aphids, thrips, lepidopterous larvae, etc. on crops like cotton, vegetables, etc. The registered formulations are 20% EC and 40% EC. The acute oral and dermal LD50 for rat is 57-68 and 2000 mg/kg, respectively. It is toxic to honey bees.
(xxvii) Chlorpyriphos:
Chlorpyriphos (C9H11Cl3NO3PS) (Fig. 7.2) was introduced in 1965 by the Dow Chemical Co. under the code number Dowco 179. It is a contact organophosphorus insecticide and acaricide especially for the control of soil pests. It persists in soil for 2-4 months. The acute oral LD50 for male rats is 155 mg/kg and the acute dermal LD50 for rabbits is about 2100 mg/kg. It is rapidly detoxified in the animal body. Motilal Pesticides (India) Pvt. Ltd., New Delhi, formulate this insecticide at Mathura.
Chlorpyriphos is sold under the trade name of Dursban and is available in the form of EC and granules. It is applied at the rate of 200-250 g a.i. per ha. As a spray it is used in the concentration of 0.06 per cent on field crops. As a soil insecticide it is used in higher doses against termites and white grubs. It is effective against black bug, tobacco caterpillar, termites, white grubs and ground weevils.
(xxviii) Disulfoton:
Disulfoton (C8H19O2PS3) was introduced in 1956 by Farbenfabrikien Bayer A.G. under the code numbers Basu 19639 and 5276. It is a systemic organophosphorus insecticide and acaricide possessing residual action for 6-12 weeks. The acute oral LD50 for male rats in 7.0 mg/ kg and the acute dermal LD50 for male rats is 15 mg/kg. M/s Bayer (India) Ltd., New Delhi, manufacture it.
Disulfoton is sold under the trade names of Disyston, Solvirex, Dithiodemeton, Dithiosystox, Thiodemeton and Disystox, and it is available in the form of granules. It is applied in the soil as a systemic insecticide at the rate of 1.5-2.0 kg a.i. per ha on a number of field crops. It is effective through the plant system against aphids, leafhoppers, leaf-miners, thrips, stem weevils and shoot flies.
III. Carbamates:
(i) Carbaryl:
Carbaryl (C12H11NO2) was introduced in 1956 by the Union Carbide Corporation under the code number Experimental Insecticide 7744. It is a contact insecticide with slight systemic properties. There is no evidence of phytotoxicity at the recommended dosage. Two distinct qualities have made it the most popular material- very low mammalian oral and dermal toxicity, and a rather broad spectrum of insect control.
The acute oral LD50 for male rats is 850 mg/kg; the acute dermal LD50 for rats is more than 4,000 mg/kg. M/s Union Carbide India Ltd., New Delhi, manufactured carbaryl at Bhopal in India. However, the factory has been closed since December 1984, when the leakage of methyl isocyanate gas resulted into the death of more than 3000 persons.
Carbaryl is sold under the trade names of Sevin, Hexavin, Carbavin and Ravagon, and is available in various formulations including WP, LVC, dust and granule. It is applied at the rate of 2.50-6.25 kg a.i per ha in concentrations of 0.1-0.3 per cent on a variety of crops including maize, cotton, gram, paddy, sugarcane, peas, jute, wheat, onions, grapes, coconut, cardamum, etc. It is effective against tissue borers, bugs, leafhoppers, midges, thrips, termites, white flies, maggots, hairy caterpillars, pests of household and external parasites of farm animals.
(ii) Carbofuran:
Carbofuran (C12H15NO3) is systemic phenylcarbamate insecticide and nematicide. Its acute oral and dermal LD50 to rat are 8.2-14.1 mg/kg and 10-20 mg/kg, respectively.
Carbofuran is sold under the trade name of Furadan and is available in the form of EC and granules. It is used at the rate of 0.75- 1.00 kg a.i. per ha and is generally used in the concentration of 0.025 per cent on various fruit crops. It is effective against tissue borers, fruit flies, aphids, white flies, thrips, leaf-miners, leaf-rollers, white grubs and ground weevils.
IV. Synthetic Pyrethroids:
Natural pyrethrins were quite effective against a variety of stored grain pests but were unstable in light and very expensive. The first synthetic pyrethroid was described in 1973 and many new photostable pyrethroids were synthesized between 1973-77. Synthetic pyrethroids exhibit high activity against insects, low mammalian toxicity, greatly increased stability, effectiveness at very low dosages, rapid action and degradation to innocuous residues.
The activities of pyrethroids to insects, mammals and other groups such as fish depend on the optical and geometrical configurations of their acidic and alcoholic components. The mobility in soil is very small. The mammalian toxicity of pyrethroids is generally lower than that of other classes of insecticides. These are more effective as contact insecticides and to a lesser extent as stomach poisons.
These can be used for ‘the control of a wide range of pests even when used at a very low dose, and being biodegradable leave no residue to accumulate in the biological systems. These can be safely applied on agricultural crops, pests of food-grains, household pests, parasites of domestic animals and livestock. Their field trials indicate that the tissue borers of many crops which are not controlled by other powerful insecticides easily succumb to the application of pyrethroids.
Cypermethrin is sold under the trade names of Ripcord, Cymbush, Cyperkill, etc. and is available as emulsifiable concentrate. It is applied at the rate of 50 g a.i. per ha in low concentrations on cotton, arhar, sugarcane, gram, lentil, coffee, etc. It is effective against the bollworm complex of cotton, pod borers of arhar, gram, lentil, etc.
Permethrin is sold under the trade names of Permasect, Ambush, etc., as emulsifiable concentrate. It is applied at the rate of 50 g a.i. per ha in low concentrations on cotton, arhar, vegetables and pulses. It is effective against the bollworm complex of cotton, tissue borers and pod borers.
Deltamethrin sold under the trade name of Decis, as an emulsifiable concentrate. It is applied at the rate of 10 g a.i. per ha against the bollworm complex of cotton, pod borers and tissue borers of fruits, vegetables and pulses.
Fenvalerate is sold under the trade names of Sumicidin, Fenval, etc. as an emulsifiable concentrate. It is applied at the rate of 50 g a.i. per ha in low concentrations against the bollworm complex of cotton, pod borers and tissue borers of fruits, vegetables and pulses.
V. Miscellaneous Insecticides:
(i) Pirate:
The pyrroles were discovered by the American Cyanamid Co., and the lead compound of this group is Pirate. This broad-spectrum insecticide/acaricide is highly active by ingestion, exhibits contact activity, and provides moderate residual activity.
Because of different mode of action (uncoupler of oxidative phosphorylation), Pirate is effective against insects such as diamondback moth and tobacco budworm which have developed resistance to carbamates, cyclodienes, organophosphates and pyrethroids. In field studies, it has provided effective control of several agricultural pest species from the orders Acari, Coleoptera, Diptera, Heteroptera, Homoptera and Lepidoptera. It is classified as moderately toxic to mammals based on acute toxicity studies.
(ii) Diflubenzuron:
It is an insect growth regulator and interferes with moulting process in the larvae leading to abnormal developments. It is effective against most leaf feeding larvae at 25-75 g a.i/ha and at 50-150 g a.i/ha against cotton boll worms. It is non-toxic to predators and honey bees. It is registered as 25% WP in India. Its oral LD50 for rat is 4640 mg/kg and dermal for rabbit 2000 mg/kg.
(iii) Novaluron:
Novaluron [1-[3-clhlaro-4-(1, 1, 2-trifluoro-2-2-trifluoromethoxyethoxy) phenyl] – 3-(2, 6-difluorobenzoyl) urea] is an insect growth regulator that inhibits the chitin formation in larvae of Lepidoptera, Coleoptera, Homoptera and Diptera. It has potent insecticidal activity against several foliage feeding insect pests. It has very low toxicity to mammals, birds and earthworms.
(iv) Cartap:
It is commonly known as cartap hydrochloride (C7H16CIN3O3S2). Its insecticidal properties were reported in 1967. It is systemic insecticide with stomach and contact action. It acts on the central nervous system by ganglionic blocking action resulting in paralysis, cessation of feeding and death due to starvation. It is effective against rice stem borer and leaf- folder, sugarcane shoot borer, cabbage diamondback moth, etc. It is registered in India as 50% SP and 4G. Its acute oral and dermal LD50 for rat is 325-345 and 1000 mg/kg, respectively.
(v) Fipronil:
Fipronil is a new phenylpyrazole insecticide that has excellent activity against many soil and foliar insect pests. Its insecticidal properties were discovered by Rhone-Poulenc Ag. Co. in 1987. This broad-spectrum insecticide is highly active via ingestion, contact and systemic routes.
It has shown a great promise both as a soil and foliar insecticide against several important insect pests of cotton. Its unique action as a potent blocker of the GABA-gated chloride channel makes it effective against insects resistant to carbamate, organophosphate and pyrethroid insecticides. Acute oral LD50 for rats is 100 mg/kg and decimal 72000 mg/kg.
(vi) Imidacloprid:
Imidacloprid (1-[(6-chloro-3-pyridinyl)-methyl]-N-nitro-2- imidazoli-dinimine) is a nitromethylene derivative synthesized in 1985 by Nihon Bayer Agrochem K.K. (Tokyo, Japan). It is a contact and systemic insecticide exhibiting low mammalian toxicity (oral LD50 = 424-475, dermal LD50=5000). With superior activity against sucking insects such as aphids, leafhoppers, planthoppers, thrips and whiteflies, it is also effective against some Coleoptera, Diptera and Lepidoptera.
Imidacloprid has a novel mode of action that is similar to nicotine; it acts as an agonist of nicotine acetylcholine receptor. With excellent systemic and good residual characteristics, it is especially appropriate for seed treatment and soil application. Effective control with long lasting protection has been demonstrated in crops such as cotton, maize, potatoes, rice, sorghum and vegetables.
(viii) Spinosad:
It is a natural source insecticide containing a mixture of two components derived from fermentation technology produced by Saccharopolyspora spinosa, a species of actinomycete. It is formulated as 48SC and is active against Helicoverpa armigera (Hubner), leafhopper, aphid and whitefly on cotton at 75-100 g a.i. /ha.
VI. Fumigants:
(i) Hydrogen Cyanide:
Hydrocyanic acid (HCN) was introduced as an insecticide by American Cyanamid Co. in 1783. It is an effective fumigant for stored grains and other commodities kept in enclosed structures. It is a highly toxic substance and at a dose of 0.04 g it is lethal to human beings. The threshold limit is 10 ppm and the LD50 is 4 mg/kg.
It is also available under the trade names of Cyclon, Cyclone B, Zacon-Discoids, Prussic acid, etc. It is available as dust, granules, and the conventional packing is in the form of pressurized cylinders. It is applied at the rate of 3.5-5.3 kg/100/m3. It is also used for tent-fumigation of citrus and other plants which should be exposed for 45 minutes at night. It is recommended for use in silos, warehouses, ships and other bulk storage structures against pests of almonds, beans, peas, peanuts and other dry fruits. It can kill all insects and rats when fumigation is allowed for 12 hours.
(ii) Methyl Bromide:
Monobromo methane (CH3Br) was introduced as an insecticide in 1932 by Dow and other chemical companies of the USA. It is a gaseous fumigant used in the soil as well as on commodities. It is highly phytotoxic. An exposure to 2000 ppm for one hour may be lethal and it also causes burns. Acute vapour toxicity is 200 ppm.
It is available as 26, 69, 98 and 100 per cent liquids and 98 per cent compressed gas. It is sold under the trade names of MB, Bromothane, Weedfume, EDCO, Tribrome and Profume. It is used for controlling several annual and perennial weeds like Johnson grass, several fungi, nematodes, parasitic plants, insects and mites.
It is used in quarantines against khapra beetle and pink bollworm larvae. It is usually applied at the rate of 1.6-6.4 kg per 100 m3. It is recommended not to carry out fumigation with methyl bromide under high moisture conditions. It does not impair germination of dry seeds when fumigated.
(iii) Ethylene Dichloride and Carbon Tetrachloride:
Carbon tetrachloride (CCl4) was introduced in 1908 by Diamond Shamrock and other chemical companies for nursery fumigation. It is mixed, usually, with other chemicals which suppress its flammability. It is generally mixed with 1, 2- dichloro-ethane (C2H4Cl2) which is primarily a fumigant and was introduced by Union Carbide Chemical Co., USA in 1927; the LD50 of carbon tetrachloride is 5730 mg/kg. Repeated exposures of the mixture to human beings are dangerous especially when alcohol is consumed. Dichloroethane is irritating to skin. Its threshold value is 100 ppm and LD50 is 890 mg/kg.
Carbon tetrachloride and dichloroethane are used in the ratio of 1: 3 to reduce fire hazards. This mixture is effective against insect pests of stored products. It should not be used on growing plants, although it has been used successfully against peach twig borer and other wood boring insects.
(iv) Ethylene Dibromide:
1, 2-dibromoethane (C2H4Br2) was introduced by Dow Chemical Co. and others in USA in 1925 as EDB. It is soil as well as stored product fumigant. The threshold value of toxicity is 25 ppm and LD50 is reported to be 146 mg/kg. It can cause burns on the skin and is phytotoxic to plants at higher doses.
It is also marketed under the trade names of Fumo-gas, E-D-Bee, Bromofume and Dowfum W- 85 as 100, 83, 75, 40 and 20 per cent solutions and 75 per cent water miscible liquid. It is recommended for use as soil fumigant on beans, crucifers, cucurbits, tobacco, tomato, etc. against nematodes which do not form cysts and against soil insects, including termites at the rate of 30-190 litres per ha. It is also used for spot fumigation of stored products as it does not penetrate deep into the grains. It is not recommended to grow crops for 7-15 days after soil fumigation. The stores are fumigated for 24 hours and then aerated.
(v) Aluminium Phosphide:
Aluminium phosphide (AIP) was introduced as a pesticide around 1955 by Degesch A.G. under the trade name of Phostoxin. It is highly insecticidal and is also a potent mammalian poison and is mainly used for the fumigation of grain.
Aluminium phosphide is sold under the trade names of Phostoxin, Celphos and Delicia, and is available in the form of solid tablets which on contact with moist air gradually release the deadly phosphine gas. It is used at the rate of 25 tablets per 100 m3 for the fumigation of infested grains, furniture, carpets or other industrial goods. If is effective against stored grain insect pests, wood borers, carpet beetles, woolly bear and other insects infesting leather, silk, cotton, jute, etc.
2. Acaricides:
(i) Chlorobenzilate:
Ethyl 4, 4′-dichlorobenzilate (C16H14C3Cl2) was introduced as an acaricide by Geigy Chemical Co. in 1952. It is a chlorinated hydrocarbon, closely related to DDT in structure. It is usually not phytotoxic but sometimes it may cause injury to peach, plum, rose and prunus. Unlike DDT, it is not accumulated in body fat. The mammalian toxicity as LD50 is reported to be 1000 mg/kg.
It is also marketed under the trade names of Folbex, Akar and Acarben as 25 per cent wettable powder or emulsifiable concentrate. It is recommended for use on fruits, cotton, cucurbits, turfs and ornamental plants against all species of phytophagous mites. It is applied at the rate of 0.75-2.50 kg per ha. Being a selective acaricide; it is used against the tracheal mites causing acarine disease in honeybees. The hives are fumigated by burning Folbex paper strips.
(ii) Dicofol:
1, 1-bis (p-chlorophenyl)-2, 2, 2-trichlor-ethanol (C14H13OCl5) was introduced as an acaricide in 1955 by Robin and Haas Chemical Co., under the trade name of Velthane. It is also related to DDT in structure. It differs from DDT only with respect to bridge 11 which is replaced by ‘OH’. It is non-systemic with long residual activity. It is non-phytotoxic. The mammalian toxicity, LD50, is 684 mg/kg.
It is marketed as EC, WP and dust. It is applied at the rate of 1.0-2.5 kg per ha on all types of plants against mites. It gives good initial kill and long residual action. Its residue disappears in soil rapidly but traces may persist for a year or more. It is compatible with most other pesticides.
(iii) A number of insecticides are equally effective against mites. These insecticides are thiometon, phorate, menazon, formothion, chlorpyriphos, etc.
3. Nematicides:
These chemicals are used for controlling plant parasitic nematodes.
Some of the common nematicides are mentioned here:
(i) Dibromochloropropane (DBCP):
1, 2-dibromo-3-chloropropane (C3H6Br2Cl) as soil fumigant was introduced in 1955 under the trade names of Nemagon and Fumazon by Shell Chemical Co. and Dow Chemical Co. It is also marketed as Memapaz and Namafume. As nematicide, it is particularly effective against root-knot nematodes when the soil temperature is 21-27°C. It is non-phytotoxic to most of the plants at normal concentrations. Some plants such as potato and tobacco are, however, sensitive to its action. It is irritating to eyes and its LD50 is reported to be 173 mg/kg.
It is available as EC and granules. The dose of its application varies from 12-30 litres per ha. It can be applied around the basin area of woody perennials. Also, it can be injected into soil or applied with irrigation water to the standing crops which are tolerant to its action. This nematicide is very effective for the control of root-knot nematodes, cyst nematodes, stylet nematodes, root lesion nematodes and other ectoparasitic nematodes present in the rhizosphere of roots.
(ii) Dichloropropane-Dichloropropene (D-D-mixture):
DD mixture is a by-product of plastic manufacture which was first used as a soil fumigant in 1943 by Dow Chemical Co. and Shell Chemical Co. Since then, it has been in use as an effective nematicide in cooler climates (4-27°C). It is a mixture of 1, 3-dichloropropane and 1, 2-dichloropropene and is phytotoxic. It is a dark liquid at ordinary room temperature.
It does not accumulate in soil and is safe for the soil microorganisms. It has quite a high mammalian toxicity, LD50 being 140 mg/kg. Its contact with skin or the inhaling of its fumes should be avoided. Its strong odour warns the operator and it should be stored away from food. Being inflammable, it should be used with great care.
The commercial names of this nematicide are DD, Vidden D and Telone. It is a liquid fumigant and can be applied to the properly tilled soil by injecting it and later plugging the holes. A crop should be sown or transplanted after a period of three weeks so as to avoid phytotoxic effects.
The dosage varies from 200 to 400 litres per ha. It is very effective for the control of cyst nematodes, Heteroderci and Globodera spp., the root-knot nematodes, Meloidogyne spp, the burrowing nematodes, Rapopholus similis and the root-lesion nematodes, Pratylenchus spp.
(iii) Ethylene Dibromide:
Chemical and biological properties have been described in the section on ‘Fumigants’. Its trade name is Dowfume W-85. This fumigant is in liquid form and should be applied by injection method upto a depth of 15 cm in rows 25-40 cm apart. The dose per hectare is 250 kg. After soil fumigation, a crop should not be sown or transplanted before a waiting period of 3 weeks in order to avoid phytotoxic effects. It can be employed for the control of the root-knot, the root- lesion and cyst nematodes.
(iv) Ethoprop:
It is marketed under the commercial name of Mocap by Mobile Chemical Co. and is available in granular or EC form. It is applied at the rate of 2.4 kg/ha.
(v) Phenamiphos:
It is commercially available under the name of Nemacur, and its formulations are both granular and EC. It is very effective for the control of root-knot and cyst nematodes. Being a systemic nematicide, it is capable of killing both ecto- and endo-parasitic nematodes. The application rate varies from 5 to 10 kg a.i. per ha and it can be applied before or at the time of sowing or transplanting a crop.
(vi) Metham Sodium:
Sodium N-methyl dithiocar-bamate dihydrate (C2H4NS2Na.2H2O) was introduced in 1954 by Stauffer Chemical Company and E.I. Dupont de Nemours, under the trade name of Vapam. It is a soil fumigant for the control of fungi, bacteria, nematodes, weeds and soil insects. It is phytotoxic and in gaseous form, is irritating to eyes, skin and mucous membranes. The LD50 is reported to be 1260 mg/kg.
It is also sold under the trade names of Vitafume, Unifume, Sistan, Trimaton and Mapsol. It is available in water miscible form and the breakdown product is methyl isothiocyanate. The soil application is by injection method and it should be applied 2-3 weeks before transplanting the crop. The dose varies upto 1000 litres per ha. It controls the root knot and lesion nematodes. It is not advisable to use this chemical in green houses. It is corrosive to brass and copper.
(vii) Methyl bromide (CH3Br):
Chemical and biological properties of this compound have been described under the section on ‘Fumigants’. It is a gas fumigant and is available under the trade names of Embafume-C and Dowfume MC-2. Dowfume MC-2 is a formulation of bromomethane and 2 per cent chloropicrin. It should be applied in the soil before transplanting or sowing of a crop at the rate of 100-440 kg per ha under a gas-tight cover. It is a broad spectrum nematicide and kills all types of plant parasitic nematodes.
(viii) Qamyl:
The commercial name of the chemical is Vydate. It is available in the form of granules and it is an emulsifiable concentrate. The granules can be applied by broadcasting in the field before sowing or at the time of sowing. Emulsifiable concentrate can also be sprayed on plants for the control of stem and bulb nematodes and also root-knot nematodes infesting vegetable crops.
(ix) Aldicarb:
Aldicarb (C7H14N2O2S) (Fig. 7.3) was introduced as an insecticide-acaricide – nematicide in 1962 by Union Carbide Corporation, USA. It is systemic in nature and at the recommended dose it does not damage seeds. It is highly toxic to mammals and the LD50 is only 0.93 mg/ kg. It is marketed under the name Temik and is formulated as granules having 5 and 10 per cent active ingredient.
It is very effective at the dose of 2-4 kg a.i. per ha and can be broadcast or drilled at the planting sites. The root-knot, the cyst, the root-lesion and citrus nematodes can be controlled effectively. It has no phytotoxic effects and hence can be applied on vegetable crops quite safely.
(x) Carbofuran:
Chemical and biological properties of carbofuran (Fig. 7.3) have been described under the section on Carbamates. It is available in granular and flowable formulations under the commercial name Furadan. The recommended dose is 2 to 4 kg a.i. per ha for the control of root- knot and lesion nematodes infesting vegetable crops. Flowable powder can be applied as seed treatment to provide protection to the newly emerging seedlings.
(xi) Dazomet:
Dazomet (C5H10N2S2) was introduced by Union Carbide Corporation, USA, in 1952, as a pre-plant soil fumigant under the trade name of Mylone. It is reported to be phytotoxic to growing plants. It is the break down product, methyl isothiocyanate, which is toxic to nematodes. Dazomet is irritating to skin and the mammalian toxicity as LD50 is reported to be 500 mg/kg.
It is also marketed under the trade names of Basamid, DMTT and Soil-Kare. It is available in the form of 50 and 85 per cent WP, 50 per cent granules, and 2 and 5 per cent dusts. It is recommended for use on tobacco and ornamental plants at the rates of 200-500 kg per ha. It controls all nematodes except the cyst forming nematodes. Since it is phytotoxic, it is applied 4 weeks before planting. It also kills some weeds.
(xii) Fensulfothion:
Fensulfothion (C11H18O4PS2) was introduced as a soil insecticide and nematicide by Farbenfabriken Bayer, A.G. of Germany in 1964 under the trade name Dasanit. It is systemic and long-persistent. It is non-phytotoxic at the doses recommended for use. It is a highly toxic compound and the mammalian LD50 is reported to be 2.2 mg/kg.
It is also sold under the trade names of DMSP and Terracur-P. It is available as emulsifiable concentrate and granules. It is recommended for use on cruciferous vegetables, tobacco, tomato, potato and ornamental plants. It is recommended for the control of root-knot and golden nematodes, when applied at the rate of 1-16 kg a.i. per ha. It protects the plants against soil insects and nematodes for 4 months. It should not be applied on the foliage or in the green houses. It is also toxic to fish in water.
(xiii) Phorate:
The chemical and the biological properties have been described under the section on ‘Organophosphorus Insecticides’. It is also a granular nematicide and is available as Thimet. For the control of root-knot and other ectoparasitic nematodes, it is recommended at the rate of 10 kg a.i. per ha. It is applied by broadcast method and then mixed into the soil.
4. Rodenticides:
(i) Strychnine:
Strychnine (C20H20N2O) was used as a rodenticide in Europe around 1930. Chemically, it was synthesized in 1954 in USA and was distributed by a number of companies. It is of botanical origin and was extracted from the seeds of Strychnos spp. It is a strong mammalian poison; the LD100 for rats is 1-30 mg/kg and for man is 30-60 mg/kg. The threshold limit is 0.15 ppm.
It is sold under the trade names of Sanaseed, Mousetox, Kwik-kill, Rodex, etc. It kills mice, squirrels, dogs, porcupines, rabbits, jackals, birds and other animals. It is marketed as a concentrated powder which is used for making baits. It is mixed with raw meat as a bait to kill jackals. It can also be used by mixing it with grains, vegetables or fruits at the rate of 0.5 per cent by weight. Since it is a deadly poison, its handling needs utmost care by the users. One application is usually sufficient to kill the animals.
(ii) Zinc Phosphide:
Zinc phosphide (Zn3P2) was introduced by Hooker Chemical Co. in 1943. This rodenticide belongs to inorganic phosphide group and has long been in use. It is an acute poison for mammals and birds. It is stable when dry, but decomposes slowly to phosphine in moist air. It is a general poison and the mammalian toxicity at LD50 is reported to be 45.7 mg/kg. It is sold under the trade names of Rumetan, Mous-con and Kilrat as 80-95 per cent concentrated powder.
It is usually used in the concentration of 2.5 per cent as bait for killing field rats, mice and other rodents. The bait is prepared by mixing one part of zinc phosphide with 40 parts of wheat- flour, adding sufficient water to make pellets. Alternatively, the poison can be coated on grains of wheat, maize, sorghum or bajra (the pearl millet, Pennisetum typhoides) after they are rinsed with a small quantity of some edible oil. It is an acute poison and only one dose is needed to kill the animal. The disadvantage of this compound is that rats come to know of its presence and they develop bait shyness.
(iii) Warfarin:
Warfarin (C19H16O4) is the first anti-coagulant coumarine derivative which was synthesized by Wisconsin Alumni Research Foundation in 1950. It was sold by S.B. Penick and Co. and Prentis Chemical Co. The mammalian toxicity as LD50 is reported to be 186 mg/kg as a single dose. On a multiple dose basis, the LD100 for rats is reported to be 0.2 mg/kg/day, for 5 days.
It is sold under the trade names of Rat-B-Gon, Warf, Warfarat, Dethmor and Duocide in numerous formulations such as concentrated powder, dust, bait, water miscible liquid, etc. It is used to kill rats and mice. The rats die of internal haemorrhage after eating it for about 5 days. It is applied in cereal baits at the rate of 0.025-0.05 per cent by weight.
The 0.5 per cent powder is mixed with dry bait material at a 19: 1 ratio to get the required concentration. It should be kept out of the reach of children, pets and other domestic animals. Vitamin K is an antidote. The other commonly used anticoagulant is Fumarin sold as Rodafarin and Ratafin.
5. Molluscicides:
Molluscicides may be classified into two broad categories, viz. aquatic and terrestrial. Aquatic molluscicides may be botanical, e.g. endod, or chemical, e.g. copper sulphate, niclosamide, sodium pentachlorophenate, tritenmorph,etc.TerrestriaI molluscicides include carbamates, i.e. aminocarb, carbaryl, isolan, methiocarb, mercaptodimethur, mexacarbate, etc. and others, i.e. metaldehyde.
Metaldeyde (plymer aldehyde) is also known as metacetaldehyde and by the trade name Meta. The slug killing properties of metaldehyde were reported in 1936, slugs are immobilized before they die. It is formulated as slug bait in a protein rich milling offal such as bran. Ordinary lime is also used as a molluscicide by sprinkling it on the ground, around the cropped area.