Classification and Characteristics of Some Major Pesticides
Pesticide is any agent used to kill or control undesired insects, weeds, rodents, fungi, bacteria, or other organisms. These are derived from various chemicals and they contain different elements. Hence, in general any pesticide shall be classified based on the pest they kill and based on the chemical groups they contain. Table M-IX 1.3 and Figure M-IX 1.5 shows the block diagram for classification of pesticides . Apart from this, pesticides can be basically characterized by their physical, chemical and toxicological properties. Toxicity may be acute or chronic and it depends on type and dose of pesticide taken and mode of intake. Table M-IX 1.4 gives the characteristics of some major pesticides.
Table M-IX 1.3: Technical Grade Pesticide Manufacturer in India
Name of Pesticides
Acephate, BHC, chlorpyriphos, Cypermethrins, DDT, Dichlorvos, Dimethoate, Deltamethrin, Dichloropropane&dichloropropanes, mixture (D.D. mixture), Dicofol, Ethion, Endosulfan, Ethylene dibromide& carbon tetra chloride mixture, Fenthion, Fenitrothion, Fenvalerate, Lime- sulfur, Lindane, Malathion, Methyl parathion, Monocrotophos, Nicotine sulphate, Oxydemetonmethol, Phosphamidon, Pyrethrum extract, Phorate, Phosalone, Quinalphos, Temephos, Triazaphos.
Aureofungin, Copper oxychloride, Copper sulphate, Carbendazim, Captafol, Ferbam, Mancozeb, Nickel Chloride, Organomercurials (MEMC & PMA), Sulphur (Colloida, wettable and dust), Streptocycline, Thiram, Tridemorph, Ziram, Zineb.
Barium carbonate, Comafuryl, Sodium cyanide, Warfarin, Zinc phosphide.
Anilophos, Butachlor, Diuron, 2,4-D, Fluchlorallin, Glyphosate, Isoproturon, Paraquat dichloride.
PLANT GROWTH REGULANTS
Alpha naphthalene acetic acid, Chloromequat chloride.
Aluminiumphasphide, Ethylene bromide, Methyl bromide
Figure M-IX 1.5: Block Diagram of Classification of Pesticides
Table M-IX 1.4: Characteristic of Some Major Pesticides
Insecticide, colorless white crystal, odorless or slight aromatic odor BP=109OC , TLV=1mg/m3 of air
Vomiting, numbness, partial paralysis, mild convulsions
Insecticide , yellowish liquid BP=3750C
Headache, blurred vision, weakness, nausea, cramps, sweating, loss of reflexes, coma
Herbicide, white powder, mol wt.- 221
Nausea ,vomiting ,kidney and liver failure
Insecticide , solid, melting point=1420C ,TLV=5mg/ m3 of air,
Symptoms same as parathion but to a lesser extent
Crystalline, melting point=1500C
Headache, nausea, vomiting, general malaise and drowsiness
White crystalline powder, melting point=1570C
Irritation, excitation, hyperirritability, loss of equilibrium, depression
White crystalline powder, melting point=1570C,Mol wt. =290.84 TLV=0.5 mg/m3of air
Acute toxicity may be excitation, hyperirritability, and loss of equilibrium, depression, headache, nausea, irritation of eyes, nose and throat no chronic toxicity as such. It emits highly toxic fumes of phosgene when heated.
Crystalline, soluble in water, alcohol and chloroform
Relatively low toxicity but a possible carcinogen. It emits dangerous fumes when strongly heated.
Crystals, slightly water soluble but soluble in organic solvents, mol wt. =317.3, MP =740C
Highly toxic: toxicity is almost same as that of parathion.
Yellow liquid, BP=156- 157OC,slightly soluble in water, miscible with most polar organic solvents, combustible,
Toxic by ingestion and inhalation, absorbed by skin
TLV=10mg/m3 of air
Fungicde, bluish green powder,
soluble in acids, ammonia. Insoluble in water
Toxic by ingestion and inhalation
Fungicide, white and odorous when
pure ,sp gr.- 1.71, MP=2460C, insoluble in water , soluble in some solvents like acetone and carbon
Moderately toxic, strong irritant to eyes and mucous membrane
Rodenticide, Dark grey gritty powder, sp gr.- 4.55, MP>2460C,insoluble in alcohol, soluble in acids, decomposes in water.
Highly toxic by ingestion, reacts violently with oxidizing agents, Phosphine is produced when reacted with the acids.
Insecticide , brown to white crystalline solid, insoluble in water , soluble in most organic solvents, MP=104 -105 0C,
TLV=0.25mg/ m3of air
Highly toxic by ingestion and inhalation, carcinogen, use restricted to non-agricultural application.
Insecticide, white solid,
MP=51 -52 0C, moderately soluble in water, soluble in most organic solvents except hydrocarbons.
Highly toxic, a cholinesterase inhibitor, restricted use.
Diphenyl Dichloro Trichloethane (Ddt)
DDT one of the commonly used organo chlorine pesticide were synthesized first in 1874 and played important role in elimination of malaria and used for agricultural purpose. However, due its persistent nature and carcinogenic nature DDT has been banned in most of the country. DDT dissociates in presence of moisture into DDE and DDD which are highly persistent.
DDT is mixture of two isomers p,p (1-trichloro-2,2-bis (pchlorophrnyl) ethane) and o,p (1-trichloro-2-0,chlorophenyl ethane2-bis (pchlorophrnyl ethane). The former is the main constituent process steps involved in the manufacture of DDT are:
Growing environmental concerns and consumer inclination towards chemical free crops especially food crops there has been increasing use of bio-pesticides. Three major classes of biopesticides are microbial pesticides, biochemical pesticides and plant incorporated pesticides Bio-pesticides getting importance as they are less toxic than conventional pesticides which has become serious threat to environment due to its increasing use. Bio-pesticides affect only the target pest and closely related organisms.
Several factors such as new products, end user acceptance and acceptance of substitutes to conventional pesticides and declining market for harmful organophosphate insecticides, have fueled the market growth. Delivering a better alternative to manage harmful insects, weeds and fungal plant pathogens, bio-pesticides is poised to witness robust gains in coming years. The United States represents the largest region for bio-pesticides worldwide. Europe represents the fastest growing regional market for bio-pesticides.
With the growing acceptance of bio-pesticides as an efficient crop protection alternative with eco friendly footprint, several agricultural chemicals are leaning towards bio-pesticides (Global Industry Analysts, Inc)
Some of the important bio-pesticides are:
As the organic food business is growing, demand for non-toxic pesticide for crop protection is increasing. Use of bio-pesticides is being encouraged by Govt. of India as part of integrated pest management programme.
New Generation Insecticides: Looking to environmental hazards of chemicals used as pesticides in the past, new generation of pesticides with reduced risks to the environment and human health has developed and are being used. These pesticides tend to be rather surgical in method of their redicing number of insects. Some of the new generation pesticides are Neoniconoids, Spinosyns and Spimosoids, Indoxcarb, Fiproles or phenylpyrazoles, pyrazolesa, pyridazinones, quinazolines. Seven classes of insecticides which have appearance in recent years are Methyxyacrylates, npahthoquinones, Nereistoxin, Nereistoxin analogues, Pyridine azomethine, Pyrmidinamines, Tetronic acids, Clofentezine
Insect Growth Regulators (IGRS): IGRS are compounds which alter the normal growth of process of insects and therefore can be used to control insect populations. Some of the IGRS are Juvenile hormone based insecticides, Tebufenozide, Fenoxycarb