Pesticides

Insects have more species ( over million already described ) than any other for of animal life and are in many ways to most indestructible form. About 1 percent of the species offer hazard to humans ans animals , but this means that the US harbour 600 troublesome species. Humans and pests fight a continuous battle for food and shelter; insects alone claim about 10 percent of crops in the US , and about 14 percent worldwide. Various misery-causing diseases are carried by insects : malaria yellow fever, typhus, and plague to name a few . For us to survive at current population levels , pesticides must be used and new ones constantly developed. When insecticides are applied widely , all about few of the local insects are destroyed, but the remaining ones are those most resistant to the destroying agents. After several generations , this selection makes the surviving insects increasingly resistant to the destroying agent. Eventually complete resistant may occur

Safety Regulations

Chemistry pervades every area of agribusiness. The use of chemicals was limited to about 50 compounds in 1940; now several hundred are used in perhaps 50,000 commercial formulations . Effectiveness and economical production are important , but safety to farmers , consumers and the general public is so important that federal laws strictly demand it. The following specif regulatory legislation applies :

1.  The Meat Inspection Act of 1906 (as mended)
2.  Food, Drug, and Cosmetic Act of 1938 (as a mended by the Miller Amendment of 1954)
3. Agricultural Marketing Act of 1946
4. Insecticide , Fungicide and Rodenticide Act of 1957
5. Poultry products Inspection Act of 1957

Registration with the Environmental Protection Agency (EPA) is now required for all pesticides.

Insecticides

Insecticides are agents for destroying insects and are generally classified by their mode of action. Stomach poisons are lethal to insects which ingest them; contact insecticides kill following simple bodily contact; fumigants act on the insect's respiratory system. Examples of insecticides are

1.  Sulphur and Sulphur compounds
2. Pyrethrins
3. Nicotine
4. Rotenone
5. Carbophos
6. Carbaryl
7. p-Dichlorobenzene
8. Dimethoate
9. Methiocarb
10. Dichlorovos

Attractants and Repellents

Food baits combined with toxicants are attractive because they allow control over the location of the poisons rather than scattering them about . Sex attractions (phermones) are being synthesised in increasing numbers and are expected to aid in the control of several major pests. The gypsy moth sex phermone is cis -7,8-epoxy-2-methyloctadecane and is available commercially , as are several other phermones. Sex lures draw the males , which are subjected to a chemosterilant, thereby halting reproduction. Most sterilants are derivatives of aziridine.

Fumigants

Fumigants are chemicals that emit poisonous vapours. Several compounds are of value in controlling soil-infesting insects; chloropicrin which is a highly irritating ,carbon disulphide , now  seldom because of fire hazard; methyl bromide , which is accompained by application problems; and ethylene bromide , which is effective in the control of wireworms. These halogenated alkanes comprise the bulk of the soil fumigants sold. Crops in storage , particularly grains and seeds, may become infested with insects , rodents, and microorganisms . Fumigants are also employed for packaged goods. Serious infestations , such as the Mediterranean fruit fly in California , are contained by fumigating all suspected outgoing produce.

Nematicide

Nematodes are controlled by soil fumigation, but their life cycle and methods of control are not as well understood as those of other pests. Soil-contained pests are difficult to reach . Besides soil fumigants, the phosphorothioates are used for direct control.

Rodenticides

Rodenticides are used to control certain pest animals such as mice, rats, groundhogs, squirrels, and field rodents because of their ability to do extensive property damage and to spread disease. Rodents alone cause damage in the US of over 1000 million dollar annually.
Compound 1080 , Sodium monofluoroacetate , is a significant product , deadly to everything including humans. It is made by reacting ethyl chloroacetate and potassium fluoride in an autoclave at 200 Celsius. The resulting fluoro acetate is saponified with a methanol solution of NaOH , and the product crystallized out. Zinc phosphate an older compound is also used for the same purpose . Thallium sulfate is effective against number of rodents.

Fungicides 

Fungicides , including slimicides and wood preservatives , account for approximately 10 percent of pesticides sales. They are active against fungi, parasitic plants comprising molds, mildews, rusts, roots and stem rots , smuts, mushrooms, and allied forms capable of destroying higher plants, fabrics, and some plastics.Fungicides for plants act by direct contact and often injure the plants as well as the fungus.
Inorganic fungicides includes Bordeaux mixture , effective for most ordinary molds and mildews. Organic fungicides includes dithiocarbamates, chlorinated phenols and caboximides and formalin.