Different sort of pest management practices are used by farmers to protect the crop from the invasion of the pests. Insecticides are highly popular because it gives relatively quick results to enhance the production both in quantative and qualitative terms, ultimately increasng their income. DDT (Dichloro Diphenyl trichloroethane) is a synthetic chemical discovered by Othmer Ziedler in 1874 but its insecticidal property was discovered after a gap of 65 years by Paul Muller of Switzerland in 1939. This discovery was like a miracle and gave revolutionary control over insects and pests. It was effective to control diseases of human and other mammals which were transmitted by insect vector by managing the insect vector.
World War II was first US war in which diseases transmitted by insect vector like malaria (vector Anopheles spp.), typhus (vector fleas) resulted less human loss than bomb and bullet due to DDT. It also became popular among the farmers because it killed the most of insect and pests except some beetle (coleoptera), grasshopper (orthoptera) and aphid (hemiptera) of crop and generally did not show phytotoxic effect to most of the crops except tomato, cucurbit etc. In 1948 Paul Muller awarded by Nobel Prize in Physiology or Medicine for his discovery of wonderful chemical properties of DDT. It is an organochlorine group insecticide which has potent non systemic, stomach and contact action.
DDT persists for long time in the plant, soil and also accumulates in fat bodies of birds, fishes and mammals and is also secreted in milk. It also causes cancer, male infertility etc. The effect of DDT was too dangerous however probably in 1946 two scientist Elmer Higgins and Calarence Coltam published an article about tendency of DDT to accumulate in the fatty tissue of animals which caused health hazard. But since the time of World War II DDT hailed as “saviour of mankind” and “alternative and better choice than pyrethrum” to control mosquito so the widespread use of DDT was continued and no positive response was received by this article.
An American ecologist who was also known as “a bird lover – a cat lover- a fish lover- a priestess of nature”, Rachel Carson described the effect of DDT upon wildlife in her book “Silent Spring” in 1962. She wrote about how the reckless use of pesticide was contaminating the natural environment and slowly poisoning living thing. She described that only exposure of DDT reduces the reproductive potential of birds and if it ingested by bird laid thin shell egg which rarely survives.
Hungary became the first country that banned the application of DDT in agriculture followed by Norway and Sweden. On 14th June 1972, EPA (Environmental Protection Agency) announced that application of DDT in agriculture would be illegal from 31st December, 1972 in US. By 1991 at least 26 countries announced complete ban on DDT, which meant it would not be manufactured, imported, exported or used for any purpose. In India DDT was used extensively and legally in agriculture till 1989 while other countries phased it out from agriculture. It is unfortunate that India produces nearly 6000 tonnes of DDT annually for medical purposes to eradicate mosquito, even when mosquitoes developed resistance against DDT. Also, State governments run mosquito eradication programme by spraying DDT once or two times in a year. The DDT ingested by aquatic organism like small planktons (floating organism) when consumed by fish, gets accumulated in the body of fish and from these fish to large fish, bird and human. As the tropic level increases in a food chain, the amount of toxic (DDT) also increases this phenomenon called as biomagnifications. But it is good news for all Indian that the story of persistence and highly biomagnified insecticide DDT which causes health and environmental hazard will be describe on the page of history only since the year 2020 according to an agreement of India with US in 2015.
Contributed by :
Sudeepa Kumari Jha
Ph.D.(Ag.) Entomology, Scholar
BAU, Kanke Ranchi (Jharkhand) 834006
Mobile No. 8678006795