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Economic Potential of Biological Substitute for Chemical Pesticides with Special Reference to IPM
1 INTRODUCTION
During the last three and half decades of the twentieth century, the productivity of the Indian agriculture increased dramatically. This remarkable increase resulted from an intensive use of high yielding seeds, fertilizers, pesticides, and water. The yield-augmenting technological change led to self-sufficiency in food production. Yet, the concerns of food security have not diminished altogether. Foodgrain production in India has to increase at least 2 million tonnes a year to meet the food security needs of the growing population ( Pawar ). A number of biotic and abiotic factors continue to constrain the growth in the agricultural productivity. Insect pests, diseases and weeds are the main yield-limiting factors in most parts of the world. A significant proportion of the potential agricultural production is lost due to pests. Forty two percent loss in the global output due to insect pests, diseases and weeds, despite use of various plant protection tactics. The loss could have increased to 70 percent if the pests were left uncontrolled.
Farmers use a number of pest control strategies to limit the crop loss. Chemical pest control has, however, been the preferred strategy in practice in India since the beginning of the green revolution era in 1965-66. In 1955-56 consumption of pesticides in agriculture was about 15 gm/ha, it increased to 90 gm/ha in 1965-66. In 1990-91, the pesticide use reached a peak of 405 gm/ha, and has been declining afterward and at present it is 250 gm/ha. Notwithstanding their success in controlling the insect pests, diseases and weeds, pesticides adversely affect public health and environment. The ill effects of pesticides on the public health and ecology are numerous. Direct exposure to the pesticides can induce allergies and affect body organs. Residues of the pesticides in foodgrains, fruits and vegetables, fish, milk, water and soil have often been reported to exceed their acceptable limits Empirical evidences suggest that the cost of the measurable negative externalities of the pesticides outweigh their perceived economic benefits
Pesticides are broad-spectrum toxic chemicals. These, besides limiting the pest populations, also adversely affect the populations of the beneficial insects and the microorganisms, predatory birds and the natural enemies of the insect pests Indiscriminate use of the pesticides has resulted into problems of the pest resistance, resurgence, secondary outbreaks. Worldwide, about 504 insect pests, 273 weed species and 150 plant pathogens have developed resistance. These are serious obstacles to raising the agricultural productivity. Repeated applications of pesticides to overcome these problems increase the cost of pest control.
In India, insect pests such as Helicoverpa, white fly, diamond back moth, tobacco caterpillar and mustard aphid have developed resistance to almost all the pesticides intended to control them. Outbreak of Helicoverpa in 1988 in cotton growing regions of Andhra Pradesh caused loss in cotton production equivalent to15 percent of state’s agricultural gross domestic product. Obviously, the crop losses due to pests have increased. Information on trend in crop losses though is scarce; scattered evidences indicate considerable increase in crop losses. In traditional agriculture, about 3 percent of rice,10 percent of wheat, 18 percent of cotton and 5 percent of oilseeds output was estimated to be lost due to insect pests. In early 1990s the loss increased eight-fold in case of rice, three-fold in case of cotton and seven-fold in case of oilseeds. With rising public concerns about the economic and ecological externalities of the chemical pesticides, the emphasis of plant protection research and development strategies has been gradually shifting from chemical to non- chemical approaches (mainly biological). Research has generated new technologies, using naturally occurring enemies of insect pests (parasitoids, predators and pathogens). Some important commercially available products are: Trichogramma, Bracons, Crysoperla carnea, Crytaemus montrouzieri, Bacillus thuringiensis, Bacillus sphaericus, Nuclear polyhedrosis viruses (NPV) and Trichoderma. In addition, a number of plant products such as,azadirachtin (neem), pyrethrum, nicotine etc, are also valuable as biopesticides. In India, more than 160 natural enemies have been studied for their utilization against insect pests
Environmental and public health benefits of the biological pest management are well documented. And, most of the biological technologies are claimed to be effective against the insect pests, diseases, and weeds, particularly when it applied in conjunction with other methods including chemical pesticides, agronomic practices and mechanical control. Such a strategy is referred to as Integrated Pest Management (IPM).
Plant protection in india: strategies and policies
In the pre-green revolution era, Indian farmers had been using a number of non-chemical methods of pest control. Use of chemical pesticides started with the import of DDT after World War II for the control of malaria. By the end of the First Five Year Plan, the pesticide use in agriculture was 15 gm/ha. In 1966, with the introduction of high yielding varieties of rice and wheat, the usage of pesticides had reached 94 gm/ha. Since then pesticide use has increased tremendously. At the end of the first decade of introduction of new varieties, the pesticide use in agriculture has increased to 266 gm/ha. Pesticide consumption kept on increasing till 1990-91, but started declining afterwards. At present, pesticide consumption is estimated about 250 gm/ha.
Crop Loss due to Pests
About 50 percent of the potential output of cotton and 25 percent of rice is lost due to pests. Production loss due to pests in pulses and sugarcane is estimated at 30 and 20 percent, respectively. In case of coarse cereals, 25-35 percent of their potential production is lost due to pests. Loss in oilseeds too is also high. Loss in wheat is reported about 15 percent.