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Chemical control needs effective government. Discuss the use and abuse of pesticides of modern agriculture.

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Introduction

AS Level Biology Essay - Chemical control needs effective government. Discuss the use and abuse of pesticides of modern agriculture. Rachel Miller L6T Today, pesticides are widely used as a way of maximising the output of crops and animals in agriculture. By growing or maintaining large populations of one species of animal or crop plant in one particular area, a large food supply is created for other organisms such as insects. These other organism's populations are then allowed to become much bigger than they would normally be. These organisms rapidly become pests diminishing the yields of the cultivation. As world hunger is a problem that is prevalent today, to be able to maximise world food production is an important issue that needs close attention, and any possible solution to this problem should be considered. Estimates indicate that without the problem of insect pests alone, world food production would increase by about a third; as this represents the loss with the current control measures, it would indisputably be disastrous if control of insect pests alone was not attempted. ...read more.

Middle

Furthermore weeds can prove toxic to animals that graze on the land. Herbicides make up the majority of pesticides used today, and also seldom cause serious environmental damage. They are important for the control of weeds and furthermore the farmer no longer has to turn the soil or till it before use. This reduces the risk of soil erosion, and saves time, money and effort There is a range of herbicides with different actions on weeds: * Pre-emergence herbicides - used before the plant grows. For example, Paraquat is very toxic and will kill any plant above the ground that it comes into contact with. Yet it is broken down before any crop plants emerge from the soil. * Post emergence herbicides - sprayed over the crop plants, killing only weeds (being selective). The best known ones are the phenoxy compounds, e.g. 2,4-D (2,4-dichlorophenoxyethanoic acid), 2,4,5-T (2,4,5-trichlorophenoxyethanoic acid) and MCPA (2-methyl-4-chlorophenoxyethanoic acid). These are used against broad-leaved plants (dicotyledons), not those such as grasses and cereals (monocotyledons), and use natural plant growth regulators (synthetic auxins) ...read more.

Conclusion

These include pyrethrins extracted from the flowers of the African daisy Pyrethrum cinereafolium, and nicotine from the tobacco plant Nicotiana tabacum. Substances have been synthesised to act as insecticides. These fall into four categories: pyrethroids, organochlorines, organophosphates and carbamates. There are many problems with using pesticides. The over-use of pesticides has led to a number of ecological problems. Insects have developed that are resistant to pesticides, the toxicity to non-target species, pest resurgence, pesticide persistence and mobility within the environment and bioaccumulation within an ecosystem; as discussed previously. When strains of insects appear which are resistant to a pesticide they have a superior advantage over the non-resistant insects (as long the particular pesticide they are resistant to is in use). While the non-resistant organisms are killed, the resistant insects will increase in numbers as competition is reduced. This is very common; as in the 1940s DDT was used extensively to success, in the 1950s DDT was used in the fight against insect-bourne diseases, only to discover that many insects had evolved strains resistant to DDT. By 1987, over 500 species of insect had been identified as resistant to one insecticide or another. ...read more.

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