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第一段
1 .Good evening.
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2 .I'm here today to present the findings from our research into pesticides and alternatives to using them.
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第二段
1 .I'd like to begin by talking about some of the environment effects of pesticide use.
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2 .As most of you will be aware, pesticides have proven to be very harmful to our environment.
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3 .The principal reason for this is because nearly all pesticides along water channels such as rivers, where they are then transported downstream.
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4 .In order situations, particularly when they are dropped by plane,
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5 .the wind blows pesticides into wild areas where they are not wanted. These areas can be up to several kilometers away.
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第三段
1 .We also need to think about the effects of pesticides on animals.
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2 .Pesticides can cause illness and even death in many animals, including birds and aquatic life.
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3 .Animals can also be affected, however, when pesticide use eliminates their food source and causes them to starve or migrate to other areas.
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第四段
1 .When pesticides don't travel into neighbouring environments,
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2 .they tend to seep into the soil.
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3 .There they degrade the quality of the soil and in addition, they can weaken biodiversity -studies of pesticide - contaminated soil show a much lower count of organisms compared to healthy soil.
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第五段
1 .There's a final consideration to take into account,
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2 .and that's the environmental effects of pesticides in terms of pest numbers.
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3 .In the short term, pesticides significantly reduce the number of pests in an area, as might be expected.
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4 .After long-term, regular use, however, insects tend to become immune to certain kinds of pesticide and are no longer negatively affected by them.
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5 .As the number of insecticide resistant pests grows, this creates the need for new varieties of pesticide,
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6 .and further exacerbates the pesticide problem.
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第六段
1 .Let's move on now to look at some possible alternatives to pesticide use.
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2 .As l' II explain, although these techniques can help reduce our dependence on pesticides,
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3 .they do have their own drawbacks too.
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第七段
1 .The first technique will be familiar to any of you who have even a small vegetable garden at home.
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2 .You see a slug on a piece of lettuce,
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3 .and what do you do? Put on some gloves, walk right up to the plant and pick the slug off with your hands.
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4 .This is called handpicking.
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5 .Handpicking is remarkably effective and requires little in the way of money to implement.
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6 .But while it may be sufficient for the home gardener,
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7 .the time-consuming nature of handpicking makes it unsuitable for large-scale operations.
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第八段
1 .Owners of larger crops and orchards require a more systematic approach to pest management,
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2 .and they have a few options here.
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3 .You may be familiar with a technique known as biological control.
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4 .This involves the strategic use of what we call 'good'insects - that is,
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5 .insects which eat pests, rather than plants. When they eat the pests,
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6 .they also protect the crop environment.
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7 .Unfortunately, biological control is always risky because we can never know for sure how insects will behave in a particular environment,
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8 .and the results are therefore unpredictable.
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第九段
1 .A safer option is companion planting,
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2 .where certain plants are grown together.
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3 .Garlic, for example, fends off spider mites and aphids,
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4 .and basil drives away the tomato hornworm,
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5 .making it a good companion for tomatoes.
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6 .This is because some varieties of plant can repel specific breeds of insects,
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7 .so planning them alongside and around more vulnerable vegetables will discourage the insects from coming near.
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8 .Of course, all these extra plants begin fighting for space and
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9 .competing with the protected plants for access to water
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10 .and nutrients in the soil.
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第十段
1 .A final possibility is crop rotation. This involves alternating plants every harvest,
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2 .which forces insects to migrate in an attempt to locate their food source.
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3 .Crop rotation is unappealing for large-scale commercial operations, however, because the high cost of constantly changing crops cuts into their profits.
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第十一段
1 .As you can see, there's still no easy answer to the question of how to keep plants free from the scourge of pests.
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2 .I'm happy to take any questions...
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