Developing Sustainable Pesticides
题目：
Pesticides are substances used to get rid of insects or other pests. A pesticide gets a bad name if, as is usually the case, it kills more species than just the ones at which it is aimed. It may then become a pollutant. However, in the context of the sustainability of agriculture, its bad name is especially justified if it kills the pests’ natural enemies and so contributes to undoing what it was employed to do. Thus, the numbers of a pest sometimes increase rapidly some time after the application of a pesticide. This is known as “target pest resurgence.” It occurs when treatment kills both large numbers of the pest and large numbers of their natural enemies. As a result, pest individuals that survive the pesticide or that migrate into the area later find themselves with a plentiful food resource but few, if any, natural enemies.
The aftereffects of applying a pesticide may involve even more subtle reactions. When a pesticide is applied, it may not be only the target pest that resurges. Alongside the target are likely to be a number of potential pest species that had been controlled by their natural enemies. If the pesticide destroys these, the potential pests become real ones-and are called secondary pests. A dramatic example concerns the insect pests of cotton in Central America. In 1950, when mass dissemination of organic insecticides(a subclassification of pesticides that kill insects) began, there were two primary pests: the Alabama leafworm and the boll weevil. Organochlorine and organophosphate insecticides were applied fewer than five times a year and initially had apparently miraculous results-yields soared. By 1955， however, three secondary pests had emerged: the cotton bollworm, the cotton aphid, and the false pink bollworm. The pesticide applications rose to eight-ten per year. This reduced the problem of the aphid and the false pink bollworm but led to the emergence of five further secondary pests. By the 1960s, the original two species had become eight, and there were, on average, 28 applications of insecticide per year. Clearly, such a rate of pesticide application is not sustainable.
Chemical pesticides lose their role in sustainable agriculture if the pests evolve resistance. Pesticide resistance is almost certain to occur when vast numbers of a genetically variable population are killed. A few individuals may be unusually resistant (perhaps they possess an enzyme that can detoxify the pesticide). If the pesticide is applied repeatedly, each successive generation of the pest will contain a larger proportion of resistant individuals. Pests typically have a high intrinsic rate of reproduction. A few individuals in one generation may give rise to hundreds or thousands in the next, and resistance spreads very rapidly in a population.
This problem was often ignored in the past, even though the first case of DDT insecticide resistance was reported as early as 1946 (houseflies in Sweden). Since then, there have been exponential increases in the number of insect species resistant to insecticides. The housefly has developed resistance worldwide to virtually every chemical that has been employed against it. The evolution of pesticide resistance can be slowed, though, by changing from one pesticide to another in a repeated sequence that is rapid enough that resistance does not have time to emerge.
If chemical pesticides brought nothing but problems, however, then they would already have fallen out of widespread use. This has not happened. Instead, their rate of production has increased rapidly. The ratio of cost to benefit for the individual producer has remained in favor of pesticide use: they do what is asked of them. In the United States, insecticides are estimated to benefit the agricultural producer to the tune of around five dollars for every one dollar spent.
Moreover, in many poorer countries, the prospect of famine(extreme scarcity of food) is so frightening that the social and health costs of using pesticides have to be ignored. In general, the use of pesticides is justified by objective measures such as lives saved, economic efficiency of food production, and total food produced. In these very fundamental senses, their use may be described as sustainable. In practice, sustainability depends on continually developing new pesticides that keep at least one step ahead of the pests-pesticides that are less persistent, biodegradable, and more accurately targeted at the pests.
1
Pesticides are substances used to get rid of insects or other pests. A pesticide gets a bad name if, as is usually the case, it kills more species than just the ones at which it is aimed. It may then become a pollutant. However, in the context of the sustainability of agriculture, its bad name is especially justified if it kills the pests’ natural enemies and so contributes to undoing what it was employed to do. Thus, the numbers of a pest sometimes increase rapidly some time after the application of a pesticide. This is known as “target pest resurgence.” It occurs when treatment kills both large numbers of the pest and large numbers of their natural enemies. As a result, pest individuals that survive the pesticide or that migrate into the area later find themselves with a plentiful food resource but few, if any, natural enemies.
According to paragraph 1, what is target pest resurgence?
Factual Information Questions事实信息题
AThe survival of pests that migrated into an area where a pesticide had been applied
BThe migration of individual pests into an area that had been treated with a pesticide
CThe presence of abundant pest food after the application of a treatment
DThe increase in the numbers of a pest in an area where large numbers of the pest were previously killed by a pesticide
2
The aftereffects of applying a pesticide may involve even more subtle reactions. When a pesticide is applied, it may not be only the target pest that resurges. Alongside the target are likely to be a number of potential pest species that had been controlled by their natural enemies. If the pesticide destroys these, the potential pests become real ones-and are called secondary pests. A dramatic example concerns the insect pests of cotton in Central America. In 1950, when mass dissemination of organic insecticides(a subclassification of pesticides that kill insects) began, there were two primary pests: the Alabama leafworm and the boll weevil. Organochlorine and organophosphate insecticides were applied fewer than five times a year and initially had apparently miraculous results-yields soared. By 1955， however, three secondary pests had emerged: the cotton bollworm, the cotton aphid, and the false pink bollworm. The pesticide applications rose to eight-ten per year. This reduced the problem of the aphid and the false pink bollworm but led to the emergence of five further secondary pests. By the 1960s, the original two species had become eight, and there were, on average, 28 applications of insecticide per year. Clearly, such a rate of pesticide application is not sustainable.
Paragraph 2 suggests which of the following reasons why the cotton bollworm, the cotton aphid, and the false pink bollworm became serious problems in Central America by 1955?
Inference Questions推理题
AThe use of organochlorine and organophosphate insecticides destroyed the natural enemies of these pests
BFarmers began growing new types of cotton that attracted these pests
CThe type of insecticide needed to keep these pests under control was in,short supply at the time
DAlabama leafworm and boll weevil numbers significantly increased. which attracted secondary pests.
3
The aftereffects of applying a pesticide may involve even more subtle reactions. When a pesticide is applied, it may not be only the target pest that resurges. Alongside the target are likely to be a number of potential pest species that had been controlled by their natural enemies. If the pesticide destroys these, the potential pests become real ones-and are called secondary pests. A dramatic example concerns the insect pests of cotton in Central America. In 1950, when mass dissemination of organic insecticides(a subclassification of pesticides that kill insects) began, there were two primary pests: the Alabama leafworm and the boll weevil. Organochlorine and organophosphate insecticides were applied fewer than five times a year and initially had apparently miraculous results-yields soared. By 1955， however, three secondary pests had emerged: the cotton bollworm, the cotton aphid, and the false pink bollworm. The pesticide applications rose to eight-ten per year. This reduced the problem of the aphid and the false pink bollworm but led to the emergence of five further secondary pests. By the 1960s, the original two species had become eight, and there were, on average, 28 applications of insecticide per year. Clearly, such a rate of pesticide application is not sustainable.
According to paragraph 2, which of the following changed in the cotton fields of Central America between 1950 and the 1960s?
Factual Information Questions事实信息题
ACotton yields slowly increased.
BThe number of pest species was reduced
CThe frequency with which pesticides had to be applied increased enormously.
DPests that primarily fed on cotton plants began to feed on several secondary plants.
4
Chemical pesticides lose their role in sustainable agriculture if the pests evolve resistance. Pesticide resistance is almost certain to occur when vast numbers of a genetically variable population are killed. A few individuals may be unusually resistant (perhaps they possess an enzyme that can detoxify the pesticide). If the pesticide is applied repeatedly, each successive generation of the pest will contain a larger proportion of resistant individuals. Pests typically have a high intrinsic rate of reproduction. A few individuals in one generation may give rise to hundreds or thousands in the next, and resistance spreads very rapidly in a population.
The word ‘successive’ in the passage is closest in meaning to
Vocabulary Questions词汇题
AAffected
BHealthy
CSingle
DFollowing
5
Chemical pesticides lose their role in sustainable agriculture if the pests evolve resistance. Pesticide resistance is almost certain to occur when vast numbers of a genetically variable population are killed. A few individuals may be unusually resistant (perhaps they possess an enzyme that can detoxify the pesticide). If the pesticide is applied repeatedly, each successive generation of the pest will contain a larger proportion of resistant individuals. Pests typically have a high intrinsic rate of reproduction. A few individuals in one generation may give rise to hundreds or thousands in the next, and resistance spreads very rapidly in a population.
According to paragraph 3, how do pest populations evolve resistance to pesticides?
Factual Information Questions事实信息题
AThe rates of reproduction in the pest population rapidly increase
BThe characteristics of pesticide-resistant individuals become more common in the pest population
CA new type of enzyme evolves in individual pests after pesticides are used.
DPest populations become more genetically variable after pesticides are used.
6
Chemical pesticides lose their role in sustainable agriculture if the pests evolve resistance. Pesticide resistance is almost certain to occur when vast numbers of a genetically variable population are killed. A few individuals may be unusually resistant (perhaps they possess an enzyme that can detoxify the pesticide). If the pesticide is applied repeatedly, each successive generation of the pest will contain a larger proportion of resistant individuals. Pests typically have a high intrinsic rate of reproduction. A few individuals in one generation may give rise to hundreds or thousands in the next, and resistance spreads very rapidly in a population.
In paragraph 3, why does the author point out that pests typically have high rate of reproduction?
Factual Information Questions事实信息题
ATo help explain why resistance can spread very rapidly in a population
BTo help explain why pesticides are often applied repeatedly
CTo help explain why pest populations tend to contain vast numbers of individuals
DTo indicate a common consequence of the application of pesticides
7
If chemical pesticides brought nothing but problems, however, then they would already have fallen out of widespread use. This has not happened. Instead, their rate of production has increased rapidly. The ratio of cost to benefit for the individual producer has remained in favor of pesticide use: they do what is asked of them. In the United States, insecticides are estimated to benefit the agricultural producer to the tune of around five dollars for every one dollar spent.
The word “widespread” in the passage is closest in meaning to
Vocabulary Questions词汇题
Acommon
Bapproved
Cagricultural
Dproductive
8
Moreover, in many poorer countries, the prospect of famine(extreme scarcity of food) is so frightening that the social and health costs of using pesticides have to be ignored. In general, the use of pesticides is justified by objective measures such as lives saved, economic efficiency of food production, and total food produced. In these very fundamental senses, their use may be described as sustainable. In practice, sustainability depends on continually developing new pesticides that keep at least one step ahead of the pests-pesticides that are less persistent, biodegradable, and more accurately targeted at the pests.
Paragraph 6 suggests which of the following about the use of pesticides in many poorer countries?
Inference Questions推理题
AThe social and health costs of pesticide use in many poorer countries are too often ignored.
BThe benefits of pesticide use in many poorer countries are more important than its social and health costs
CPesticide use in many poorer countries is unsustainable by most objective measures.
DThe new pesticides being developed are often not practical in many poorer countries.
9
Moreover, in many poorer countries, the prospect of famine(extreme scarcity of food) is so frightening that the social and health costs of using pesticides have to be ignored.[■] In general, the use of pesticides is justified by objective measures such as lives saved, economic efficiency of food production, and total food produced. [■]In these very fundamental senses, their use may be described as sustainable.[■] In practice, sustainability depends on continually developing new pesticides that keep at least one step ahead of the pests-pesticides that are less persistent, biodegradable, and more accurately targeted at the pests.[■]
Look at the four squares[■] that indicate where the following sentence could be added to the passage
Thus the need for new and better pesticides is unending.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
The effects of pesticide use have been widely debated.
Prose Summary Questions概要小结题
Select 3 answers
APesticides often kill a pest’s natural enemies, which may eventually lead not only to the increase in the numbers of the target pest population but also to the emergence of secondary pests.
BSome pesticides may be classified as pollutants if they allow individual pests to survive the pesticide and migrate to another area to find new food resources.
CPesticides have been successfully used against houseflies and pests of cotton, but they proved ineffective against other pests, which is why the worldwide production of pesticides has slowed.
DIt is necessary to constantly develop new pesticides because a pest typically develops pesticide resistance if the same chemical is repeatedly used to kill that pest.
EPesticide use can be profitable for agricultural producers, can increase the supply of food, and can be sustainable if the pesticide is biodegradability and does not kill species other than the target pests.
FThe events in Central America in the 1950s are a dramatic example of the extremely high social and heath costs that pesticide use can have in some poorer countries.
