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  3. PEST CONTROL (1) Many pest species that are native to North America, such as white-footed mice and ground moles, are more nu

PEST CONTROL (1) Many pest species that are native to North America, such as white-footed mice and ground moles, are more nu

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问题                                                 PEST CONTROL
    (1) Many pest species that are native to North America, such as white-footed mice and ground moles, are more nuisance pests and are usually regulated by native predators and parasites. This situation is not true for non-indigenous pests in North America, such as brown rats and cockroaches. After centuries, it is evident that these pests cannot be eradicated. The best that can be done is to introduce pest control measures that will control their numbers.
    (2) An ancient and popular means of pest control is chemical control. For example, the Sumerians used sulfur to combat crop pests, and by the early 1800s such chemicals as arsenic were used to combat insect and fungal pests.
    (3) However, chemical control has its dark side. Chemical pesticides have many unintended consequences through their effects not just on the target species but. on a wide array of non-target species as well, often eliminating them and thereby upsetting the existing food webs, especially through the suppression of native predator species. The surviving pests then rebound in greater numbers than ever.
    (4) Perhaps more insidious is that a pesticide loses its effectiveness because the target species evolves resistance to it. As one pesticide replaces another, the pests acquire a resistance to them all. [A] Some species, notably certain mosquitoes, have overcome the toxic effects of every pesticide to which they have been exposed. [B] Insect pests need only about five years to evolve pesticide resistance, but their predators do so much more slowly. [C] So after the pests develop resistance, pest outbreaks become even more disastrous. [D]
    (5) Farmers long ago observed that enemies of pests act as controls. As early as 300 A.D., the Chinese were introducing predatory ants into their citrus orchards to control leaf-eating caterpillars. Insect pests have their own array of enemies in their native habitats. When an animal or plant is introduced, intentionally or unintentionally, into a new habitat outside of its natural range, it may adapt to the new environment and leave its enemies behind. Freed from predation and finding an abundance of resources, the species quickly becomes a pest or a weed. This fact had led to the search for natural enemies to introduce into populations of pests to reduce their populations.
    (6) Because the serious pest is usually a nonnative species, biological control involves the introduction of a non-indigenous predator or parasite to control the pest. The introduction of the cactus-eating moths, a native of Argentina, into Australia effectively reduced and controlled the rapidly spreading prickly pear, which had been introduced into Australia in 1901.
    (7) But biological control, like chemical control, can backfire. The success of the cactus-feeding moths in controlling prickly pear in Australia encouraged their introduction to several West Indies islands to control prickly pear there. In time the moths made their way to Florida, where they now threaten the existence of several native prickly pear species. The moral is that although using non-indigenous predators as biological controls can be effective, these species possess their own inherent dangers that must be assessed before they are released. They, too, can become alien invaders.
    (8) Because chemical, biological, and other methods used individually are obviously not the solution to pest control, entomologists have developed a holistic approach to pest control, called integrated pest management (IPM). IPM considers the biological, ecological, economic, social, and even aesthetic aspects of pest control and employs a variety of techniques. The objective of IPM is to control the pests not at the time of a major outbreak but at an earlier time when the size of the population is easier to control. The approach is to rely first on natural mortality caused by weather and natural enemies, with as little disruption of the natural system as possible, and to use other methods only if they are needed to hold the pests below the economic injury level.
    (9) Successful IPM requires the knowledge of the population ecology of each pest and its associated species and the dynamics of the host species. It involves considerable field work monitoring the pest species and its natural enemies by such techniques as egg counts and the trapping of adults to acquire information to determine the necessity, timing, and intensity of control measures. These control measures must be adjusted to the situation, which may vary from one location to another. The intensity of control or no control is based on the degree of pest damage that can be tolerated, the costs of control, and the benefits to be derived.
An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
Pest control measures vary in their approach and overall degree of success.
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Answer Choices
(A) Biological methods of pest control were introduced by the ancient Sumerians, and chemical control was first used in ancient China
(B) Biological control, for example, the use of natural enemies of pests, has been effective at regulating normative pests, though it can also threaten the existence of native species.
(C) Integrated pest management is a holistic approach that has been successful at controlling major pest outbreaks in locations where chemical and biological control have already failed.
(D) Pesticides are limited in their usefulness because pests quickly become resistant to them, and because they can harm species for which they were not intended.
(E) The success of biological and chemical approaches to pest control has been difficult to measure because situations vary significantly from one location to another.
(F) Integrated pest management, an approach that consider biological, ecological, economic, and aesthetic aspects of pest control, uses a variety of techniques adjusted to specific situations.
选项
答案B,D,F
解析 本题属于文章总结题。B项“生物控制的手段，如利用害虫的自然天敌，在控制非本地害虫上十分有效，尽管这同时也可能会给当地物种的生存带来威胁”是对第6、7段的整合。D项“杀虫剂的有效性是有限的，因为害虫很快能够对其产生抗药性，也因为杀虫剂会不小心错杀其他物种”是对第3段的整合。F项“害虫综合治理是一种考虑了生物、生态、经济和美学的害虫控制方法，使用不同的技术来应对特定情况”是对第8、9段的整合。B、D、F三项介绍的是不同的害虫控制方法及其有效程度，三项均为文章的主要观点。A项“古苏美尔人采用生物手段来控制害虫，而化学控制最先在中国古代被运用”张冠李戴，由第2段可知，苏美尔人用的是化学手段；由第5段可知，中国古代用的是生物手段。C项“害虫综合治理是一种整体的(害虫控制)方法，在一些化学和生物控制都无法解决大规模害虫爆发的地方成功实现了治理”没有依据。E项“很难衡量害虫控制的生物和化学方法是否有效，因为不同地方的情况差异很大”，原文第8段明确指出，化学控制和生物控制不是控制害虫的有效解决方案，所以昆虫学家提出了一种整体的解决办法——IPM，E项与文章表述不符。
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